Ah..the due date. The question everyone always asks. “When are you due?” Of course this day is then circled, highlighted and little stars are drawn around it on your calendar. It is so easy for the awaiting mother (and not to mention her family) to get very attached to this date. However, According to the American College of Obstetricians and Gynecologists (ACOG), only 5% of babies arrive on the exact due date.
Full term gestation is seen as 37-42 weeks- so it’s more like a due month than a due date. There are a few different ways to determine a due date. One way is by ultrasound and another is by measuring the uterus. The third and commonly used method is called the Naegle’s rule, in which the due date is calculated by taking the first day of your last period, counting back three months, and then adding seven days. This calculation is assuming that every woman regularly has a 28 day cycle and ovulates on day 14. If the pregnant mom has a longer cycle, therefore ovulating later, she will likely have a longer gestation period and her given due date may be off. A study done through the department of Epidemiology at Harvard School of Public Health concluded, that when estimating a due date for private-care white patients, one should count back 3 months from the first day of the last menses, then add 15 days for primiparas [first time mother] or 10 days for multiparas [mother that has already given birth] , instead of using the common algorithm for Naegele’s rule.
Given the wide range of interpretation and accuracy of determining the due date, it is important to discuss with your health practitioner what his/her protocol is for passing the due date. Throughout my years working with the pregnant population, I have encountered some care providers that allow up to the full gestation period of 42 weeks before induction, while other care providers induce 10 days, one week or one day after the due date.
If the mother passes her due date of 40 weeks and would like more time before a conversation ensues about induction, she can ask can try some natural alternatives to induce labor. If the care provider is open to the mother’s need for more time, the expectant mother will likely go through a battery of tests to assure the continued health of both herself and her child.
Kick counts This is a completely noninvasive test that can be done at home, and can be reliable way to keep track of the baby’s well being. The mother is to count the kicks from the baby in a given time and keep track of the pattern. ACOG recommends to write down how long it takes the baby to make 10 movements.
Nonstress test This test is measuring the baby’s heart rate at rest and during an active period. It is done with an EFM (external fetal monitor) and an external monitor measuring uterine contractions.
Biophysical Profile This test combines the results of the nonstress test and an ultrasound machine to give the measured volume of amniotic fluid and to check the baby’s breathing, movement, heart rate and muscle tone.
Contraction Stress Test This test will measure the baby’s heart rate during a contraction to asses how the baby is handling the reduction of oxygen during the contraction.
Mother’s Blood Pressure and protein in urine The care provider will continue to monitor the mother’s blood pressure and check for protein in the urine to assure the mother is not developing pre-ecclampsia.
It is rather uncommon to actually pass 42 weeks of gestation. In fact, only about 7% of babies are not delivered by that point. Pregnancies bypassing the 42 week marker are referred to as “post-term pregnancy.” Note “post term pregnancy” is NOT defined as simply passing the due by a few day, but passing it by a significant amount of time. For mothers that do pass the 42 week mark, the care provider will likely want to induce labor to avoid serious complications that can arise with post-term pregnancies.
