Influence of obesity on first trimester screening markers in singleton pregnant women enrolled at tertiary care hospital

Pregnancy is diagnosed by the detection of beta human Chorionic Gonadotropin (beta hCG) in maternal serum or urine after implantation of the embryo. Primary function of hCG is to maintain the corpus luteum in early weeks of gestation. Pregnancy associated plasma protein A is a glycoprotein exhibits insulin like growth factor binding protein 4 protease activity, which regulates bioavailability of Insulin like Growth Factor-II. Maternal obesity increases the likelihood of serious pregnancy complications both for mother and infant. The altered maternal environment in women with a raised BMI could have adverse consequences for placental development and function thus we hypothesized if maternal body mass index is associated with alterations in serum levels of free β- HCG and PAPP-A After obtaining approval from institutional ethics committee, Kasturba Hospital Manipal, 676 singleton pregnant women of 19-45 years, in 10-14 weeks of gestations were enrolled for the study. Serum free beta hCG and PAPP-A by ECLIA method. BMI was calculated using the formula weight (in kgs)/height in m2. Data were compiled, statistical analysis was done. Non parametric tests were used for analysis. Median and MoM levels of both free beta hCG and PAPP-A showed a significant negative correlation with BMI (p<0.001). To conclude obese women have a larger extracellular volume, larger distribution volume for hCG and PAPPA. Low hCG in women with high BMI may be sequestration of hCG by adipose tissue-resident macrophages. Inverse association of HCG concentration with BMI may be a result of impaired synthesis of HCG in obese women.