Influence of maternal age and weight on second-trimester serum alpha-fetoprotein, total and free beta human chorionic gonadotropin levels.

BACKGROUND: The purpose of this study was to assess the relation of maternal age and weight on the maternal serum alpha-fetoprotein (AFP), total human chorionic gonadotropin (hCG) and free beta-hCG levels during the second trimester. METHODS: We collected 419 serum samples from normal singleton pregnancies to assay serum marker levels of AFP, total hCG and free beta-hCG between 14 and 21 weeks of gestation. Maternal age at the day of delivery and maternal weight at the time of sampling were recorded in all cases. The relationship between maternal weight and multiple of the median (MoM) levels of serum markers was analysed by regression models. RESULTS: There was an inverse trend in median MoM levels of serum markers in relation to maternal weight. No significant association between maternal age and serum marker levels was found. CONCLUSION: Because of its impact on serum marker levels, weight correction may be mandatory for further refinement in the maternal serum screening for Down's syndrome.