Prolactin in high-metabolic risk pregnancies: Associations with maternal obesity and metabolic health

Low prolactin levels during pregnancy have been linked to adverse maternal metabolic health. We examined pregnancy prolactin levels in relation to maternal metabolic characteristics within an ethnically diverse cohort at high metabolic risk.

In this observational cohort study, pregnant women (n = 130) with metabolic risk factors were characterized in early pregnancy, with sampling of serum prolactin and metabolic parameters. Fifty-four women with gestational diabetes consented to serial profiling across pregnancy. Univariable and multivariable simple and mixed-effects regression models examined relationships between prolactin and maternal variables.

Women with obesity (BMI ≥30 kg/m²) had lower early pregnancy prolactin levels than women without obesity (35.1 vs 44.3 μg/L, p = 0.03). Lower prolactin in early pregnancy was associated with higher parity and higher early pregnancy BMI, fasting insulin, insulin resistance, and diastolic blood pressure, but only relationships with parity and BMI persisted after adjustment for covariates. In the serially sampled cohort, lower prolactin levels across pregnancy were independently associated with higher pre-pregnancy maternal BMI (adjusted β = -3.25, p = 0.04). Lower absolute prolactin increment from early to late pregnancy was independently associated with higher pre-pregnancy and early pregnancy maternal BMI (p = 0.046 and p = 0.04, respectively).

Maternal metabolic status, particularly higher BMI before and during early pregnancy, was associated with lower prolactin levels in early pregnancy and across gestation, and a smaller prolactin increase over pregnancy. Lower prolactin levels may reflect underlying metabolic health and may be relevant to the suboptimal lactation outcomes observed in women with obesity and metabolic disease.