Sima Fallah Arzpeyma - Assistant Professor of Radiology, Department of Radiology, Poursina Hospital, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran.
Zohre Asadi - Resident of Radiology, Reproductive Health Research Center, Student Research Committee, Guilan University of Medical Sciences, Rasht, Iran.
Sodaboeh Kazemi - Assistant Professor of Obstetrics and Gynecology, Reproductive Health Research Center, Department of Obstetrics & Gynecology, Al-Zahra Hospital, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran.
Ehsan Kazemnejad-Leili - Associate Professor, Department of Biostatistics, Social Determinants of Health Research Center, Guilan University of Medical Sciences, Rasht, Iran.

Background: The low level of pregnancy-associated plasma protein A (PAPP-A) has a relationship with unfavorable outcomes in neonates. This study aimed to evaluate the association between the thickness and size of the placenta in singleton pregnant women. Materials and Methods: In this prospective cohort study, ۱۰۲ women were investigated in ۱۸-۲۳ weeks and PAPP-A level at the gestational age in ۱۱-۱۴ weeks with a singleton pregnancy who referred to Al-Zahra Hospital, Rasht, Iran, between ۲۰۱۷ and ۲۰۱۸. Serum PAPP-A of pregnant women was measured in the first trimester of pregnancy. Patients who had PAPP-A ≤ ۰.۵ Multiple of the Median (MOM (were dedicated to an exposed group and others to a non-exposed group. Placental thickness and size were assessed during the second trimester by ultrasound examination and described as abnormal high thickness if the thickness was > ۴ cm or more than ۵۰% of the placental length and abnormally small size when the maximum length was < ۱۰ cm. Then, placental thickness and size were compared between the two groups. Results: PAPP-A levels of > ۰.۵ and ≤ ۰.۵ were recorded in ۶۰ and ۳۴ patients, respectively. Women with low levels of PAPP-A in the first trimester had an increased incidence of abnormal placental thickness in ۱۳ cases and small placental size in ۷ cases, whereas this number was ۱۲ and ۷ cases, respectively, in the other group (P = ۰.۰۲۳). The sensitivity and specificity of PAPP-A < ۰.۵۵ were ۷۲.۳ and ۵۶% for abnormal placental thickness, respectively; the sensitivity and specificity of PAPP-A < ۰.۵۵ were ۶۹.۳ and ۵۷.۱%, respectively, in the assessment of abnormal placenta size. Conclusion Based on the results, the size and thicknesses of the placenta were abnormal in women with a low level of PAPP-A (≤ ۰.۵).

PAPP-A, pregnancy, Placenta, Women