Post Dated or Post Term Pregnancy


Post Term Pregnancy - What to watch out if you are overdue?

A due date is an estimated date calculated by the doctor based on the date of your last period. It is usually 40 weeks after the first day of the last period. The date changes or becomes more accurate based on the ultrasound scans that happen as the pregnancy progresses. Majority of the babies arrive between 37 and 41 weeks, usually a week on the either side of the due date. Twins and multiples arrive much before that.

What is a post term pregnancy?

The normal duration of pregnancy is 37 to 42 weeks, which is referred to as “term pregnancy”. A postterm pregnancy or a prolonged pregnancy, is a pregnancy that extends beyond 42 weeks or 294 days from the first day of your last menstrual period. As many as 10 percent of women deliver postterm. Many hospitals, especially in India have the policy of inducing labor if the pregnancy beyond 40 weeks.

Causes of a Postterm Pregnancy

For most cases the reasons for a post term pregnancy are unknown. However, there are some factors that place a woman at a higher risk than others. The probability of a post term pregnancy is higher in first pregnancies and also among women who have had postterm pregnancies previously as well. Genetic factors sometimes may also play a role. One study has revealed an increased risk of postterm pregnancy in women who were born postterm themselves.

A lot of times though, calculation errors may be the reason to believe that you have a postterm pregnancy, when in reality it may not be so. It could just be that you made a mistake in calculating your due date. In such a case an ultrasound performed in your first trimester may be the most reliable way of calculating the due date of the baby.

Risks involved in a post dated pregnancy

A post term pregnancy is associated with several risks to the baby as well as the mother.

Risks to the baby

Stillbirth — The occurrence of stillbirth or infant death increases in pregnancies that go beyond 42 weeks. However, that risk is relatively small, with only 4 - 7 deaths per 1000 deliveries. In comparison, the risk of stillbirth in full term pregnancies or ones between 37 and 42 weeks is 2 to 3 per 1000 deliveries.

Large body size — Postterm babies have a higher chance of developing complications which relate to large body size, such as weighing in excess of 10 pounds. Complications from a large baby include prolonged labor, difficulty for mother having a vaginal birth, or birth trauma.

Fetal dysmaturity — This is also referred to as the "postmaturity syndrome," where the baby’s growth in the uterus is restricted, usually because of inadequate blood supply through the placenta.

Meconium aspiration — Post Term babies are is more likely to have an intrauterine bowel movement, called meconium. When the fetus is stressed, there is a strong chance of the baby consuming some of this meconium, which could lead to breathing problems for the baby after birth.

Risks to the mother

Risks to the mother mostly are related to the large size of postterm babies, difficulties during labor and an increased probability of injury to the perineum area. Also the chances of a C-section become much higher in the case of a post-term pregnancy.

What to do in case my baby is overdue?

If you haven’t had your baby by the time you are 41 weeks, your doctor will give you an antenatal check up where your doctor will check your due date and confirm it. Your doctor will monitor you closely about twice a week now just to make sure that your baby is doing well. Your doctor may recommend one or more of these tests:

  • Non-stress test, using a fetal monitor to check your baby's heart rate
  • And Ultrasound to make sure of your baby's growth and adequate movement
  • Measuring the amniotic fluid
  • Examination of your cervix to check whether it has started to thin out and dilate in preparation for delivery
  • She may perform a membrane sweep to see if it triggers a membrane sweep.