A complete placenta previa is a serious condition where the placenta covers the cervix. In this instance, the only way to deliver the infant is by cesarean section. The head cannot enter the birth canal because of the placenta, and even more concerning is the fact that the placenta will start bleeding heavily once the labor ensues and the cervix starts to dilate. Therefore, the cesarean section will be performed prior to the onset of labor at about 38 weeks gestation as long as heavy vaginal bleeding does not complicate the clinical picture. If recurrent vaginal bleeding or heavy vaginal bleeding complicates the pregnancy, your provider may treat you with intramuscular betamethasone in order to accelerate fetal lung maturity as the infant may have to be delivered sooner than 38 weeks. The betamethasone can be given as early as 24-26 weeks gestation.
There is also a partial placenta previa where the placenta covers part of the cervix. This condition will again entail an automatic cesarean section prior to the onset of labor as in the case of the complete placenta previa.
The third type of placenta previa is the marginal placenta previa. In this situation, the placental edge borders the cervix. It is possible to deliver vaginally in this case, but there is still the possibility of heavy bleeding once the cervix dilates. For this reason, your provider will have an operating room ready in case you start to bleed heavily. Your provider will discuss the pros and cons of allowing labor to begin in the case of the marginal placenta previa and you can decide whether you want to try to deliver vaginally or not. This is the one type of placenta previa, however, which does not automatically mean a cesarean section.
A placenta previa will often present with painless vaginal bleeding. Sometimes, the bleeding will be life threatening, and other times, the vaginal bleeding will be more like spotting. Your provider will get an ultrasound in this case (if he hasn’t already), and the placenta previa will then be diagnosed. At that time, your provider will know if the placenta is a complete, partial, or marginal previa.
Once a diagnosis of a previa is made, your provider will ask you to follow a regimen of bedrest. This means avoiding heavy lifting, prolonged walking, and exercise in general. Your provider will also ask you to avoid sexual intercourse, and he will also recommend avoiding pelvic exams as any of these acts can provoke vaginal bleeding. A placenta previa is a potentially life threatening condition so it is important that you follow your provider’s recommendations.
The incidence of placenta previa is about 1 out of 200 pregnancies. Certain factors will predispose you to a placenta previa although the exact reason for a previa is unknown. Having had more than one pregnancy prior to the present pregnancy, maternal age older than 35 years, being pregnant with twins or more, smoking, having had a previous previa, or having had previous uterine surgery are all risk factors for a previa.
As I mentioned previously, the diagnosis is made by either a routine ultrasound or an ultrasound performed due to vaginal bleeding. There is often a diagnosis of placenta previa made on a routine first trimester ultrasound. The important thing to remember is that this type of previa will usually resolve as the pregnancy progresses and the uterus enlarges. So don’t panic if you have a first trimester diagnosis of placenta previa as the condition will most likely resolve. Your provider, however, will follow the resolution of the previa with serial ultrasounds to make sure that you and your baby are not in danger. The late second trimester and third trimester placenta previas are the ones to worry about.
If you are Rh negative, and the father of the baby is Rh positive, then you should be treated with Rhogam each time that you have a bleeding episode in order to avoid maternal Rh sensitization which can lead to fetal complications in future pregnancies.
Wishing you a safe and problem free delivery, Pablo.