Comparison of Placental Location on Ultrasound in Preeclampsia and Normotensive Pregnancy in Third Trimester.

Background: Hypertensive disorders in pregnancy account for 15%-20% maternal and 20%-25% perinatal mortality. There is interest in predicting preeclampsia (PE) early in pregnancy to reduce PE and its subsequent complications. There is no cheap and easily available, reliable predictor for PE. Some studies have shown that the lateral location of placenta is associated with adverse pregnancy outcomes due to PE. The lateral placenta is yet to be proven as a strong predictor of PE to initiate preventive measures. Placental localization can be easily done on routine ultrasonography during pregnancy. In the light of these observations, a prospective study was done to study any association between PE and placental location by ultrasound in third trimester. Research Question: Is there any association between placental location on ultrasound and preeclampsia in third trimester? The objective is to study association between location of placenta and preeclampsia and compare placental location in normotensive pregnancies with that in PE in third trimester.

Methods: A prospective comparative, case-control, observational study was conducted in the Department of Obstetrics and Gynecology at North DMC Medical College and Hindu Rao Hospital, Delhi, India, from August 2019 to April 2020. The study population included 200 pregnant women with singleton pregnancy in third trimester, without any medical disorders such as diabetes mellitus, hypertension, renal disease, cardiac disease, and coagulation disorder or smoking. One hundred women had preeclampsia and 100 were normotensive controls. Ultrasound was done after filling F form as per the Government of India guidelines to rule out sex determination, and placenta was localized by ultrasound. Placenta was classified as central when it was equally distributed between the right and left sides of the uterus irrespective of anterior, posterior, or fundal position and lateral when 75% or more of the placental mass was on one side of the midline. Placental location was compared in hypertensive and normotensive pregnancies.

Results: Out of the total 200 women, 152 (76%) had central and 48 (24%) had lateral placenta. Ninety-two percent of controls and 60% of cases had central placenta. Forty percent of cases and only 8% normotensive women had lateral placenta. Lateral placenta was five times more frequent in presence of PE as compared to normotensive controls. Out of 152 women with central placenta, 92 (60.5%) women were normotensive but with lateral placenta, only 8 (16.7%) had normal blood pressure. PE was present in 83% of women with lateral placenta and in only 39.47% with central placenta. This difference was statistically significant as P < 0.0001 as per Chi-square test. This reflects a significant association between lateral position of placenta and occurrence of PE. As per odds ratio (0.1304) patients without lateral placenta had 90% protection against preeclampsia.

Conclusion: Central placenta is more common than lateral placenta. Lateral placenta is seen five times more frequently among hypertensive women and this difference is statistically significant. The absence of lateral placenta provides 90% protection against PE but the severity of PE was not affected by placental location..