Weight of Pregnant Women and their Influence on Second Trimester Biochemical Markers

Fetal aneuploidies screening was based for a long time on ultrasonographic and biochemical markers measurement. The risk calculated in accordance with second trimester biochemical markers (STBM) values relies on calculation of corrected MoM values. MoM (multiple of Medians) signify the deviation of a measured value from the expected value (Median). The Median is measured at the same gestational age in pregnancies which involve healthy fetuses. The correction of MoM includes an adjustment for certain parameters that influence the STBM value: demographical (ethnicity), behavioral (smoking status, weight), and others (mode of conceiving, etc.). In our article we aim to analyze: (1) the accuracy of software to calculate STBM corrected MoM values, (2) the effect of weight of pregnant women on STBM and (3) the capability of software to counterbalance this influence. Pregnant women (n=1242) were screened for aneuploidies based on an integrated test: first trimester ultrasound and STBM (AFP, hCG and uE3). The absolute value, multiple of median (MoM) and corrected multiple of median (MoMc) values were 33.94 +/- 0.45, 1.04 +/- 0.12 and 0.98 +/- 0.01 for AFP, 22530 +/- 477, 0.87 +/- 0.01 and 0.85 +/- 0.01 for hCG, respectively 0.97 +/- 0.03, 0.99 +/- 0.01 and 0.98 +/- 0.01 for uE3. The weight of pregnant women inversely correlates with absolute and MoM AFP, hCG and uE3 values. No correlation was found with AFP and hCG MoMc values. A very weak inverse correlation was found between weight and uE3 corrected MoM values. Our study confirms that there is a difference between provider and own calculated hCG MoMc values. The weight of pregnant women inversely correlates with STBM values. The software used for aneuploidies risk evaluation corrects the influence of weight of pregnant women, but a minimal influence on uE3 corrected MoM values is still present.