A pregnancy is considered “post-term” if the mother is two weeks or more past her due date and still has not gone into labor. Although the normal duration of pregnancy is 40 weeks, every woman, every baby, and every pregnancy is unique, and about 5 percent of pregnancies continue post-term.
While a post-term pregnancy may be frustrating (“Forty-plus weeks and I’m still pregnant?”), it is not usually a cause for serious concern until after the 42-week mark.
If your baby is overdue, it is possible that you may have miscalculated the date of your last menstrual period, which could mean that you have not been pregnant for as long as you and your doctor may have believed. This is extremely rare in the modern, developed world, however, since the advent of ultrasound and other techniques that can be used to estimate the gestational age of a fetus. The age of the fetus can also be estimated by the date the mother first feels movement, by the date when the fetal heartbeat can first be detected, or by the size of the uterus.
Causes of Post-Term Pregnancy
The phenomenon of post-term pregnancy is not as well understood as most doctors would like it to be; in most cases, the reason why a baby is overdue is unknown. There are certain risk factors, however, that correlate with post-mature birth:
- Previous post-term pregnancy
- Irregular menstrual periods
- First pregnancy
- Maternal obesity
- Family history of post-term pregnancies
Risks and Complications
Fortunately, most post-term babies are born healthy, although there are some possible complications associated with this condition. After childbirth, signs of post-term pregnancy can often be seen in the baby, whose skin may be dry and peeling. The fingernails and toenails may be overgrown, and there may be noticeable creases in the baby’s palms and in the soles of his or her feet. Post term babies also have a higher incidence of meconium passage, which is a fetal bowel movement. Meconium-contaminated amniotic fluid could lead to breathing problems if the baby gets some into their lungs.
Risks to Mother
- Delivery may become complicated if the baby grows too big before it is born, and a C-section delivery may be necessary.
- There is an increased risk of infection, birth-related injury and postpartum hemorrhage (bleeding).
Risks to Baby
- There may be a decrease in amniotic fluid, which can in turn cause problems with the umbilical cord.
- Hypoglycemia (low blood sugar)
- After 42 weeks, there is the danger of neonatal meconium aspiration syndrome. Meconium is the infant’s first bowel movement, and if this occurs in utero it is possible for the amniotic fluid to be contaminated and subsequently inhaled by the fetus.
- Stillbirth, or neonatal death, occurs in one out of every 1,000 pregnancies that reaches 40 weeks, but the death rate doubles after 42 weeks.
At first, your doctor may only want to continue to monitor your pregnancy. He or she will probably want to check your cervix regularly to see whether it’s begun to thin and dilate, which it will do when labor is near. The doctor may also want to administer a fetal non-stress test in order to ensure that the baby is still getting enough oxygen and nutrients from the placenta, which may have begun to function poorly by this point. This is usually done two times per week after 40 weeks.
At 41 weeks, your doctor may begin thinking about when to induce labor. If the baby is properly responsive to the fetal non-stress test, and ultrasound shows nothing abnormal, the doctor may decide to wait for you to go into labor on your own. After 42 weeks, however, the risks to mother and baby become greater, and induction will be necessary. If the doctor is unsuccessful in inducing labor, a C-section may be required.
As noted above, most post-term pregnancies end in the birth of a perfectly healthy baby. It is important, however, to see your ob-gyn regularly throughout your pregnancy so that your due date can be estimated as accurately as possible.
Talking to Your Doctor
If you are concerned that your pregnancy is overdue, it may be a good idea to discuss it with your doctor. Here are some questions you can ask to begin the conversation:
- I’m not sure exactly when I got my last period; is it still possible for you to accurately estimate the gestational age of my baby?
- What does a fetal non-stress test tell you about my baby’s health?
- How long do you think we should wait after my due date before inducing labor?
- Will I need to have a C-section delivery?
- Is my baby now too big to deliver vaginally?
- Is it still possible for me to deliver on my own, without inducing labor?