AFP in adverse obstetric outcome
The trophoblast invasion initiates in the first trimester, therefore, attempts are focused on early detection of pregnant women at high risk for subsequent development of those adverse events. Despite the measurements of PAPP-A and AFP at different trimesters of pregnancy, an earlier analysis of AFP would be informative for placental insufficiency . Therefore, the study aims to evaluate the possible association between the maternal serum concentrations of PAPP-A and AFP with the risk of pregnancy adverse outcomes including preeclampsia, fetal growth restriction, and preterm birth. Measurement of AFP and PAPP-A Maternal serum PAPP-A and AFP were measured at the time of first trimester ultrasound examination for aneuploidy screening between 11 and 13+6 weeks. AFP and PAPP-A were measured using chemiluminescence immunoassay method. The concentrations of PAPP-A were expressed as mIU/mL. All biochemical markers were converted to multiples of median (MoM) of the expected normal median for a pregnancy of the same gestational age. PAPP-A and AFP MoM were corrected for maternal weight due to inversely variation in PAPP-A and AFP levels. Low PAPP-A was defined as < 0.41 MoM and high AFP was defined as ≥1.90 MoM according to previous studies [14,15]. The a cut-off value for AFP:PAPP-A ratio was accepted as > 10 . Biochemical markers were converted to multiples of median (MoM) of the expected normal median for a pregnancy of the same gestational age. Receiver Operating Curve (ROC) analysis were performed to identify the cut-off values for diagnosis and assess the diagnostic performance of biochemical markers. Area Under Curve Values (AUCs) were compared to evaluate of diagnostic performance difference between biochemical markers and AFP:PAPP-A ratio.
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Study population This was a prospective observational study recruiting an unselected population of pregnant women attending the maternity care unit of Inonu University, Turgut Ozal Medical Center (between July 2014 to January 2016) for the first trimester screening test for aneuploidy by a combination of fetal nuchal translucency thickness and maternal serum free -hCG and PAPP-A. Blood tests for AFP were also performed at the time of the first trimester screening test. The exact gestational age was estimated from crown-rump length measurement. Maternal age, body mass index (BMI) recorded at the first trimester, smoking status and other clinical characteristics related to pregnancy and birth outcomes were collected by review of electronic databases.