The prospective associations of fetal growth-related pregnancy complications with subsequent breastfeeding duration and markers of human milk production.

Abstract

The development of the breast for lactation occurs throughout pregnancy. It is unknown whether pregnancy complications resulting in poor fetal growth can affect breastfeeding success. We examined whether fetal growth-related pregnancy complications were associated with earlier breastfeeding cessation and changes in the concentrations of human milk biomarkers of low milk production. We used data from the Growing Up in Singapore Toward healthy Outcomes (GUSTO) study (n=954). Human milk concentrations of protein, lactose, citrate, sodium, potassium and zinc at 3 weeks postpartum were available for 180 mother-infant dyads. We examined the associations of fetal growth measures, including term infants born small-for-gestational-age (SGA) (<10th percentile), pregnancies complicated by fetal growth deceleration (FGD) (2nd - 3rd trimester fetal growth dropped between major centiles), elevated umbilical artery resistance (UAR) (> 90th percentile) or hypertensive disorders of pregnancy (HDP) with (i) risk of ceasing breastfeeding (Cox regression) and (ii) concentrations of human milk components (weighted linear regression). Adjusting for maternal education, smoking exposure, breastfeeding intentions and pre-pregnancy BMI, individuals who delivered SGA infants, and those with HDP were more likely to breastfeed for a shorter duration when compared to those with uncomplicated pregnancies (adjusted hazard ratio [95% CI]: 1.45 [1.11, 1.89] and 1.61 [1.14, 2.29], respectively); associations were not significant for FGD and UAR. SGA was not associated with concentrations of human milk biomarkers, but compared to participants with uncomplicated pregnancies, milk produced by those with HDP contained lower zinc concentrations (adjusted beta coefficient [95% CI]: -0.56 mg/L [-1.08, -0.04]). Individuals with HDP and those with SGA infants tend to breastfeed for a shorter duration; however, only HDP appeared to be associated with biomarkers of compromised milk production. Further research and support are needed to help individuals with HDP and SGA achieve their breastfeeding goals. This study was registered as NCT01174875, and can be accessed at https://clinicaltrials.gov/study/NCT01174875.