Normal and High-risk pregnancies
Your due date is an estimate of the date of delivery and determined based on the date of your last period. Your physician uses this date to assess the progress of your pregnancy and baby’s growth in the womb. The due date may be confirmed or updated after ultrasound is performed between 18 and 20 weeks of pregnancy. Usually the due date is 40 weeks after the first day of your last period with most babies arriving between 37 and 41 weeks. A post term pregnancy is described as lasting 42 weeks or more.
When a pregnancy exceeds 42 weeks, there is a small risk of the baby being stillborn. The causes for such deaths have not been established with certainty but probable reasons include reduced efficiency of placenta (tissue that provides nourishment to the foetus) and a decrease in amniotic fluid levels. Other risks to the baby include meconium aspiration, neonatal acidemia, low Apgar scores, macrosomia (excess birth weight) which can lead to birth injury.
The health of a baby not born by the due date is determined with the help of a few tests. Certain tests, such as a “kick count” can be done by the expecting mother herself. This test is a record of how often the mother feels the baby moving. Other tests such as electronic foetal monitoring involve measuring foetal heart rate and strength of uterine contractions by placing instruments under belts wrapped around the mother’s abdomen.
Most hospitals suggest inducing labour (causing a pregnant woman’s cervix to open and to prepare for vaginal birth) at 42 weeks. IV medications are used to bring on labour but if these fail, other methods are used, which include using prostaglandins (naturally occurring fatty acids) and special devices to soften and dilate the cervix, rupturing the amniotic sac to release the fluid, stripping or sweeping the amniotic membranes (thin membranes that connect the amniotic sac to the uterus wall) and using hormones for contracting the uterus.