Table 1 Parameters for acquisition and analysis of ultrasound images during feeding

Wilbur L. et al. (1988-USA) [11]

To describe the behavior of the nipple during feeding and the dynamics of normal baby feeding with US

Breastfeeding

16 mothers and babies Age: 60 to 120 days

Transducer not specified

Frequency: 5 MHz

B mode

Parameters not specified

Measurements were taken from a display using a manual caliper

Not specified

The transducer was positioned in the horizontal transoral axial plane (under the cheek) to visualize nipple compression during sucking

To visualize the length of the nipple, the transducer was positioned centrally under the baby’s chin, in the sagittal plane under the submental region aligned with the nipple, which was positioned to the left

The dietary pattern of each infant was observed by stop-frame visual analysis of nipple deformation and changes in shape and position of the tongue, cheeks, and palate

Milk flow was visualized as hypoechoic fluid containing echogenic spots

The examination began when the baby latched onto the breast and ended when there was a decrease in milk intake seen on the ultrasound image

Three complete suction cycles were performed

Nipple Stretching (Submental Vision):

Nipple elongation (dark/gray region) was obtained with the ratio of the length at the end of sucking to the total extension of the intraoral nipple

Nipple compression (horizontal plane):

Lateral (transverse) compression of the nipple was also recorded as a ratio of the undeformed nipple width to the maximum deformed width

Maximum compression:

The height of the nipple is reduced by half due to compression between the tongue and palate. Milk ejection occurs after maximum nipple compression

Jacobs, AL et al. (2007-Australia)[12]

To assess the distance from the nipple to the junction of the hard and soft palate and the movement of the nipple during sucking in full-term babies using US

Breastfeeding

18 mothers and babies

Age: 3 to 14 days (assessment);

25 to 65 days (reassessment)

1—Convex Endocavity Transducer (used in 65% of babies)

Frequency: 7 MHz

2- Sector phased array transducer (used in 30% of babies)

Frequency: 7 MHz

3- Linear array transducer (used in 5% of babies)

Frequency: 7 MHz

B mode

Gain: 50 dB

Dynamic range: 50 to 57 dB

It used a short, nipple-level depth and adjusted dynamic range to optimize soft tissue detail

Software, ViewScan, was created and used to extract ultrasound images from videotape recording, record, and measure distances between manually selected anatomical points

The investigator marked the anatomy on ultrasound images on the computer screen with a mouse pointer, and ViewScan

recorded the distance between the marks in pixels that were converted into millimeters

The mother sat next to the US device and positioned and latched the baby as determined by the International Board Certified Lactation Consultant (IBCLC)

The transducer was positioned centrally under the baby’s chin, in the sagittal plane under the submental region aligned with the nipple, which was positioned on the left

The hard palate appears as an echogenic (white) line area, while the soft palate appears as a gray structure with an echogenic border. The nipple appears as a gray (cylindrical, “finger-like”) structure and the milk ducts within the nipple appear as thin hypoechoic (black) tubular structures. Milk flow was visualized as hypoechoic fluid containing echogenic spots

They were advised not to breastfeed 2 h before the exam

The exam started when the baby latched onto the breast and ended after about 5 min

The 5 min were subdivided into T0 (first visible suction between the beginning of the feeding and the end of the first minute to record feeding events and nipple position before); T2 (second minute to record feeding events) and T5 (when sucking may be different because at least 80% of the volume of a breastfeed is

consumed in the first 4 min)

Nipple diameter:

Distance (mm) traveled by the entire gray structure presented cylindrically in the image

Distance from the beak to the hard-soft palate junction:

Distance (mm) between the tip of the nipple and the beginning of the hard-soft palate junction was measured from a transverse mark on the tip of the nipple to the transverse mark on the distal end of the hard palate adjacent to the soft palate in the sagittal plane

The distance between the tip of the nipple and the hard palate and soft palate junction was measured in the midsagittal anatomical plane

Geddes DT et al. (2008 -

Australia)[9]

To examine the relationship between tongue movement and intraoral vacuum generated during breastfeeding by the baby

