Rajib Pal1, Basab Bijay Naskar2, Tapan Ganguly3, Rajugopal Saha4, Mrinal Kanti Ghosh5, Prabir Sengupta6
BACKGROUND
We wanted to determine the incidence of a low-lying placenta diagnosed on
routine ultrasonography in second trimester and those diagnosed as placenta
previa in the third trimester. We also wanted to evaluate the factors affecting such
migration and evaluate the fetomaternal outcome.
METHODS
In this prospective study all cases of low-lying placenta detected on routine
ultrasound scan in second trimester were followed up with serial sonography
evaluating placental migration in third trimester and also in those whose placentas
never cleared of internal os and persisted as placenta previa. The study included
a total 200 antenatal primigravida mothers without any risk factors and was
conducted over a period of one year.
RESULTS
Out of 200 mothers, 13 patients had no further follow-up, sonographic
examinations or obstetric care in our institution leaving 187 patients. Among 187
women, placental migration occurred in 175 women and 12 had placenta previa.
Anterior low lying placentas were more common and most of them migrated from
internal os between 28w - 31w 9d of gestation. A small number of placentas
cleared after 36 weeks but before delivery. Anterior placenta previa were more
common than posterior ones. Diagnosis of low lying placenta occurred at 18w -
18w 9d of gestation. Among low lying placenta in mid trimester whose initial
distance from internal cervical os was < 10 mm are not migrated, and end in
placenta previa. Maternal complications like antepartum haemorrhage,
postpartum haemorrhage were more common in low lying placenta. Fetal
complications include intrauterine growth restriction (IUGR), preterm birth and
neonatal complications like low Apgar score at birth, and sick newborn care unit
(SNCU) admissions were more common in placenta previa compared to normal
location of placenta.
CONCLUSIONS
A low lying placenta diagnosed by ultrasonography in second trimester resolves
by mid of third trimester. Only rarely 6.4 % persist to term or near term. Follow
up sonography is required to diagnose persistence of placenta previa.
