Characterisation of sucking dynamics of breastfeeding preterm infants: a cross sectional study

Abstract

Background: Full breastfeeding is the ultimate aim for preterm infants to ensure they receive the full benefits of human milk however, preterm infants face a number of challenges associated with their immaturity and associated morbidities. In order to facilitate oral feeding, it is essential to have a sound knowledge of the sucking dynamics of the breastfed infant. The aim of this study was to measure and describe the sucking dynamics of the preterm breastfeeding infant.

Methods: A prospective cross sectional observational study was carried out at King Edward Memorial Hospital, Perth. 38 mothers and their preterm infants (birth gestation age: 23.6-33.3 weeks; corrected gestation age 32.7 to 39.9 weeks) were recruited. Intra-oral vacuum levels, tongue movement and milk intake for a single breastfeed was measured. Statistical analysis employed linear regression and linear mixed effects models.

Results: Synchronised ultrasound and intra-oral vacuum measurements show that the preterm infant generates vacuum by lowering their tongue in a parallel fashion, without distortion of the nipple/nipple shield. Baseline (B), mean (M) and (P) peak suck burst vacuums weakened over the course of a feed (B: p = 0.015; M: p = 0.018; P: p = 0.044) and mean and peak vacuums were weaker if the mother fed with a nipple shield (M: p = 0.012; P: p = 0.021). Infant milk intakes were higher when infants sucked for longer (p = 0.002), sucked for a greater proportion of the feed (p = 0.002), or had a greater sucking efficiency (p < 0.001).

Conclusions: Breastfeeding preterm infants generated intra-oral vacuum in the same manner as term infants. Nipple shields were associated with weaker intra-oral vacuums. However, vacuum strengths were not associated with milk intake rather time spent actively sucking was related to milk volumes. Further research is required to elucidate factors that influence preterm infant milk intake during breastfeeding.

Keywords: Breastfeeding; Infant; Infant feeding; Lactation; Premature; Preterm.

Fig. 1

Ultrasound images of one cycle of a preterm breastfeeding infant feeding with a nipple shield (a) tongue up corresponds with baseline vacuum (b) when the tongue is lowered to the lowest point peak vacuum is applied to the breast and milk flows (c) tongue returns to the soft palate and milk is removed from the oral cavity

Fig. 2

Ultrasound images of one cycle of a preterm breastfeeding infant (a) tongue up corresponds with baseline vacuum (b) when the tongue is lowered to the lowest point peak vacuum is applied to the breast and milk flows (c) tongue returns to the soft palate and milk is removed from the oral cavity

Fig. 3

Nipple diameters plotted at different positions of the nipple (2, 5, 10 and 15 mm) for the breastfeeds with a nipple shield (grey lines; n = 32) and without a shield black lines; n = 6). Continuous lines represent nipple diameter when the tongue is up and dotted lines when the tongue is down

Fig. 4

Average minimum (peak vacuum), mean and average maximum (baseline vacuum) pressures across a feed for infants that were breastfeeding with and without a shield

Fig. 5

Intra-oral vacuum traces of a breastfeed for 2 preterm infants (a) this infant displays peak vacuums between −90 mmHg and – 250 mmHg and is able to maintain suck bursts with more than 10 sucks per burst (b) this infant applies peak vacuum between −10 mmHg and −150 mmHg and often has less than 10 sucks per suck burst and longer pauses than infant (a)