PROPORTION OF LOW-LYING PLACENTA IN MID-TRIMESTER AND FACTORS ASSOCIATED WITH PLACENTAL MIGRATION: A PROSPECTIVE STUDY AT A TERTIARY CARE CENTRE

Abstract

Background: Low-lying placenta and placenta previa, diagnosed in the mid-trimester, can lead to adverse  maternal and fetal outcomes. Many low-lying placentas detected in the mid-trimester migrate to a normal position by term. This research aimed to identify the prevalence of low-lying placenta during the mid-trimester and assess factors associated with placental migration in the third trimester.

Materials and Methods: In this prospective study, 200 pregnant women attending a tertiary care center underwent routine mid-trimester obstetric ultrasound. Placental location and distance from the internal os were documented. Patients were followed up in the third trimester to assess placental migration. Relevant  clinical data were collected. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS).

Results: The proportion of low-lying placenta in the mid-trimester was 35% (70/200). By the third trimester, the proportion decreased to 14% (28/200), with a 60% migration rate. Factors significantly associated with    placental migration were previous vaginal delivery (85%, p=0.007), placental location (anterior 82.1%, p=0.002), and initial distance from the internal os ≥1.5 cm (83.3%). Factors hindering migration were  previous Lower Segment Cesarean Section (LSCS) (61.5%, p=0.005), history of Medical Termination of Pregnancy (MTP) (76.9%, p=0.003), and initial distance from the os <1 cm (67.8%).

Conclusion: While a significant proportion of pregnancies had low-lying placenta in the mid-trimester, the majority migrated by the third trimester. Factors such as previous vaginal delivery, anterior placental location, and greater initial distance from the os favored placental migration. Conversely, previous LSCS, history of MTP, and shorter initial distance from the os hindered migration.