(P07-025-23) Maternal Plasma Amino Acid Concentrations Throughout Pregnancy and Neonatal Anthropometrics Measures: Friends or Foes of Fetal Growth?

Objectives: Maternal amino acids (AA) are crucial for fetal growth. Although AA levels change across pregnancy, previous studies assessed maternal AA levels with a one-point-in-time measurement. Our aim was to study the associations between longitudinal maternal plasma AA levels across pregnancy and fetal growth proxies, including birthweight z-score, birth length, and sum of skinfolds.

Methods: Concentrations of 24 plasma AAs were assessed at 10–14, 15–26, 23–31 and 33–39 gestational weeks (GW) among 321 women from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Fetal Growth Studies-Singletons. At each time point, associations between the individual maternal AA, considered as tertiles, and fetal growth were assessed using weighted generalized linear models adjusted for maternal age, education, parity, gestational age at blood collection, pre-pregnancy BMI and infant sex.

Results: Women with a greater glutamine level at 10–14 GW had offspring with higher birthweight z-score and greater length (tertile 3 vs 1: adjusted β [95% CI]: 0.31 [0.06, 0.56], P-trend = 0.04 and 1.35 cm [0.32, 2.37], P-trend = 0.04, respectively). By contrast, a greater aspartic acid level at 23–31 GW was associated with lower birthweight z-score, smaller length and sum of skinfolds (tertile 3 vs 1: -0.35 [-0.70, -0.00], -1.3 cm [-2.4, -0.15], and -3.9 mm [-6.0, -1.7], P-trend = 0.007, respectively). Moreover, women with greater glycine levels at 10–14 and 33–39 GW had offspring with lower birthweight z-score (tertile 3 vs 1: -0.37 [-0.65, -0.08], P-trend = 0.04 and -0.38 [-0.75, -0.02], respectively). Greater glycine levels at 23–31 and 33–39 GW were also significantly associated with lower length and sum of skinfolds. Women with greater methionine levels at 10–14 and 15–26 GW had offspring with shorter length (tertile 3 vs 1: -0.90 cm [-1.73, -0.06] and -1.4 cm [-2.4, -0.41], P-trend = 0.01, respectively).

Conclusions: This study suggests maternal AA levels starting in early pregnancy are associated with neonatal anthropometrics, with the associations varying by types of AA and time point. Given the potential modifiability of AAs by diet, AAs may represent a target to prevent sub-optimal fetal growth.

Funding Sources: National Institute of Child Health and Human Development intramural funding