Today, would have been my calculated due date for my second daughter – Ivy Pearl, had she actually been born on this day three years ago. The date my midwife calculated was April 16th. The day she was born was April 28th. The birthing process began on April 26th. I was pretty confident that the due date was accurate. Despite having very irregular menstrual cycles, I knew the day that I conceived. It was obvious to me what was going on in my body that day. Clearer than anything of the sort had ever been before.
However, to actually expect Ivy to be born on that day was a long-shot.
Even if you know your exact date of conception, and the exact gestational age of your baby, and know the “average” length of pregnancy, it is still difficult to predict exactly when your baby will be born. A normal pregnancy can last anywhere from 37 to 42 weeks. Only 4% of babies are actually born on their “due dates”. 6-10% of babies are born early – prior to 37 weeks; 4-14% of pregnancies last more then 42 weeks. -Janelle Durham (Transition to Parenthood)
Read more about how due dates are calculated (because there are several different ways) at Transition to Parenthood.
In a healthy pregnancy, there is no real concern in allowing your pregnancy to continue past the “due date”. Actually, you must reach the 42 week mark before you can consider yourself overdue.
It has become relatively common to receive an ultrasound in the last trimester to check on the baby’s size. This practice can be very misleading and can lead to unnecessary intervention (such as induction and cesarean surgery) in a healthy pregnancy.
Most ultrasound resources state that ultrasound for determining gestational age in the first trimester is accurate to within about a week. Measurements in the second trimester are supposed to be accurate to within about two weeks. By the third trimester, the accuracy rate has dropped significantly and can be off by as much as three weeks. (Read more about ultrasound use and accuracy for determining fetal size here.)
Even early pregnancy ultrasounds should only be used to estimate the general timing of prenatal care, and not to put a end date on a pregnancy.
Your healthcare provider will use hormone levels in your blood, the date of your last menstrual period and, in some cases, results from an ultrasound to generate an estimated gestational age. However, variations in each woman’s cycle and each pregnancy may hinder the accuracy of the gestational age calculation. If your healthcare provider uses an ultrasound to get an estimated delivery date to base the timing of your prenatal care, the original estimated gestational age will not be changed.
It is thought that it is the baby that initiates labor by releasing a hormone that reacts to the mother’s hormones. This hormone is released when the baby’s brain and lungs are mature enough for life outside of the womb. Inducing or scheduling a c-section without a medical emergency any sooner than 39 or 40 weeks is dangerous for your baby, and could result in he or she being born premature.
The healthiest and safest decision in a normal pregnancy for both mother and baby is to let labor begin on its own.
It might be more accurate to think of your pregnancy in terms of “birth month” instead of “due date.” The anxiety and pressure of having a due date is not worth the cost of making decisions solely based on when it was thought that your baby might come.
If you are having trouble relaxing about your due date, or the real possibility that your pregnancy will continue past the due date, read this post from Birth Without Fear. The Mayo Clinic also gives some great advice on how to relax and stay patient during those final weeks.
I am forever thankful for my midwife’s patience in regards to waiting for Ivy to come on her own. When care providers place undue pressure on healthy, expecting mothers around the topic of due dates, it creates anxiety where there is not a need for concern. The best way to create a comfortable environment for late pregnancy is to find a care provider that is comfortable with a healthy pregnancy lasting beyond 40 weeks, sharing with friends and family not a due date, but a due month, and avoiding ultrasounds that are not medically necessary.
Many happy days to you and yours,