Breastfeeding

20 mothers and babies

Age: 3 to 24 weeks

1—Endocavity Convex Transducer

Frequency: 7 MHz

2—PVT- 661 VT Convex Transducer

Frequency: 8.8 MHz

In some bigger and older babies, the transducer frequency was reduced

(8.8 MHz to 7.3 or 5.8 MHz) for a better image

B mode

1—Gain: 50 dB

Dynamic range: 57 dB

2 – Gain: 55 dB

Dynamic range: 60 dB

Two foci were used to narrow the ultrasound beam:

One on the hard palate and the other on the nipple-tongue attachment

Adjustments were made to gain, dynamic range, and timing during the acquisition

Not specified

The transducer was positioned along the midsagittal line of the baby’s body and gentle pressure was used to maintain contact with the baby’s chin

The transducer was rotated until the image of the nipple was at its maximum length and diameter and a view of the junction of the hard and soft palate was achieved

The position of the transducer was changed according to the baby’s movement to maintain a midline sagittal view

The hard palate appears as an echogenic (white) line area, while the soft palate appears as a gray (3–4 mm) structure with an echogenic border. The nipple appears as a gray (cylindrical) structure and the milk ducts within the nipple appear as thin hypoechoic (black) tubular structures. Milk flow was visualized as hypoechoic fluid containing echogenic spots. Echogenic spots are fat globules in milk

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding

At least three complete sucking cycles were performed during which milk flow was evident on the ultrasound image

Tongue position during the sucking cycle:

Initially, the posterior region of the tongue is observed attached to the palate (upward position), and the anterior region of the tongue is attached to the lower edge of the nipple

When the posterior region of the tongue is lowered to the maximum, the vacuum peak occurs. As the vacuum is released, the anterior region of the tongue is elevated slightly, and the milk passes under the soft palate. Both the back of the tongue and the soft palate rise, and milk continues to flow towards the pharyngeal region. When the posterior region reaches the palate (up position) the vacuum returns to basal levels

Nipple diameter:

Distance (mm) traveled by the entire gray structure presented cylindrically in the image

Distance from the nipple to the hard-soft palate junction:

Distance (mm) between the tip of the nipple and the beginning of the hard-soft palate junction

Distance between tongue and palate:

Distance (mm) from the hard palate to the surface of the posterior region of the tongue. Its maximum distance corresponds with the vacuum peak

Geddes, DT et al. (2008- USA) [13]

To determine the effectiveness of frenotomy by measuring milk transfer and tongue movement during breastfeeding

Breastfeeding

24 mothers and babies

Age: 4 to 131 days (assessment);

22 to 150 days (reassessment)

Endocavity Convex Transducer

Frequency: 7 MHz

B mode

Gain: 5 dB

Dynamic range: 57 dB

Single focus adjusted to nipple level

Adjustments were made to gain, dynamic range, and timing during the acquisition

Not specified

The transducer was positioned along the midsagittal line of the baby’s body

The transducer was rotated until the image of the nipple was at its maximum length and diameter and a view of the junction of the hard and soft palate was achieved

Measurements were taken at 2 points in each suction cycle. The first point on the tongue is most positioned in attachment to the hard palate, and the second with the tongue down, with evident milk flow

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding

At least five complete sucking cycles were performed during which milk flow was evident on the ultrasound image

Distance from the nipple to the hard-soft palate junction:

Distance (mm) between the tip of the nipple and the beginning of the hard-soft palate junction

Nipple diameter:

Distance (mm) traveled by the entire gray structure presented cylindrically in the image

Average range of nipple movement:

Difference in the junction of the nipple and hard/soft palate between the tongue up and tongue down positions for the 5 sucking cycles

Geddes, DT et al. (2010- Australia)[14]

To assess the sucking characteristics of normal infants

Breastfeeding

5 mothers and babies

Age: 21 to 52 days

Endocavity Convex Transducer

Frequency: 7 MHz

B mode

Gain: 50 dB

Dynamic range: 57 dB

Not specified

The transducer was positioned along the midsagittal line of the baby’s body

The transducer was rotated until the image of the nipple was at its maximum length and diameter and a view of the junction of the hard and soft palate was achieved

The hard palate appears as an echogenic (white) line area, while the soft palate appears as a gray structure with an echogenic border. The nipple appears as a gray (cylindrical) structure

