Abstract
Background: Placenta previa, where the placenta implants over the internal cervical os, risks antepartum hemorrhage and perinatal mortality. Placental migration away from the os often occurs as the lower uterine segment elongates in advancing gestation. However, resolution patterns in low-risk primigravid women under 35 with an anteverted uterus remain poorly characterized in the literature. Objective: To assess the sonographic resolution of placenta previa from the 2nd to the 3rd trimester in primigravid women with an anteverted uterus and non-advanced maternal age (<35 years), and to determine the predictive value of the 2nd trimester placenta-to-internal os distance (IOD) for resolution.
Methods: A 4-month prospective study at Sheikh Zayed Hospital and private centers in Rahim Yar Khan enrolled 167 primigravid women (18–34 years, singleton, anteverted uterus) with 2nd-trimester placental edge ≤20 mm from internal os. Transabdominal ultrasound (3–5 MHz) measured placenta-to-internal os distance (IOD) in both trimesters. Data were analyzed using descriptive statistics, Mann-Whitney U, Pearson correlation, and Chi-square tests.
Results: Of 167 patients (mean age 27.6 ± 3.0 years, mean 2nd-trimester IOD 11.6 ± 6.0 mm), placenta previa resolved by the 3rd trimester in 94 (61.0%). Resolution varied by previa type: low-lying 94.9%, marginal 65.4%, partial 23.5%, complete 0.0% (p<0.001). Mean IOD was higher in resolved (14.9 mm) vs. unresolved (4.8 mm) groups (p<0.001). A strong positive correlation existed between 2nd- and 3rd-trimester IOD (r=0.858, p<0.001). Younger women (<25 years) had higher resolution rates (88.0%) than those aged 30–34 years (29.3%). Placental position did not significantly influence resolution (p=0.780). Conclusion: The majority of placenta previa cases in primigravid women with an anteverted uterus resolve spontaneously by the 3rd trimester. The 2nd trimester IOD is a strong, statistically significant predictor of resolution. Complete previa and low initial IOD values are associated with persistent placenta previa requiring planned cesarean section. These findings support individualized obstetric counseling based on sonographic parameters in this specific low-risk cohort