Placenta praevia is an abnormal condition during pregnancy in which the placenta blocks the cervical opening and thus hinders the birth passage of the baby. The placenta may be low lying in some women and may partially or totally cover the cervical opening. When the cervical opening is fully covered, it is called total placenta praevia and when partially blocked, it is called partial placenta praevia.
Low lying placenta is common during early pregnancy when the uterus is not enlarged enough. At this time, the placenta may partially overlie the cervix. However, by later pregnancy, the placenta usually occupies its normal position and leaves the cervical opening unhindered. One in about 200 pregnancies manifests a case of placenta praevia.
What are the causes?
The most common cause of placenta praevia is an abnormality in the uterine wall or the abnormal formation of the placenta itself. The placenta may be too large to fit comfortably in the uterus and thus may lie lower than usual. The risk for placenta praevia increases with each pregnancy. Also mother of closely spaced children may be at an increased risk. Pregnant women carrying multiple babies are also at an increased risk.
Other risk factors for the condition include previous removal of uterine fibroids, a prior caesarean section and number of previous successful deliveries.
What are the symptoms?
Placenta praevia is manifested around the third trimester of pregnancy, usually after the 28th week. It is marked by profuse vaginal bleeding which is sudden and painless. Some cramping and heaviness of the uterus may occur which may also prepone labour.
How is it diagnosed?
Bleeding in the third trimester warrants a thorough abdominal check up. An ultrasound shows the fetal position to be oblong or horizontal. The placental positioning is also usually evident from the ultrasound.
What is the treatment?
Pregnant mothers with placenta praevia are advised immediate and complete bed rest depending upon the amount of bleeding. Hospitalisation may be required in cases of extreme bleeding and resulting weakness. Medication may be given to the mother to prevent premature labour and to extend the pregnancy to atleast 36 weeks. Caesarean is the preferred method of delivery in such cases to minimise the risk for the mother and the baby.
What are the complications?
There may be complications for the mother which include haemorrhage, blood loss leading to shock, and in some cases, death. There may be an increased risk of infections or blood clots. There may be harm to the baby also as adequate nutrition may not be available due to placental abnormality. The baby may be born prematurely and may suffer haemorrhage.