An expectant mother holds her belly with one hand and her back with the other.
Mom and baby can face additional health risks when the delivery date is extended too far. (For Spectrum Health Beat)

At first, it’s the excitement.

You get to decide how you want to share the news with others. Then you get to wear maternity clothes and, eventually, you get to feel wonderfully “big.”

Finally, it’s all about waiting for the baby to arrive.

There’s no doubt about it—pregnancy is one of the most exciting times for a woman.

But it doesn’t always go according to schedule.

We know that only about 4 percent of babies are born on their due date. In past stories, I looked at what happens when babies are born too early.

Is there a “too long” point?

Definitions have changed a bit, but a baby born anywhere from 41 weeks to just under 42 weeks (41 weeks and six days) is called a late-term baby. A baby born beyond 42 weeks is considered post-term.

I’ve learned some interesting things about late-term babies. Did you know that if the dad was a late baby, the new baby has a 23 percent chance of being born late? If the mom was a late baby, the baby has a 49 percent chance of being born late.

Also interesting: If you’ve had one late baby, you stand a higher chance of having another late baby.

A Netherlands study of more than 233,000 women found nearly 8 percent of women had a post-term baby in the first pregnancy. In their second pregnancy, 15 percent of them delivered late. Of the moms who had delivered a baby full-term, 4 percent later delivered a baby late-term.

Some things that can put you at risk for a beyond-term delivery:

  • It’s your first baby.
  • You’re a mom over the age of 30.
  • You’re a tall mom.
  • You’re expecting a baby boy.
  • Your baby has some possibly rare genetic issues.

These are all factors outside your control. Obesity is another factor that can put you at risk, but that’s the only factor that you could potentially control.


The medical world is more accurate these days in providing due dates to moms, given the use of first trimester ultrasounds. In the past, we primarily went by a mom’s last period.

A 2015 study found that using the first trimester to help confirm a baby’s due date can improve accuracy. These days, about 3 percent of babies are born post-date, compared to 12 percent in the past.

The early ultrasound, as opposed to ultrasounds done later, has been much more accurate for predicting due dates. This is because in the beginning, baby is growing rapidly and you can see the growth from week to week.

What are the risks to babies born post-date? There are concerns about a baby’s size. As a baby gets larger, it can make for a more complicated delivery.

Some other issues:

  • As the placenta ages, it may not feed a baby as well.
  • Meconium in the water. Meconium is what we call the first several bowel movements a baby has. A baby can swallow it.
  • The risk of stillbirth or death increases past 42 weeks.

There are risks to the mom, too, with a baby born post-date. Moms can suffer complications from a large baby at delivery, which can involve additional bleeding or tears. The situation can also prolong delivery and increase the chances of a C-section.

What can be done?

The American Congress of Obstetricians and Gynecologists says antenatal testing may be needed at 41 weeks. Many providers start non-stress tests after your due date has passed.

Typically, these tests are done twice a week, although sometimes weekly. A non-stress test involves placing a fetal monitor on mom and watching the baby’s heartbeat.

Other possible steps:

  • Stripping the membranes. Performed during a vaginal exam, this separates the membranes from the cervix.
  • Ultrasounds to check on fluid levels around the baby.
  • Inducing labor.