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding

At least three complete sucking cycles were performed during which milk flow was evident on the ultrasound image

Tongue position during normal breastfeeding:

The tongue is attached to the soft palate. The tongue compresses the nipple evenly. As the tongue is lowered inferiorly, the nipple expands in diameter and approaches the hard-soft palate junction. There is no nipple distortion

Tongue position during breastfeeding in a baby with ankyloglossia:

Tongue upward pattern, without nipple distortion. Tongue down, with compression of the base of the nipple. Tongue up, with compression of the tip of the nipple. Tongue down, without nipple distortion

McClellan HL et al. (2010- Australia)[15]

To measure the distance from the junction between the hard palate and the tongue up and down

Breastfeeding

30 mothers and babies

Age: mean of 56.3 days

PVT- 661 VT Convex Transducer

Frequency: 7.3 MHz to 8.8 MHz

In some bigger and older babies, the transducer frequency was reduced (8.8 MHz to 7.3 or 5.8 MHz) for a better image

B mode

Gain: 55 dB

Dynamic range: 60 dB

Two foci were used to narrow the ultrasound beam:

One on the hard palate and the other on the nipple-tongue attachment

Adjustments were made to gain, dynamic range, and timing during the acquisition

Not specified

The transducer was positioned along the midsagittal line of the infant’s head and light pressure was used to maintain contact with the infant’s chin

The images were oriented so that the nipple was always on the left side of the image

The transducer was rotated until the image of the nipple was at its maximum length and diameter and a view of the junction of the hard and soft palate was achieved

The position of the transducer was changed according to the baby’s movement to maintain a midline sagittal view

The soft palate appeared as a medium-gray structure with an echogenic upper border. The hard (bony) palate appeared as an echogenic white line

Two calipers were used to measure the diameter of the nipple; the first measured the gap along the tip of the nipple (10 mm). The second caliper measured the outer diameter of the nipple at each interval

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding

At least one suction cycle was included

Depth:

Depth is measured as the internal distance from the hard palate to the tongue. The calipers measured the depth of the space in which the milk flowed into the pharynx

Tongue position during the sucking cycle:

Tongue up: when the tongue is raised as much as possible; the tongue is attached to the nipple, the hard and soft palate, and their junction. In this position, the shortest distance from the tip of the nipple to the hard and soft palate junction was obtained

Tongue down: the tongue is lowered to its lowest level from the hard and soft palate junction. The tongue is attached to the nipple and soft palate, but not to the hard palate. In this position, the shortest distance from the tip of the nipple to the depth axis was obtained

Nipple diameter:

Distance (mm) traveled by the entire gray structure presented cylindrically in the image

Distance from the nipple to the hard-soft palate junction:

Distance (mm) between the tip of the nipple and the beginning of the hard-soft palate junction

Sakalidis VS et al. (2013- Australia)[16]

To describe infant sucking patterns during breastfeeding at the time of secretory activation

Breastfeeding

15 mothers and babies

Age: 3.2 to 16 days

Endocavity transducer

Frequency: 5–8 MHz

In some bigger and older babies, the transducer frequency was reduced (8.8 MHz to 7.3 MHz) for a better image

B mode

Gain: 55 dB

Dynamic range: 60 dB

Two foci were used to narrow the ultrasound beam:

One on the hard palate and the other on the nipple-tongue attachment

Adjustments were made to gain, dynamic range, and timing during the acquisition

Not specified

The transducer was positioned along the midsagittal line of the infant’s head, and light pressure was used to maintain contact with the infant’s chin

The transducer was rotated until the image of the nipple was at its maximum length and diameter and a view of the junction of the hard and soft palate was achieved

The tip of the tongue could not be visualized using this method

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding

Images from three consecutive cycles during NS and NNS were selected. Analysis done with the tongue up and tongue down

First breastfeeding assessment carried out on the 3rd day postpartum (range 2–4), in the hospital or at the mother’s home

Second assessment of breastfeeding between days 10 and 45 postpartum (follow-up), carried out at the mother’s home

Suction cycle:

Defined as the beginning when the middle of the tongue was attached to the palate (tongue up), followed by a downward excursion of the tongue until when the middle tongue reached its lowest point (tongue down) and ending with the tongue attached to the palate again

