Post-Term Pregnancy: Why Being Too Far Past Your Due Date Is Bad

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You always hear a lot about premature births and the problems of having a baby that is born too soon. But post-term births, sometimes called postmature births, can also present problems for both mother and baby.

A post-term pregnancy is one that has gone at least to 42 weeks, which is two weeks past the expected due date for the baby. We’ve discussed how your due date is calculated here. Calculating your due date is based on when you had your last period and on ultrasound images of your baby taken in the first few months of your pregnancy. Your calculated due date is reasonably accurate, but it is still just an estimate, which is why your baby may arrive up to three weeks before or two weeks after and still be considered a full-term baby.

So what could be so bad about the baby just staying in place in your uterus for an extra couple of weeks? One problem is that the placenta has an expiration date. The placenta is the organ that forms in your uterus along with your baby and that provides him or her with oxygen and nutrition from your bloodstream. When a pregnancy has gone on too long, the placenta starts to lose some of this ability to nourish your baby.

Other problems also develop. There may not be enough amniotic fluid in your uterus, and the weight of your baby can start pressing on his or her umbilical cord, interfering with the blood flow from the placenta. The baby may also start to have bowel movements, which puts a substance called meconium into the amniotic fluid where he or she could aspirate it.

The size of your baby is another issue when you are post-term. Your baby may keep growing, and a larger baby makes it more likely that you will need a cesarean section for your delivery.

What to Do?

The first thing that your obstetrician or midwife will do if you are past your due date is take stock of the situation. Your healthcare provider will run several tests to check on your health and the health of your baby.

One simple test is a kick count, which measures how often your baby is moving. As the name states, it is a simple count of how often your baby is kicking or moving.

You may be asked to come to your healthcare provider’s office for electronic fetal monitoring. Small sensors will be strapped around your belly that measure your baby’s heart rate. The also measure your contractions, if you are having any, and how strong they are.

Your healthcare provider may also have another ultrasound performed to check on the size of your baby and the amount of amniotic fluid present around him or her.

If all looks well and it is still before 42 weeks, most obstetricians and midwives will let a pregnancy continue. But at 42 weeks, if there are no signs that labor will begin soon, steps may be taken to induce labor. Your healthcare provider may perform a minor procedure called stripping the membranes, which means that he or she will insert a finger into your cervix to detach the amniotic membrane from the wall of the uterus. This will often start your contractions. He or she may also rupture the amniotic sac, which can also start your labor.

In addition to these methods, your obstetrician or midwife may give you medications including prostaglandins or oxytocin. Prostaglandins are hormones that can help dilate the cervix of your uterus and can help start contractions. Oxytocin is another hormone and also helps start contractions.

Remember, even if you are several days or more than a week past your due date, your baby may be totally fine. Some women are simply more likely to take a bit more time in their pregnancies. If your first baby was late, your others might be, too.

Valerie DeBenedette
Valerie DeBenedette is an experienced health and medical writer who lives about an hour north of New York City with a dog that is smaller than her cat. Her work has appeared in magazines, newspapers, newsletters, and on websites. She is a member of the National Association of Science Writers.

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