The following is a brochure that I made for my doula course. If you would like copies to share, please let me know :)
Q. How is a due date determined?
A. The modern 40 week due date is based upon Naegele’s rule which assumes that all pregnancies last for about 280 days from the first day of the last menstrual period.
Q. Are due dates accurate?
A. Naegele’s rule assumes that all women have a 28 day cycle and ovulate on day 14, however, this is not true of all women. Some women have significantly shorter or longer cycles. One of the dangers of making this assumption for all women is that if a woman with a longer cycle were to have her baby forced out prematurely based on the LMP (last menstrual period) the baby could have long term consequences from the premature birth.
Q. What about due dates found by ultrasound?
A. When a woman’s LMP is unknown, ultrasounds are often used to find an EDD (estimated due date). Ultrasound scans taken early on in the pregnancy have an EDD accuracy of +/- 4-5 days at 12 weeks gestation, whereas, scans taken past 12 weeks only have an accuracy of +/- 7-10 days.
Q. Are most babies born on their due date?
A. If pregnancies are left to themselves, 50%-80% of them will continue past 40 weeks. Only 5% of babies are born on their due date with 10% arriving after 42 completed weeks.
Q. What are the risks of going past your due date?
A. The greatest concerns for pregnancies continuing past 40 weeks gestation are Postmature Syndrome and an increased risk of stillbirth. Postmature Syndrome is caused by the placenta failing to provide adequate nutrients for the growing baby. Symptoms of Postmature Syndrome range from minor ones such as longer fingernails and toenails to more severe symptoms such as impaired breathing or meconium aspiration. The risk of stillbirth has a slight increase as the pregnancy continues past 40 weeks with a .12% at 40 weeks and .2% at 42 weeks. However, most studies show that up to 25% of these stillbirths are directly related to genetic abnormalities and not to being postdate.
Q. What tests are offered after you pass your due date?A. Routine tests that are offered by active management caregivers include a Nonstress Test (NST), Amniotic Fluid Index (AFI), and Biophysical Profile (BPP). A Nonstress Test can show if a baby is responding well to stimulus by an increase in the baby’s heart rate during 20 minute intervals. An Amniotic Fluid Index gives a rough estimate of the amount of amniotic fluid. A Biophysical Profile includes both of these tests. Because there are so many variables to their reliability and the fact than none of these tests can predict events such as cord prolapse or placental abruption, there is no data to show that using these types of monitoring improves pregnancy outcomes.
Q. When should you consider induction?
A. When your caregiver will recommend induction will most likely depend on whether or not you have chosen an active or expectant management caregiver. While most active management caregivers routinely induce at 41 weeks, the American College of Obstetricians and Gynecologists do not recommend routine induction in low-risk pregnancies until 42 weeks. Because inductions themselves carry a whole host of risks, most expectant management caregivers, specifically those who follow the Midwives Model of Care, will take a more wait-and-see approach and will avoid induction unless they believe it is indicated. Having a comfortable relationship with your caregiver where you make the decisions, your concerns are addressed, and your questions are answered is the surest way that you can avoid an unnecessary induction.