Investigating the Relationship between Serum Levels of PAPP-A and Free β-hCG in the First Trimester of Pregnancy with Placental Thickness and Percentile of Fetal Weight in Third Trimester Ultrasound

Abstract

Introduction: Fetal growth disorder is one of the most important factors in the morbidity and mortality of newborns. Investigating the factors and predicting them can be done through biochemical markers and sonography. The quality of the placenta was measured by measuring PAPP_A and free B_HCG and its quantity by examining the placenta by ultrasound. This study aimed to determine the correlation between fetal growth percentile and these three variables. Methods: This prospective cohort study was conducted on 462 pregnant mothers in Ahvaz. The criteria of this study were singleton pregnancies, accurate knowledge of last menstrual date, non-smoking, no drug or alcohol consumption and consent to participate in the research exclusion criteria were fetal anomaly, chromosomal disorder and lack of ultrasound in the third trimester. PAPP-A and free B-HCG were measured in the 11–13 + 6 weeks of pregnancy, and then in the third trimester fetal placental thickness and fetal weight were measured by two-dimensional sonography. The data was analyzed using SPSS software version 26 as well as Pearson statistical logistic test and the results were analyzed. Results: Out of the 462 fetuses none of them were under the 10% weight percentile. 187 fetuses were between 10%–50% of the weight percentile and 260 fetuses were between 50%–90% weight percentile and 15 fetuses were above the 90% weight percentile. The level of free B-HCG was significantly different in the three weight groups, the uppermost level of B-HCG was in the 90% weight percentile group (p-value = 0.008). The level of PAPP-A also correlated with the fetuses’ weight percentiles (p-value = 0.002). There was a positive and significant correlation between placental thickness in the third trimester in the three groups (p-value = 0.004) which means that with the increase in the thickness of the placenta, the fetus’s weight increases. Conclusion: Based on this study, the measurement of placental markers and diameter helps predict birth weight and is expected to help in deciding the time and type of pregnancy termination.