Suction Rates:

Determined by counting the number of suctions per burst in the ultrasound record in the first 3 and last 3 min of feeding. A burst was defined as periods of sucking (tongue movement) between pauses (tongue rest)

Nutritive Suction (NS):

Suction cycles that resulted in the delivery of milk to the oral cavity, observed on US, in which the milk bolus appeared as a hypoechoic area (black) filled with echogenic spots (white)

Nonnutritive Sucking (NNS):

Suction cycles in which there was no milk on the ultrasound image

Tongue position in NS:

Tongue up: The nipple is evenly compressed from tip to base, and the tongue is in contact with the hard and soft palate

Tongue down: The nipple expands evenly in size, approaching the hard-soft palate junction, the middle of the tongue low, allowing milk to flow into the intraoral space

Tongue position in NNS:

Tongue up: The nipple is less compressed compared to the same position in NS

Tongue down: The nipple expands to a lesser extent, and the middle tongue lowers to a lesser extent in relation to NS

Depth of the intraoral space: distance from the hard-soft palate junction to the posterior surface of the tongue and distance from the tip of the nipple to the hard-soft palate junction

Sakalidis VS et al. (2013- Australia)[17]

To measure sucking behavior in newborn infants born by cesarean section or vaginal delivery during secretory activation and after lactation

Breastfeeding

14 mothers and babies

Age: 3 to 20 days

Endocavity transducer

Frequency: 5 to 8 MHz

B mode

Gain: 55 dB

Dynamic range: 60 dB

Two foci were used to narrow the ultrasound beam:

One on the hard palate and the other on the nipple-tongue attachment

Adjustments were made to gain, dynamic range, and timing during the acquisition

Not specified

The transducer was positioned along the midsagittal line of the infant’s head and light pressure was used to maintain contact with the infant’s chin

The transducer was rotated until the image of the nipple was at its maximum length and diameter and a view of the junction of the hard and soft palate was achieved

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding

At least three complete sucking cycles were performed during which milk flow was evident on the ultrasound image

Breastfeeding assessments were carried out in two stages:

The first in secretory activity (Day 3; interval, 2–4 days postpartum), carried out in the hospital or at the mother’s home

The second (monitoring), during established lactation (interval, 10–45 days postpartum), at the mother’s home

In each session, ultrasound images of the infant’s intraoral cavity were recorded during breastfeeding to determine tongue movement

Tongue position during the sucking cycle:

Beginning when the middle tongue was attached to the palate (tongue up) followed by a downward excursion of the tongue until the middle tongue reached its lowest point (tongue down) and ending with the tongue attached to the palate again

Nutritive suction:

Suction cycles resulting in delivery of milk into the oral cavity as imaged by ultrasound where the milk bolus appeared as hypoechoic

Nonnutritive suction:

Defined as sucking cycles in which no milk was observed in the intraoral cavity on ultrasound

McClellan, HL et al. (2015-Australia)[18]

To analyze the intraoral shape of the nipple and tongue movement in babies of mothers with and without nipple pain

Breastfeeding

50 mothers and babies. (25 Control Group (CG) and 25 Pain Group PG)

Age: CG 48 days (35–61)

PG 46 days (30–70)

PVT- 661 VT endocavity convex transducer

Frequency: 8.8 MHz

B mode

Gain: 55 dB

Dynamic range: 60 dB

Two foci were used to narrow the ultrasound beam:

One on the hard palate and the other on the nipple-tongue attachment

The images were oriented so that the nipple was

always on the left side and at the top of the image

Two images were selected from each of the three sucking cycles: one when the middle tongue was raised to its highest level (tongue up), and the second when the middle tongue was lowered to its maximum (tongue down)

Babies breastfeeding with mothers sitting comfortably using a breastfeeding pillow

The transducer was positioned along the midsagittal line of the baby’s body and gentle pressure was used to maintain contact with the baby’s chin

Infant’s intraoral cavity with the outline of the tongue marked in white

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding

At least three complete sucking cycles were performed during which milk flow was evident on the ultrasound image

Depth of the intraoral space:

Distance from the hard-soft palate junction to the posterior surface of the tongue and distance from the tip of the nipple to the hard-soft palate junction

Tongue up:

