Case–control study of prolactin and placental lactogen in SGA pregnancies

Prolactin and placental lactogens increase during pregnancy and are involved with many aspects of maternal metabolic adaptation to pregnancy, likely to impact on fetal growth. The aim of this study was to determine whether maternal plasma prolactin or placental lactogen concentrations at 20 weeks of gestation were associated with later birth of small-for-gestational-age babies (SGA). In a nested case–control study, prolactin and placental lactogen in plasma samples obtained at 20 weeks of gestation were compared between 40 women who gave birth to SGA babies and 40 women with uncomplicated pregnancies and size appropriate-for-gestation-age (AGA) babies. Samples were collected as part of the 'screening of pregnancy endpoints' (SCOPE) prospective cohort study. SGA was defined as birthweight <10th customized birthweight centile (adjusted for maternal weight, height, ethnicity, parity, infant sex, and gestation age) in mothers who remained normotensive. No significant differences were observed in concentrations of prolactin or placental lactogen from women who gave birth to SGA babies compared with women with uncomplicated pregnancies. However, a sex-specific association was observed in SGA pregnancies, whereby lower maternal prolactin concentration at 20 weeks of gestation was observed in SGA pregnancies that were carrying a male fetus (132.0 ± 46.7 ng/mL vs 103.5 ± 38.3 ng/mL, mean ± s.d., P = 0.036 Student’s t-test) compared to control pregnancies carrying a male fetus. Despite the implications of these lactogenic hormones in maternal metabolism, single measurements of either prolactin or placental lactogen at 20 weeks of gestation are unlikely to be useful biomarkers for SGA pregnancies. LAY SUMMARY: Early identification during pregnancy of small for gestational age (SGA) babies would enable interventions to lower risk of complications around birth (perinatal), but current detection rates of these at risk babies is low. Pregnancy hormones, prolactin and placental lactogen, are involved in metabolic changes that are required for the mother to support optimal growth and development of her offspring during pregnancy. The levels of these hormones may provide a measurable indicator (biomarker) to help identify these at risk pregnancies. Levels of these hormones were measured in samples from week 20 of gestation from women who went on to have SGA babies and control pregnancies where babies were born at a size appropriate for gestation age. Despite the implications of prolactin and placental lactogen in maternal metabolism, no significant differences were detected suggesting that single measures of either prolactin or placental lactogen at 20 weeks gestation are unlikely to be useful biomarker to help detect SGA pregnancies.