What is placenta previa?
If you have placenta previa, it means that your placenta is lying unusually low in your uterus, next to or covering your cervix. The placenta is the pancake-shaped organ — normally located near the top of the uterus — that supplies your baby with nutrients through the umbilical cord.Placenta previa is not usually a problem early in pregnancy. But if it persists into later pregnancy, it can cause bleeding, which may require you to deliver early and can lead to other complications. If you have placenta previa when it's time to deliver your baby, you'll need to have a c-section.If the placenta covers the cervix completely, it's called a complete or total previa. If it's right on the border of the cervix, it's called a marginal previa. (You may also hear the term "partial previa," which refers to a placenta that covers part of the cervical opening once the cervix starts to dilate.) If the edge of the placenta is within 2 centimeters of the cervix but not bordering it, it's called a low-lying placenta. The location of your placenta will be checked during your midpregnancy ultrasound exam.
What happens if I'm diagnosed with placenta previa?
It depends on how far along you are in pregnancy. Don't panic if your second trimester ultrasound shows that you have placenta previa. As your pregnancy progresses, your placenta is likely to "migrate" farther from your cervix and no longer be a problem. (Since the placenta is implanted in the uterus, it doesn't actually move, but it can end up farther from your cervix as your uterus expands. Also, as the placenta itself grows, it's likely to grow toward the richer blood supply in the upper part of the uterus.)Only about 10 percent of women who have placenta previa noted on ultrasound at midpregnancy still have it when they deliver their baby. A placenta that completely covers the cervix is more likely to stay that way than one that's bordering it (marginal) or nearby (low-lying).Even if previa is discovered later in pregnancy, the placenta may still move away from the cervix (although the later it's found, the less likely this is to happen). You'll have a follow-up ultrasound early in your third trimester to check on the location of your placenta. If you have any vaginal bleeding in the meantime, an ultrasound will be done then to find out what's going on.
What will happen if my previa persists?
If the follow-up ultrasound reveals that your placenta is still covering or too close to your cervix, you'll be monitored carefully, have regular ultrasounds, and need to watch for vaginal bleeding. You'll be put on "pelvic rest," which means no intercourse or vaginal exams for the rest of your pregnancy. And you'll be advised to take it easy and avoid activities that might provoke bleeding, such as strenuous housework or heavy lifting.Bleeding from a placenta previa happens when the cervix begins to thin out or dilate (even a little) and disrupts the blood vessels in that area. It's usually painless, can start without warning, and can range from spotting to extremely heavy bleeding. If your bleeding is severe, you may have to deliver your baby right away, even if he's still premature. You may also need a blood transfusion.It's unusual for bleeding to start before late in the second trimester, and about half the time it doesn't begin until you're nearly full-term (37 weeks). The bleeding will often stop on its own, but it's likely to start again at some point. (If you have bleeding and you're Rh negative, you'll need a shot of Rh immune globulin, unless the baby's father is Rh negative, too.)If you start bleeding or have contractions, you'll need to be hospitalized. What happens then will depend on how far along you are in your pregnancy, how heavy the bleeding is, and how you and your baby are doing. If you're near full-term, your baby will be delivered by c-section right away. If your baby is still premature, he'll be delivered by c-section immediately if his condition warrants it or if you have heavy bleeding that doesn't stop.Otherwise, you'll be watched in the hospital until the bleeding stops. If you're less than 34 weeks, you may be given corticosteriods to speed up your baby's lung development and to prevent other complications in case he ends up being delivered prematurely.If the bleeding stops, and both you and your baby are in good condition, you'll probably be sent home. But you'll need to return to the hospital immediately if the bleeding starts again. If you and your baby continue to do well and you don't need to deliver early, you'll have a scheduled c-section at 37 weeks.No matter when you deliver, if you still have placenta previa, you'll need a c-section. With a complete previa, the placenta blocks the baby's way out. And even if it's only bordering the cervix, you'll still need a c-section in most cases because the placenta could bleed profusely if the cervix dilated.
What other complications can placenta previa cause?
Having placenta previa increases your risk of heavy bleeding not only during pregnancy but also during and after delivery. Here's why:After a baby is delivered by c-section, the obstetrician delivers the placenta and the mother is given Pitocin (and possibly other medications). This causes the uterus to contract, which helps stop the bleeding from the area where the placenta was implanted. But when you have previa, the placenta is implanted in the lower part of the uterus, which doesn't contract as well as the upper part — so the contractions are not as effective at stopping the bleeding.Women who have placenta previa are also more likely to have a placenta that's implanted too deeply and doesn't separate easily at delivery (placenta accreta). Placenta accreta occurs in only one out of 2,500 births overall, but your chances of having this problem are one in ten if you have placenta previa when you deliver your baby. Placenta accreta can cause severe bleeding, and a hysterectomy to control the bleeding and a blood transfusion may be required.Finally, women with placenta previa are more likely to have a low-birthweight baby — mostly because they may need to deliver early, but also because of a slightly increased risk of intrauterine growth restriction.
Who's most at risk for placenta previa?
Most women who develop placenta previa have no apparent risk factors. But if any of the following apply to you, you're more likely to have this complication:• You had placenta previa in a previous pregnancy.• You're pregnant with twins or higher-order multiples.• You've had c-sections before. (The more c-sections you've had, the higher the risk.)• You've had some other uterine surgery (such as a D&C or fibroid removal).• You're a cigarette smoker.• You use cocaine.Also, the more babies you've had and the older you are, the higher your risk.
