An overdue baby is one who is yet to come well past the due date. A normal full term pregnancy extends up to 37 to 40 weeks which is around 280 days from the first day of the last menstrual period. A pregnancy lasting between 41 weeks and 42 weeks is called as late term and beyond 42 weeks is termed as post term pregnancy.
According to studies, very few women deliver on the due date. As most deliveries occur 1 to 2 weeks earlier or after the due date, 37 weeks to 42 weeks of pregnancy is considered as a term pregnancy nowadays.
Babies born around 37 to 40 weeks of pregnancy are in best of health and development at the time of birth. An overdue date pregnancy carries risk of serious health complications for the baby just like a preterm pregnancy. The chances of stillbirth and/or life-long health complications are high in an overdue baby.
Causes of past due date pregnancy
The exact cause for post-delivery is not known. However, certain risk factors are associated with overdue delivery which include:
- History of previous pregnancy going over due date
- Genetics and heredity – This is the most common risk factor post term pregnancy. A pregnant lady is likely to bear post term pregnancy if she herself was an overdue baby.
- A twin pregnancy with identical twins, especially with a pair of girls, is more likely to be over due date.
- First time pregnancy
- A pregnancy with a male baby can go past due date pregnancy.
- Late-age pregnancy beyond 30 years
- Errors occur in calculating the date of post term delivery when calculated using date of last menstrual period, especially when menstrual periods are irregular.
Complications in the baby due to overdue pregnancy
- Chances of the baby’s death during delivery or at birth (stillbirth) and shortly after birth (perinatal death) are high in an overdue pregnancy.
- Overdue baby tends to be large with a body weight more than 4.5 kg, i.e., fetal macrosomia, and can lead to shoulder dislocation and other physical injuries to the baby during birth.
- Post maturity or dysmaturity syndrome can occur and is marked by restriction in the baby’s growth after the due date of delivery. These symptoms arise as a result of insufficient blood supply to the fetus.
- Oligohydramnios or a decrease in the fluid surrounding the fetus is commonly associated with post term pregnancy. This leads to compression or hardening of the umbilical cord causing a decrease in oxygen and blood supply to the fetus.
- A post term infant usually has thin and dry skin; loose skin on thighs and buttocks, long nails and scalp hair, etc.
- Meconium aspiration may occur. It is characterized by passage of baby’s stools (meconium) into its lungs while in uterus before birth. Meconium aspiration causes breathing problems, increase in breathing rate, infection in lungs, etc.
- An overdue baby can also suffer from epilepsy, reduced blood sugar levels, etc. as it grows.
Overdue pregnancy risks for the mother
The mother with an overdue pregnancy is not risk-free either. Possible complications are as follows:
- Obstructed labour due to large size of the baby
- Tear and lacerations in the tissue due to prolonged labour
- Blood loss (postpartum hemorrhage) and blood clotting disorders due to surgical procedure in vagina to aid natural delivery.
- Increased chances of cesarean delivery
Management of overdue pregnancy
Monitoring the baby’s health before the delivery in an overdue date pregnancy includes monitoring the heart rate, movements and amniotic fluid volume. The following tests might be performed:
- Non-stress test to monitor the baby’s heart rate using an ultrasound.
- A biophysical profile (BPP) including non-stress test and ultrasound scan for monitoring fetal movements, breathing movements, fetal tone during different movements of arms, legs and spine and measuring volume of amniotic fluid.
- Contraction stress test (CST) to monitor fetal heart rate after uterine contractions are induced by injecting oxytocin to the mother.
Labour is induced in an overdue pregnancy to prevent stillbirth and other complications.