What's the deal with a due date?


What's the deal with a due date?

by: Laura Barbour, Japan Birth Resource Network | .
Birth Ed. Center of Okinawa | .
published: April 12, 2016

“Are you still pregnant? Haven’t you had your baby yet? It’s dangerous going past your due date.” Those are just a few of the well meaning remarks that come from family, friends, even strangers at the end of a pregnancy.

When a woman is 40 weeks pregnant and her due date is here, our culture is conditioned to believe that the family should be holding their new baby…. or so we’ve heard.

According to evidencebasedbirth.com, baby’s gestational time can be anywhere between 37 weeks and 42 weeks. That is a 5 week gap of baby’s due date; it’s really a due month.

Where did the term due date originate from? “The 40 week due date is based upon Naegele’s Rule. This theory was originated by Harmanni Boerhaave, a botanist who in 1744 came up with a method of calculating the EDD based upon evidence in the Bible that human gestation lasts approximately 10 lunar months. The formula was publicized around 1812 by German obstetrician Franz Naegele and since has become the accepted norm for calculating the due date. There is one glaring flaw in Naegele’s rule. Strictly speaking, a lunar (or synodic – from new moon to new moon) month is actually 29.53 days, which makes 10 lunar months roughly 295 days, a full 15 days longer than the 280 days gestation we’ve been lead to believe is average. In fact, if left alone, 50-80% of mothers will gestate beyond 40 weeks.” From The Lie of the EDD: Why Your Due Date Isn’t When You Think.

As all women do not have the same menstrual cycles or ovulation cycles, women cannot be grouped into a one birthing date fits all group. Inductions that are not medically necessary create more problems for both moms and babies. Inductions should be based only on a mother to mother basis and not routine care. Studies have shown that only 3-5% of women deliver their babies on their due dates.

The American College of Obstetrics and Gynecology stance on induces states, “There are several important principles to consider in the timing of delivery. First, the decision making regarding timing of delivery is complex and must take into account relative maternal and newborn risks, practice environment, and patient preferences. Second, late-preterm or early-term deliveries may be warranted for either maternal or newborn benefit or both. In some cases, health care providers will need to weigh competing risks and benefits for mother and newborn; therefore, decisions regarding timing of delivery must be individualized. Additionally, recommendations such as these are dependent on accurate determination of gestational age.”

Medical care providers generally monitor women more closely past their estimated due dates (past 40 weeks plus in pregnancy) sometimes using further medical testing. They typically use a non stress test or a biophysical profile. The non stress test is a test where the mom wears fetal monitors and pushes a button each time she feels the baby move. This causes a mark to be made to compare to baby’s heart rate. The biophysical profile is a combination of a continual fetal monitoring test and an ultrasound. The added bonus to this test is the amniotic fluid levels and how well the placenta is functioning. These two tests allow medical care providers to determine how baby is doing inside mom.

New mom, Erin, recently gave birth to her third baby and said about her birth, “This is my third birth and my first two were delivered “past due” at military base hospitals. I was offered cesareans and when I declined, I was given an induction date at 41 weeks. Thankfully, my labor started naturally for both. I felt that my third baby would be around the same timeline but he took longer. At 40 weeks I started receiving messages of excitement from friends and family and at 41 weeks I received questions of when the induction would be and some concern. This was when I started “talking” about patience. At my last appointment, we monitored the baby and my condition. Everything was normal and progressive. I felt calm and confident after my appointment that everything was progressing just as it was meant to be. After my 42 week appointment, everything looked good. Dr said that there is no need for any induction yet: There was plenty of amniotic fluid, the placenta looked good, baby had good activity and a great heartbeat. 42 weeks was just a number. 3 days later my labor started and 5 hours after it started, Talon was born. I think the most important thing to ensure is that your birth support system has the same expectations for your labor and delivery as you do. A healthy baby is the end goal, but the mama’s experience is just as important. This includes the decisions made for inducing labor or waiting patiently. She (the mom) shouldn’t be pressured or scared into making decisions that she isn’t confident and educated about. We never forget our birth experiences.”

Just as it’s normal to go past the 40 weeks mark, some moms deliver their babies prior to that due date. Babies born at 37 weeks, 0 days and 38 weeks, 6 days are considered early term babies.

First time mom, Erica, recently had her first baby at exactly 37 weeks. She said, “Many of our friends who were expecting went early and my husband kept saying we would be early as well. I kept telling our baby to wait until 37 weeks since that is considered “full term”. I told baby whenever she/he was ready, I’d be ready to greet her/him (we didn’t know baby’s gender till birth). Of course, I wanted baby to stay cozy until she/he was fully developed and ready for the world. Well, she listened to her mom, and at 37 weeks exactly my labor started. I was not afraid that was too early. I knew we were ready. I do believe that having a smaller baby made my delivery easier, but I will say, she has made up for it in a few extra steps we had to take to get he up to scruff! Trust that your body and your baby know what they are doing and that everything will turn out fine. Make sure to have your hospital bags packed and anything ready to go.”

Traditionally due dates should not be changed after the first trimester of pregnancy. ACOG states that “Subsequent changes to the estimated due date should be reserved for rare circumstances, discussed with the patient, and documented clearly in the medical record.” There should be few circumstances when a doctor changes a mom’s due date in the third trimester.

“Inducing labour involves making your body/baby do something it’s not yet ready to do. Before agreeing to be induced, be prepared for the entire package, i.e. all the steps. You may be lucky enough to skip one step, but once you start the induction process, you are committed to doing whatever it takes to get the baby out, because by agreeing to induce, you are saying that you or your baby are in danger if the pregnancy continues. An induced labour is not a physiological labour, and you and your baby will be treated as high risk — because you are.”
 — Doctor Rachel Reed

Telling your friends and family your due month is probably a better idea than a specific due date. After all, patience is the first lesson your baby will teach you.

Works Sited:


Connect with local Okinawa moms on Facebook in “Pregnancy & Birth Talk Okinawa”
Japan Birth Resource Network provides evidence based information and mother friendly support throughout Okinawa and Japan. To learn more visit: www.japanbirthresourcenetwork.com

Birth Education Center of Okinawa’s April Schedule

  • Monday, April 18 - Finding Fertility Support Group
  • Monday, April 25 - Breastfeeding Basics
  • The BEC offers a Weekly Wednesday Weigh In every week for breastfeeding mothers & baby, IBCLC consultations, Hypnobirthing, Infant Massage, and more.