The tongue moved inferiorly, with the middle tongue showing greater displacement as it moved away from the hard-soft palate junction

Tongue down:

The middle tongue was at its lowest point, the middle tongue elevated sequentially in an anteroposterior manner

The soft palate followed the posterior tongue as it moved inferiorly with the middle tongue, and as the middle tongue returned to the hard palate, milk could be seen passing under the soft palate in two frames

Cannon AM et al. (2016- Australia)[4]

To investigate the parameters of the infant’s sucking cycle in relation to the volume of milk removed from the breast

Breastfeeding

19 mothers and babies

Age: 36 ± 21 days (9–74)

PVT- 661 VT endocavity convex transducer

Frequency: 8.8 MHZ

B mode

Parameters not specified

Not specified

The transducer was positioned along the midsagittal line of the baby’s body and gentle pressure was used to maintain contact with the baby’s chin

The transducer was rotated until the image of the nipple was at its maximum length and diameter and a view of the junction of the hard and soft palate and tongue was achieved

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding, on the first breast

The first 4 min of the NS cycle were determined by the presence of milk in the infant’s intraoral cavity identified in the ultrasound images, and multiple swallows identified in the breathing trace

Tongue position during the sucking cycle:

During the first half of the cycle, the middle tongue is in contact with the palate, and a basal vacuum is applied. As the tongue lowers, the vacuum increases and milk flows into the oral cavity

During the second half of the cycle, the vacuum decreases as the tongue moves upward and milk is eliminated from the oral cavity into the pharynx for swallowing and the vacuum returns to baseline levels, thus completing a sucking cycle

Alatalo D et al. (2020-USA)[6]

To investigate positive oral pressures exerted by the baby during breastfeeding and compare them with negative vacuum pressures from the same feeding

Breastfeeding

6 mothers and babies

Age: 6 to 18 weeks

Endocavity Convex Transducer

Frequency: 7 MHz

In some bigger and older babies, the transducer frequency was reduced (8.8 MHz to 7.3 or 5.8 MHz) for a better image

B mode

Gain: 55 dB

Dynamic range: 60 dB

Two foci were used to narrow the ultrasound beam:

One on the hard palate and the other on the nipple-tongue attachment

Adjustments were made to gain, dynamic range, and timing during the acquisition

All infants were successfully breastfed using a nipple shield

The mother was asked to demonstrate how she would hold the baby and was instructed to bring the baby’s jaw, mandible, and lips closer together during sucking

The transducer was positioned along the midsagittal line of the baby’s body and gentle pressure was used to maintain contact with the baby’s chin

The transducer was rotated until the image of the nipple was at its maximum length and diameter and a view of the junction of the hard and soft palate was achieved

The position of the transducer was changed according to the baby’s movement to maintain a midline sagittal view

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding

At least three complete sucking cycles were performed during which milk flow was evident on the ultrasound image

Tongue position during the sucking cycle:

The tongue, hard palate, and soft palate surround the nipple during milk ejection in a sucking cycle. The wave-like movement of the tongue anterior to the baby’s palate was visualized. The nipple was visibly elongated and compressed when the babies moved their tongues up and down

Nipple width and length:

Maximum nipple width and minimum nipple length were observed when the baby’s tongue moved to the lowest position in nutritive sucking. A large portion of the areola must be pulled into the oral cavity so that the nipple reaches the junction of the soft and hard palate

The nipple was assumed to be cylindrical in shape and pre-feeding and post-feeding measurements were used to calculate volume changes. The difference between pre-feed and post-feed volumes is reported as the volume change. Two separate measurements were averaged to calculate pre-feeding and post-feeding nipple width and length

Douglas PS et al. (2022- Australia)[8]

To investigate whether Gestalt intervention modifies nipple placement, tongue position and shape, and dimensions of the nipple and breast tissue during breastfeeding

Breastfeeding

4 mothers and babies

Age: 2 to 20 weeks

Endocavity convex transducer 6 V1/11

Frequency: 8.8 MHZ

B mode

Gain: 55 dB

Dynamic range: 60 dB

Two foci were used to narrow the ultrasound beam:

