Does a Baby Born at 37 Weeks Contribute to Inhibited Letdown?
A baby born at 37 weeks (early term) does not directly cause inhibited milk letdown, but the combination of infant immaturity and maternal delayed lactogenesis creates significant breastfeeding challenges that can manifest as poor milk transfer and perceived low supply.
Understanding the Mechanism
The issue is not that 37-week infants cause inhibited letdown, but rather that they face a constellation of feeding difficulties that overlap with letdown problems:
Infant-Related Factors at 37 Weeks
Early term infants (37-38 weeks) have decreased breastfeeding rates compared to full-term newborns, primarily due to infant immaturity, decreased effective milk emptying, and maternal delayed onset of lactation 1.
These infants demonstrate decreased effective milk emptying, which fails to adequately stimulate the breast and can lead to a cycle of poor supply and inadequate letdown 1.
Inadequate human milk intake in the first days after delivery contributes to longer hospital stays and higher rates of hospital readmissions in this population 1.
The Late Preterm Context (34-36 Weeks)
While your question asks about 37 weeks specifically, the research on late preterm infants (34-36 weeks) provides critical context, as these infants face even more pronounced versions of the same challenges:
Mothers of late preterm infants commonly experience challenges with latching and milk supply, with many reporting negative experiences of milk supply concerns 2.
In a study of breastfeeding problems, inhibited letdown was present in 19.5% of cases and was associated with the poorest breastfeeding outcomes compared to forceful or average letdown 3.
Common difficulties in late preterm infants include delayed lactogenesis, decreased milk transfer, and ineffective suck and swallow, which often lead to premature breastfeeding cessation 4.
Clinical Approach to Management
Immediate Assessment Priorities
Evaluate the mother-infant dyad for effective milk transfer by observing feeding sessions and assessing infant weight gain patterns 4.
Assess maternal milk letdown by manual expression to determine if letdown is inhibited, average, or forceful 3.
Monitor for signs of inadequate intake: dehydration, excessive weight loss (>7% of birth weight), and hyperbilirubinemia 1, 4.
Intervention Strategy
For mothers with adequate or forceful letdown but poor infant transfer:
Implement nipple shields and other devices to assist with latching 2.
Use hand expression or supplementation with small volumes of expressed maternal milk or donor milk to limit the burden of pumping while maintaining supply 2.
Increase feeding frequency to 9-10 times daily, as this is associated with better outcomes and lower bilirubin concentrations 1.
For mothers with true inhibited letdown:
Recognize that inhibited letdown has significantly poorer breastfeeding outcomes (p=0.57 for continued breastfeeding vs. p=0.0001 for forceful letdown) 3.
Provide intensive lactation support focusing on relaxation techniques, skin-to-skin contact, and addressing maternal stress or pain that may inhibit oxytocin release.
Consider galactagogues and pumping protocols to establish supply while working on letdown issues.
Critical Follow-Up
Establish close outpatient follow-up within 24-48 hours of discharge to assess weight gain, jaundice, and feeding effectiveness 4.
Provide comprehensive lactation support after hospital discharge, as mothers report inadequate support during this critical period 2.
Common Pitfalls to Avoid
Do not assume that "perceived low milk supply" equals true low supply — in one study, 19 of 37 mothers with acceptable letdown presented with perceived low supply, and only 3 remained unconvinced after proper assessment 3.
Avoid routine formula supplementation without clear medical indication, as formula supplementation is associated with increased exclusive formula feeding at discharge 1.
Do not dismiss maternal concerns — mothers of late preterm and early term infants report feelings of guilt and failure when breastfeeding challenges arise 2.
Avoid pacifier use and bottle feeding in the early weeks, as these are associated with breastfeeding rejection 3.
The Bottom Line
A 37-week infant does not directly inhibit maternal letdown, but the infant's relative immaturity creates a bidirectional problem: the infant cannot effectively empty the breast, which fails to adequately stimulate milk production and letdown, leading to a cycle of perceived and sometimes actual low supply. The key is early, intensive lactation support with frequent assessment of the mother-infant dyad and individualized interventions targeting both milk production and infant feeding effectiveness 4, 5.