This Is How to Apply Naegele’s Rule to Predict a Due Date

yawning baby
Photo by Tim Bish on Unsplash

Yesterday, we had a woman in class who was one day past her due date. She had a look of defeat on her face and was completely unsettled by the situation. She explained that her first baby was two weeks early so she had expected the same would be true the second time around. There is so much build and anticipation around a due date; yet, only about 5% of women actually give birth on that particular day.

How are due dates predicted?

There is a formula known as “Naegele’s Rule” which helps care providers come up with the estimated due date. The formula is as follows:

Last menstrual period (LMP) + 7 days – 3 months = Due Date!

So for example, May 15th (LMP) + 7 days (May 22nd) = February 22nd! With the current formula, about 2/3 of babies are born within ten days of their due dates, and approximately 80% of babies born sometime between week 38 and 42 after LMP. This formula uses a baseline of a 28-day cycle with ovulation occurring on day 14. The length of a woman’s cycle is generally not taken into consideration when using Naegele’ Rule.

Ultrasound is another means to determine gestational age. In the first trimester, ultrasound estimation of gestational age is actually more accurate than later in pregnancy. During this time period, care providers measure crown to rump length through the use of a transvaginal ultrasound as opposed to transabdominal ultrasound. In the second and third trimester, transabdominal ultrasound measures the biparietal diameter, head circumference, abdominal circumference, and femur length. However, these measurements are believed to be less accurate due to natural variations such as skull shape, ethnic background effecting femur length and the abdomen may measure asymmetrically.

But in general, ultrasound is believed to be more accurate than Naegele’s Rule. If a care provider takes ultrasound results – which have proven to be more precise and accurate – into consideration when determining the due date, it may help reduce induction for “post date” babies or other fetal interventions such as fetal growth restriction or macrosomia (big baby!).

Why is it a problem to pass a specific due date?

The issues a woman faces after passing her due date can range from simply feeling disappointed to facing multiple stress tests and pressure to induce. These factors can increase anxiety, which is not helpful to start labor naturally. I have known some care providers who wish to induce on the due date, or within days of it. It is important to have a conversation with your care provider regarding their protocol for passing one’s due date.

What to do if approaching full term?

I recommend talking to your care provider about how far past your due you can go without medical intervention. There are 3 questions that are instrumental in starting this conversation: Is mother OK? Is baby OK? Can we have more time? If the answer is “yes” to the first two questions, it may lead to your care provider giving you more time than originally expected.

There are also some natural methods to help induce labor. Some of these suggestions can be done on your own, while others require a trained professional or your care provider. Here is a short laundry list of suggestions:

  • Sex: The release of semen onto the cervix can aid in softening it since it contains the hormone prostaglandin.
  • Acupuncture: There was a study done through the Department of Obstetrics and Gynecology at the University of Vienna, Austria to evaluate whether acupuncture at term can influence cervical ripening, induce labor and thus reduce the need for postdates induction
  • Stripping the Membranes: THIS PROCEDURE NEEDS TO BE PERFORMED BY A MIDWIFE OR DOCTOR!!!! This procedure is done by the doctor or midwife inserting two fingers inside the cervix and separating the amniotic sac from the cervix. This may stimulate the body’s natural production of prostaglandin.
  • Relaxation: You can go ahead and try all the methods listed above, but if you are stressed and tense, chances are they will not produce the desired effect. Your body needs to be relaxed and calm for it to open.

Hopefully this has shed light on the accuracy of due dates and has eased some pressure you may be feeling surrounding the arrival of your little one. Here is the advice I always give to moms who have passed their due dates: Go out and enjoy yourself! See a movie, have a date night, sit down and read a book, go get a manicure and pedicure. These small events may fall by the wayside as you transition into life with your new baby.

Happy birthing!!

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Debra Flashenberg, CD(DONA), LCCE, E-RYT 500 is the director of the Prenatal Yoga Center. She has spent most of her life performing and was introduced to yoga through a choreographer in 1997. After several years as a yoga student, she decided to continue her education and became certified as a Bikram Yoga instructor. After being witness to several “typical” hospital births, Debra felt it was important to move beyond the yoga room and be present in the birthing room. In 2006, Debra received her certification as a Lamaze® Certified Childbirth Educator. In September of 2007, Debra completed a Midwife Assistant Program with Ina May Gaskin, Pamela Hunt and many of the other Farm Midwives at The Farm Midwifery Center in Tennessee. Drawing on her experience as a prenatal yoga teacher, labor support doula and childbirth educator, Debra looks to establish safe and effective classes for pregnancy and beyond. She is the proud (and tired) mother of baby boy, Shay.

The views and opinions expressed on this blog are purely the blog contributor’s. Any product claim, statistic, quote or other representation about a product or service should be verified with the manufacturer or provider. Writers may have conflicts of interest, and their opinions are their own.

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