Post-Due Date Testing
A normal term pregnancy may continue anywhere between 37 and 42 weeks, and it is not unusual for a woman to remain pregnant past her estimated date of delivery (EDD) at 40 weeks gestation. A pregnancy may be referred to as "late term" after 41 weeks and "postterm" after 42 weeks. Although it is a common occurrence to remain pregnant past your due date, there are certain increased risks during this period, mainly regarding the proper functioning of the placenta. To verify that the pregnancy is continuing on a normal and healthy path, you and your midwives may discuss and choose to do any of the following tests, usually on a twice-weekly schedule.
The nonstress test measures the fetal heart rate in response to fetal movement over time. The term "nonstress" means that during the test, nothing is done to place stress on the fetus (i.e. contractions). This test is typically done in our office using the Doppler to detect and count the baby’s heart rate. If two or more accelerations of the baby’s heart rate occur within a 20-minute period, the result is considered reactive or "reassuring.” If a nonstress test is conducted in the hospital or in another health care provider’s office, they may use a belt around your abdomen with a sensor that detects the fetal heart rate and records it graphically on a machine.
A biophysical profile (BPP) is an ultrasound exam that uses a scoring system to evaluate fetal well being in these five areas:
1. Heart rate
2. Breathing movements
3. Body movements
4. Muscle tone
5. Amount of amniotic fluid
Each of the five areas is given a score of 0 or 2 points, for a possible total of 10 points. A score of 8-10 is reassuring. A score of 6 is equivocal (neither reassuring nor nonreassuring). If you have an equivocal score, depending on how far along you are in your pregnancy, you may choose to have another BPP within the next 12–24 hours. A score of 4 or less means that further testing is needed. Sometimes, it means that the baby should be delivered early or right away. No matter what the score is, not enough amniotic fluid means that more frequent testing should be done or sometimes that delivery should be considered.
Other testing that may you and your midwives may consider includes Doppler velocimetry of the umbilical artery and a contractions stress test, which can be discussed at length if they are recommended.