One on the hard palate and the other on the nipple-tongue attachment

Adjustments were made to gain, dynamic range, and timing during the acquisition

First moment: babies breastfed with support from a breastfeeding consultant

Second moment: Gestalt intervention between 5 and 10 min

The transducer was positioned along the midsagittal line of the baby’s body and gentle pressure was used to maintain contact with the baby’s chin

The transducer was rotated until the image of the nipple was at its maximum length and diameter and a view of the junction of the hard and soft palate was achieved

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding

At least three complete sucking cycles were performed during which milk flow was evident on the ultrasound image

Tongue position during the sucking cycle:

Initially, the posterior region of the tongue is observed attached to the hard palate, the hard-soft palate junction, and the soft palate (positioned upwards), and the anterior region of the tongue attached to the lower edge of the nipple, sealing the oral cavity and pharynx, generating the basal vacuum

Intraoral space:

It is limited distally by the tip of the nipple, proximally by the soft palate attached to the base of the tongue, superiorly by the hard palate, and inferiorly by the dorsal surface of the tongue, and does not contain air

Distance from the beak to the hard-soft palate junction:

Distance (mm) between the tip of the nipple and the beginning of the hard-soft palate junction

Distance between the tongue and hard palate:

Distance (mm) from the hard palate to the surface of the posterior region of the tongue. Its maximum distance corresponds to the vacuum peak

Alan A et al. (2023- Turkey)[19]

To compare the position and movement of the tongue during sucking in babies with and without ankyloglossia

Breastfeeding

30 mothers and babies without ankyloglossia

30 mothers and babies with ankyloglossia

Age: 5 to 15 days

8 C-RS micro-convex transducer. To acquire 2D images

Frequency: 6–10 MHz

B and M modes

Gain: 55 dB

Dynamic range: 60 dB

Two foci were used to narrow the ultrasound beam:

One on the hard palate and the other on the nipple-tongue attachment

Adjustments were made to gain, dynamic range, and timing during the acquisition

Not specified

The transducer was positioned along the midsagittal line of the baby’s body and gentle pressure was used to maintain contact with the baby’s chin

Visibility of the tip of the tongue on ultrasound is impaired by mandibular superposition

The hard palate appears as an echogenic (white) line area, while the soft palate is observed as an intermediate gray structure with a distinct echogenic upper border. The nipple appears as a gray (cylindrical) structure

B-Mode ultrasound images:

Used to examine various features to locate the nipple in the oral cavity during breastfeeding

M-mode ultrasound images:

Anatomical ultrasound images were used to evaluate tongue movement during sucking

The exam started when the baby latched on to the breast and ended when the baby finished breastfeeding

Tongue position during sucking:

Initially, the posterior region of the tongue is observed attached to the palate (upward position), and the anterior region of the tongue attached to the lower edge of the nipple. When the posterior region of the tongue is lowered to the maximum, the vacuum peak occurs. As the vacuum is released, the anterior region of the tongue is elevated slightly, and the milk passes under the soft palate. Both the back of the tongue and the soft palate rise, and milk continues to flow towards the pharyngeal region. When the posterior region reaches the palate (upward position) the milk is introduced into the pharynx

Distance from the nipple to the hard-soft palate junction:

Distance (mm) between the tip of the nipple and the beginning of the hard-soft palate junction

Nipple position during breastfeeding:

The nipple is positioned so that it rests against the anterior region of the tongue, while the tip of the anterior tongue is elevated above the inferior alveolar ridge

Weber F et al. (1986-

England)[20]

To describe events that occur in the baby’s oral cavity during breastfeeding using US

Breastfeeding and bottle

6 mothers and babies (mother’s breast)

6 babies (bottle)

Age: 2 to 6 days

Transducer: Not specified

Frequency: not specified

B mode

Depth 6.6 cm

Other parameters not specified

Bottle: baby held by the mother, who supported and slightly tilted his head

Maternal breast: baby placed in the usual position

The transducer was positioned along the midsagittal line of the baby’s body and gentle pressure was used to maintain contact with the baby’s chin

The image is best seen when tilted 45º so that the baby’s head is vertical

The hard palate appears as an echogenic (white) line area, while the soft palate appears as a gray structure with an echogenic border. The nipple appears as a gray (cylindrical) structure. The structures seen at the back of the mouth, behind the tongue, are assumed to be the upper margin of the larynx

