Placenta previa is a condition where the placenta is attached over the cervix. This is fairly common early in pregnancy but usually goes away so that it becomes uncommon near term. Pelvic rest, (nothing in the vagina), is very important with placenta previa. If there is a placenta previa at term, a c-section will be needed.
The placenta is basically a bag of blood vessels. It is where the blood from the baby and the blood from the mom interact to pass oxygen and nutrients to the baby. When the placenta first implants, it can attach anywhere in the uterus. As the uterus grows, the placenta will preferentially grow towards the top of the uterus because that is where the richest blood supply is. The cervix is the opening of the uterus to the vagina. If the placenta is over the cervix, there is potential for it to be damaged by being struck through the vagina. This is why with a placenta previa Pelvic rest is important.
Pelvic rest means nothing inside the vagina. No sex, no tampons, no doctor’s fingers, nothing. Anything that can hit the cervix has the potential of injuring the placenta when a placenta previa is present. This can lead to bleeding and potentially significant or even catastrophic bleeding. The other way that placenta previas can bleed is with contractions such as in preterm labor. Apart from these two scenarios, it is unusual to see significant bleeding with a placenta previa. All women with placenta previa need to be on pelvic rest. The need for bed rest is more controversial and depends on the individual situation. If activity is causing contractions, then bed rest is probably indicated. Women with placenta previa who have bleeding are typically placed on bed rest as well.
Placenta previa can be described as complete (completely over the cervix), partial (only partially over the cervix), marginal (just next to the cervix), or low lying (close to the cervix). The less it is over the cervix, the better the chance that it will move away over time. It is when the placenta is completely covering the cervix and doing it fairly symmetrically that it will not resolve with time.
If a placenta previa remains present at term, a c-section must be performed. This is because the placenta will be blocking the cervix and the baby can not come out vaginally without tearing through the placenta. This would cause massive hemorrhage. C-sections with placenta previa are very safe and usually very routine.
In the case of placenta previa at term in a woman with a previous c-section, a placenta accreta is possible. Placenta accreta is a condition in which the placenta grows into the muscle layer of the uterus. This can be very dangerous as the placenta may not detach. If this is present, a cesarean hysterectomy (removal of the uterus at the time of c-section) may be necessary. Fortunately, these are extremely rare.
Overall, a diagnosis of placenta previa can be safely managed as you wait for the previa to resolve. In cases where the previa does not resolve, then a c-section can make delivery safe for both you and the baby. Pelvic rest and sometimes bed rest are the treatment for placenta previa.