By Georgia Ragonetti-Zebell, MD
My fourth baby was due on January 1. I was certain that he would be early. A Christmas baby would be fun, I thought. But Christmas came and went…and so did the New Year. Every day, I got texts and phone calls, asking when I would be induced. For example, this exchange from my wonderful nurse:
As if being pregnant for a million years isn’t hard enough, the pressure of everyone knowing your expiration date just intensifies it. I think the due date is one of the most misunderstood parts of pregnancy. It is just a guess, or an average estimate, but it does have implications for a healthy pregnancy. Everyone understands that having a baby too early can be dangerous, but what about too late?
First, some definitions:
Early term: 37 weeks and 0 days to 38 weeks and 6 days
Full term: 39 weeks and 0 days to 40 weeks and 6 days
Late term: 41 weeks and 0 days to 41 weeks and 6 days
Postterm: 42 weeks and 0 days or later
Wow. That seems really picky. But the reality is that babies born in this 5 week range have differing health risks depending on WHEN they were born.
In the absence of medical problems, such as pre-eclampsia, growth restriction, and diabetes, babies need to bake until full term. Babies that are born before 39 weeks are at increased risk for breathing problems, including pneumonia and respiratory failure. They are more likely to be admitted to the NICU and to require a ventilator. Neonatal mortality is also higher for babies born before 39 weeks.
Ok, so bake as long as possible, right? Wrong. Babies born 42 weeks or later are at increased risk for seizures, meconium aspiration, and a 5 minute Apgar less than 4. They are twice as likely to be admitted to the NICU. Babies born after 42 weeks are also more likely to be macrosomic, or large for their age. This leads to increases in operative vaginal delivery (forceps or vacuum delivery), cesarean delivery, and shoulder dystocia.
The most concerning risk of late term and postterm pregnancies is the risk of stillbirth. The overall rate is low, but it increases with each week as the pregnancy continues. After 41 weeks, the stillbirth rate is 1.5 times as high as it is at 40 weeks. At 42 weeks, it is 1.8 times as high, and at 43 weeks it is 2.9 times as high!
What about risks to momma? Women are more likely to have severe perineal lacerations (due to those big babies!) as well as infection and postpartum hemorrhage. One of the most interesting findings in the research about overdue babies is that the cesarean delivery rate is HIGHER in women who deliver after 41 weeks. This is one of the reasons doctors often recommend induction starting at 41 weeks.
So how do we prevent going late term or postterm? The first thing to do is establish an accurate due date. We know that pregnancies average 40 weeks from the last menstrual period. That assumes a 28 day cycle and that you can actually remember the first day of your last period. That gives us a 9.5% postterm rate. But, with the wonders of modern technology, we can do better. If you have an early (first trimester) ultrasound to confirm, the rate is decreased to just 1.5%!
Another thing to consider is membrane sweeping, which is what I was having done at the appointment I mentioned in my text above. Membrane sweeping is done during a cervical exam. It involves separating the bag of water from the cervix and lower uterine segment to help stimulate labor. Membrane sweeping significantly reduces the number of postterm pregnancies.
And it worked for me! Later that night, I went into labor and delivered my big boy just before midnight. So if you’re feeling the pressure of the expiration date, be patient for another week or two and think about having your membranes swept. Know that your c-section rate may be lower if you deliver by 41 weeks. And even though it feels like it, you will not be pregnant forever. I promise.
Georgia Ragonetti-Zebell, MD is an OB/GYN practicing in Upstate South Carolina, and is mommy to four (yes, FOUR) boys. She is a graduate of the Women’s Health Pathway at Drexel University College of Medicine in Philadelphia, Pennsylvania and completed her residency in Obstetrics and Gynecology with the Greenville Health System in Greenville, South Carolina. She has a special interest in natural childbirth, breastfeeding, and alternative methods in labor and delivery. She enjoys yoga, crochet, and reading, but spends most of her free time cleaning up poop while trying not to step on Legos.