The examination began when the baby took the breast and bottle and ended when the baby finished feeding

Coordination of sucking and swallowing:

Sucking is evident from the beginning of the tongue indentation of the nipple or bottle nipple. Sucking is the isolated action of tongue movement without laryngeal movement and"suction-swallowing"for sucking accompanied by swallowing

Tongue position during the sucking cycle:

Maternal breast: tongue movement was wavelike; and in the resting position of the tongue, the nipple was recessed

Baby bottle: the movement seemed to be due to compression, and in the resting position of the tongue the nipple was expanded

Geddes DT et al. (2012-

Australia)[7]

To determine the action of the infant’s tongue during breastfeeding and bottle feeding using US

Breastfeeding and bottle

12 mothers and babies (mother’s breast)

6 babies (trial bottle)

Age: 49.4 days (+ − 19.9) mother’s breast

56 days (+ − 18.3) bottle

Transducer: endocavity convex (PVT- 661 VT)

Frequency:

3.6–9 MHz

B mode

Parameters not specified

Two foci were used to narrow the ultrasound beam:

One on the hard palate and the other on the nipple-tongue attachment

Adjustments were made to gain, dynamic range, and timing during the acquisition

Bottle: offered by the mother

Breast: baby placed in the usual position

The transducer was positioned along the midsagittal line of the baby’s body and gentle pressure was used to maintain contact with the baby’s chin

The transducer was rotated until the image of the nipple was at its maximum length and diameter and a view of the junction of the hard and soft palate was achieved

The position of the transducer was changed according to the baby’s movement to maintain a midline sagittal view

The hard palate appears as an echogenic (white) line area, while the soft palate appears as a gray structure with an echogenic border. The nipple appears as a gray (cylindrical) structure and the milk ducts within the nipple appear as thin hypoechoic (black) tubular structures visible when the tongue is lowered in breastfeeding

Mothers were asked to measure 24-h milk production in their own homes

Mothers and babies attended to the laboratory in two moments with an interval of 15 days between them

The examination began when the baby took the breast and bottle and ended when the baby finished feeding

Tongue position during the sucking cycle:

In the first half of the sucking cycle, as the tongue lowered, the intraoral vacuum increased, and milk flowed into the mouth during breastfeeding and experimental bottle feeding

In the second half of the sucking cycle, as the tongue rose, milk was eliminated from the oral cavity (the anterior tongue rose a little earlier than the rest of the tongue) towards the palate, and the vacuum decreased

To compare tongue movement, the relationship between nipple diameter and the interaction between tip distance, tongue position, and type of feeding was considered; 5 mm was designated as the reference level

Distance from the nipple to the hard-soft palate junction:

Distance (mm) between the tip of the nipple and the beginning of the hard-soft palate junction

Nipple diameters:

Distance (mm) traveled by the entire gray structure presented cylindrically in the image

Measured at intervals of 2, 5, 10, and 15 mm from the tip of the nipple to the base of the nipple. Such measurements were made with two calipers: one to measure the intervals along the nipple from the tip and the other to measure the external diameter of the nipple at each interval. There was an increase in the diameter of the nipple and the bottle nipple, except for the tip of the nipple with the tongue pointing upwards

Nowak AJ et al. (1994-USA)[22]

To compare differences in deformation of the bottle nipple with the human nipple and compare the suction mechanism used by the infant using US

Bottle feeding

35 babies

Age: 6–12 weeks

E8 C-RS endocavity transducer

Frequency: 5 MHz

B mode

Parameters not specified

Not specified

The transducer was positioned in the coronal plane, along the midsagittal line of the baby’s body, submental region, with minimal interference to the baby’s chin

The transducer was positioned in the axial plane (transoral approach through the cheek)

In this axis, the nipple was observed just after its full extension. The echogenic material at the tip of the nipple is milk and air extracted from the nipple

Several 3-s ultrasound cine-clips were recorded as soon as the baby began nutritive sucking

The examination began when the baby took the bottle and ended when the baby finished feeding

At least three complete sucking cycles were performed during which milk flow was evident on the ultrasound image

In the axial plane:

The ratio of the length of the nipple during full suction to the length of the nipple at rest

