The perception of an inadequate milk supply can contribute to a new mother’s decision to cease breastfeeding prematurely, but identifying at-risk women is difficult. Now a new study suggests that, for some women, this impression, known as perceived inadequacy of milk supply (PIMS) appears to have a basis in genetics.
Steven D. Hicks, MD, PhD, associate professor of pediatrics at Penn State University, Hershey, and colleagues found that variations in the MFGE8 gene was associated with perceived breast milk supply.
Dr. Steven D. Hicks
“Genotyping one lactogenic gene aided identification of mothers at risk for PIMS. If validated in a larger cohort, such an approach could be used to identify mothers who may benefit from increased lactation support.” Dr. Hicks’ group wrote in Breastfeeding Medicine.
A simple 24-hour polymerase chain reaction test around the time of delivery could identify vulnerable mothers, who could receive targeted lactation support including galactagogue supplementation and early scheduling of “nurse and pump” routines.
“Also, if a woman is found to have PIMS, she would definitely want to avoid going on oral contraceptives after delivery as these can affect milk supply,” Dr. Hicks said in an interview. “That would be like a double hit in a woman already at risk.“
In other measures, she would meet once a week with a lactation consultant for the first 6 months to make sure good breastfeeding practices as to frequency and duration of placing the baby on the breast are being maintained, Dr. Hicks continued. “She needs to make sure her supply isn’t going backwards because once it starts to dry up, it’s really hard to turn the ship around.”
Dietary interventions to promote lactation may also help.
The study
In the context of a larger study on breast milk factors protecting children from developing allergies, the prospective observational analysis collected data on 221 breastfeeding mothers aged 19-42 years (mean age, 29 years) for 12 months.
All mothers had initially planned to nurse their babies for at least 6 months but some stopped well short of their goal.
“At least a third told us they gave up because they felt their milk supply had run out,” Dr. Hicks said in an interview.
Using salivas swabs, the investigators assessed 18 genes secreted from mammary tissue and previously linked in cows to secretory function for single-nucleotide polymorphisms in 88 age-, race-, and parity-matched women. Of these, 45 had PIMS and 43 had perceived adequate milk supply (PAMS).
Among differences between the two groups:
- PIMS mothers breastfed exclusively for a shorter period than PAMS mothers: 7 ± 12 weeks versus 22 ± 19 weeks(P = .001)
- At 1 month after delivery, their reported milk production was lower: 17.6 ± 13.3 oz/day versus 27.0 ± 12.2 oz/day (P = .0001). This shortfall persisted at 4 months: 16.0 ± 14.1 oz/day versus 27.3 ± 14.9 oz/day (P < .0010.
- Between birth and 1 month, infants of PIMS mothers also showed a smaller average increase in weight-for-length z score between birth and 1 month: 0.74 ± 1.4 versus 1.4 ± 1.5 (P = .038).
Furthermore, maternal genotype for the rs2271714 variant within MFGE8 was associated with PIMS status (P = .009; adjusted P = .09; likelihood ratio, 9.33), and duration of exclusive breastfeeding (P = .009; adjusted P = .09; chi square, 9.39).
Adding the MFGE8 genotype to a model including maternal age, parity, previous breastfeeding duration, body mass index, education, and depression status significantly increased predictive accuracy for PIMS status, the authors noted.
Dr. Shannon L. Kelleher
“This is a very exciting observation made by Dr. Hicks and his team, and the first study to identify a genetic variant associated with perceived insufficient milk supply,” said Shannon L. Kelleher, PhD, professor of biological and nutritional sciences at University of Massachusetts, Lowell.
“It provides compelling evidence that insufficient milk supply is very common and supports the urgent need to identify the risk factors and develop interventions to improve breastfeeding success,” added Dr. Kelleher, who was not involved in the study.
“If genetic variants such as the one identified in MFGE8 are confirmed to be common in mothers with insufficient milk supply, the development of lactation-focused genetic tests to identify women at risk for low milk supply would revolutionize our ability to support breastfeeding mothers and help them achieve their breastfeeding goals.”
Although 83% of new mothers initiate breastfeeding, only 57% are still breastfeeding at 6 months and only 35% breastfeed until 12 months, according to the Centers for Disease Control and Prevention’s Breastfeeding Report Card.
This study was funded by grants to Dr. Hicks from the Gerber Foundation and the Center for Research on Women and Newborns Foundation. The authors disclosed no competing interests. Dr. Kelleher reported no conflicts of interest relevant to her comments.