Objective: To determine whether first-trimester maternal serum levels of pregnancy-associated plasma protein-A (PAPP-A) and free beta-human chorionic gonadotropin (fbeta-hCG) are independent predictors of second-trimester fetal growth parameters.
Methods: This was a cohort study over a 1-year period involving 594 Chinese women who underwent both first-trimester combined screening for Down syndrome and a routine second-trimester ultrasound examination. Maternal PAPP-A and fbeta-hCG levels (expressed in log(10) of multiples of median (MoM)), crown-rump length (CRL) (expressed in standardized Z-score (Z-CRL)), and maternal height and weight, were correlated with the Z-score of biparietal diameter (Z-BPD), femur length (Z-FL) and abdominal circumference (Z-AC) measured in the second trimester, using the Pearson test, followed by multiple regression analysis.
Results: Z-BPD, Z-FL and Z-AC were positively correlated with log(10) PAPP-A MoM, CRL and maternal height (all P < 0.05), while log(10) fbeta-hCG MoM was negatively correlated with Z-AC (P < 0.05). After controlling for the effects of CRL, maternal height and weight, log(10) PAPP-A MoM was found to be an independent positive predictor of Z-FL (r = 0.797, P < 0.001) and Z-AC (r = 0.305, P = 0.049), and log(10) fbeta-hCG MoM was an independent negative predictor of Z-FL (r = -0.381, P = 0.023) and Z-AC (r = -0.418, P = 0.002). Neither hormonal level was related to Z-BPD.
Conclusions: First-trimester PAPP-A and fbeta-hCG are independent factors that influence subsequent fetal growth. PAPP-A level is positively correlated with FL and AC in the second trimester, while fbeta-hCG level is negatively correlated with them. However, BPD is not affected by either of the hormones.
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