The ratio of the nipple width at full suction to the nipple width at rest provides a measurement of lateral (side-to-side) compression

On the coronal axis:

Measuring the degree of flattening of the nipple is equivalent to the ratio between the height of the nipple at maximum compression and the height of the nipple at rest

Deformation of the nipples and changes in the shape and position of the tongue, cheeks, and soft palate were observed by stop-frame analysis during each infant’s feeding pattern

Nowak AJ et al. (1995-USA)[21]

To compare the sucking and swallowing patterns of infants while feeding with a new bottle nipple during breastfeeding

Bottle feeding

15 babies

Age: 2 to 15 weeks

(mean of 7.2)

Transducer: angled

Frequency: 5 MHz

B mode

Parameters not specified

Supine in a crib or on a plank table with the neck in slight hyperextension

The transducer was positioned in the coronal plane, along the midsagittal line of the baby’s body, submental region, with minimal interference to the baby’s chin

The transducer was positioned in the axial plane (transoral approach through the cheek)

In this axis, the nipple was observed just after its full extension. The echogenic material at the tip of the nipple is milk and air extracted from the nipple

Parents were asked to use the new tricut bottle nipple and return after 1 week of successful feeding

Serve milk in a bottle for 2 min

At least three complete sucking cycles were performed during which milk flow was evident on the ultrasound image

In the axial view:

Length of the anterior to posterior region of the tongue and compression of the nipple were observed

The ratio of the nipple width at full suction to the nipple width at rest provides a measurement of lateral (side-to-side) compression

In the coronal view:

Medial compression of the nipple was observed. Length, anteroposterior compression, and medial compression of the beak were measured

Hayashi N et al. (1997-Japan)[23]

to observe morphological and suction pressure analysis simultaneously using US in M and B modes

Bottle feeding

15 babies

Age: 5 to 6 days

Transducer: Not specified

Frequency: 5 MHz

B and M modes

Parameters not specified

Not specified

The transducer was positioned along the midsagittal line of the baby’s body, the submental region

The examination began when the baby took the bottle and ended when the baby finished feeding

Tongue position during the sucking cycle:

Initially, the anterior portion of the tongue pressed the nipple upward and the medial portion pressed the nipple when the anterior portion moved downward

The posterior portion moved upward in order, pressed against the palate again, and then moved downward and separated from the palate

In B-mode ultrasound:

The space surrounded by the posterior portion of the tongue, palate, and nipple disappeared when the tongue was attached to the palate and increased in size when the tongue moved downward and separated from the palate

In M-mode ultrasound:

In the line that includes the posterior portion of the tongue and the palate, a linear pattern was observed while the tongue was attached to the palate. When the tongue was separated from the palate and moved downward, the distance between the posterior portion of the tongue and the palate became greater

With the anteroposterior wave movement, the tongue rose again, and the distance between the posterior portion of the tongue and the palate became smaller

This distance changed moment by moment, and sequential changes in distance were observed as a rectilinear pattern

With the letdown of milk, the posterior portion of the tongue moves downwards and releases the palate and the space surrounded by the posterior portion of the tongue. The nipple and palate appear, and the nipple increases in size

Lagarde L et al. (2021- the Netherlands)[24]

To measure nipple compression and tongue movements using US in healthy infants during bottle feeding

Bottle feeding

12 babies

Age: 2 to 5 months Mean: 11.5 weeks Range: 8.8–13.5 weeks

C8 convex transducer

Frequency: 5 MHz

B mode

Parameters not specified

The babies were held by one of the parents in a semi-recumbent position on a surface

The transducer was positioned along the midsagittal line of the baby’s body, submental region, without pressure from the oral cavity

The mandible, tongue, submental muscles, nipple, and hyoid bone were visualized. The nipple was visualized as midsagittal as possible

Serve in a bottle, nipple 1, until the best possible recording quality was obtained, the bottle was empty, or the infant stopped drinking

Tongue position during sucking:

Tongue displacement (lifting and lowering) along four evenly distributed lines and anterior and posterior displacements. The contour of the nipple and the tongue surface was referenced to the position of the edge of the mandible

Nipple diameter during compression:

Average difference in diameter (mm) of the nipple during suction. Gray structure presented cylindrically in the image