Placenta previa occurs in about 1 in 200 pregnancies at term. The condition is one where the placenta attaches itself to the lower part of the uterus wall covering the cervical opening to some extent. It is more common in the early months of pregnancy. Placenta previa poses a risk to the mother and her unborn child because of the potential danger associated with excessive bleeding should it occur during pregnancy or delivery. Another variation to placental abnormality is the low-lying placenta, where the placenta is very close to the cervical opening but doesn't quite reach it.
Placenta previa is uncommon in a first pregnancy but the tendency increases with additional gestations. The three placenta previa types are total placenta previa, partial placenta previa and marginal placenta previa, with marginal being the most common of the three. A routine ultrasound performed in weeks 18-20 allows the diagnosis of previa. In other instances diagnosis is made when the pregnant mother experiences 2nd trimester bleeding. A reevaluation through ultrasound will be typically performed between weeks 30-36. In a large number of cases the placenta will move out of the way before week 30 when the pregnancy progresses and the uterus would have expanded and stretched.
What Causes Placenta Previa
Once again the cause is not known but the risk increases in the following situations:
- Placenta previa in an earlier pregnancy
- If you had previous c-section(s)
- In multiple pregnancy
- In older women
- In women who smoke
- If uterine surgeries were performed e.g. D&C or fibroids removal
- Any bleeding in the second half of pregnancy warrants medical attention. Painless vaginal bleeding which is sudden near the end of the 2nd trimester or the beginning of the 3rd is indicative of placenta previa. Ultrasounds are effective in detecting this problem. Vaginal probe is never performed as it may cause a disruption and result in severe bleeding.
- Bleeding in late pregnancy suggests pre-labor contractions are dislodging the roots of the placenta. This threatens baby's nourishment and oxygen supply if labor were allowed to proceed. The added stress is that the placenta will hinder baby's way out through the birth canal. Cesarean becomes necessary to save the baby.
- Cesarean becomes inevitable in cases with total previa. With marginal or partial previa vaginal birth is still possible. A vaginal or cesarean delivery will depend on how much the cervix is covered.
- A woman with any kind of previa should not put anything into her vagina including douches or medications. Sexual intercourse should be avoided. Bed rest is advised to decrease pressure at the placental site. All kinds of strenuous activities should be avoided and that includes heavy jobs and carrying heavy articles.
- If after week 36 the placenta is found to be lying low but not covering the cervix and there is no bleeding, the mother has the option of staying at home but extra visits to the doctor is necessary. Most doctors would prefer the 'wait and see approach' so that baby matures up while still in the utero. Others would prefer to induce labor early. Either way you have to take things easy.