Risks of Pregnancy at Advanced Maternal Age

In the United States, advanced maternal age is defined as giving birth when you’re 35 years or older. Also called geriatric pregnancy—not the most flattering name—this experience is becoming more common worldwide. As couples delay childbearing based on economic, social, educational, or career pressure and the availability of birth control, fertility treatments, and childcare, researchers are learning more about what having babies when you’re older might mean for your and baby’s health.

Fertility decreases with age for both men and women, starting in earnest around your early 30s and speeding up as you pass 40. For this reason, if you have trouble getting pregnant on your own in your early 30s, it’s a good idea to seek help sooner rather than later, in case you need several rounds of fertility assistance. But as with all the risks we’re going to discuss, there’s not a hard age cut-off any time and most of the risks are still small overall, meaning that even if it’s more likely that you’ll experience anything we’re discussing here, there’s still not a big chance in the grand scheme of things.

As behavioral economist Emily Oster writes in her book, Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong—and What You Really Need to Know, “Your eggs don’t wake up on the morning of your 35th birthday and start planning their retirement party.”

In the same way that fertility gradually decreases, there are also pregnancy- and baby-related risks that gradually increase as you age. On the website Evidence Based Birth, Rebecca Dekker, a nurse researcher, and her colleagues looked at the data from lots of studies that compared the risks of outcomes for both pregnant people and their babies at different ages. You can read the whole article, which is called “Evidence On: Advanced Maternal Age.”

The first type of risk that Dekker and her colleagues describe is genetic risk. One example of a genetic-related risk is the risk of the baby having Down syndrome, where instead of just two copies of chromosome 21, they have three. Most genetic risks increase with age, with women over the age of 40 having the highest risk.

Another risk that is related to genetic risk, but also involves other factors, is the risk of miscarriage. It’s more common to have a miscarriage as you get older, at least in part because of the quality of your eggs, which deteriorates as you age. According to a study by epidemiologist Anne-Marie Nybo Andersen and colleagues published in the British Medical Journal in 2000 and referenced in the Evidence Based Birth article, fewer than one in 10 pregnancies end in miscarriage when the pregnant person is in their early twenties, but nearly three quarters of pregnancies do when the person is older than 45.

Stillbirth, which is the loss of a pregnancy after about 24 weeks, is also of concern as you get older. The Evidence Based Birth team describes studies from both the United Kingdom and Sweden, in which the risk of stillbirth for pregnant people over 40 was found to be about 1 in 100. This risk is lower if you’re not having your first baby after age 35. If you don’t have diabetes, high blood pressure, preeclampsia, or kidney, heart, or lung disease, you will have a lower risk of stillbirth, according to research published by Uma Reddy and colleagues in 2006 in the American Journal of Obstetrics and Gynecology.

Other pregnancy- and birth-related complications can also increase with age. Older mothers are more likely to develop gestational diabetes, postpartum hemorrhage, and placenta previa, where the placenta partially or fully covers the opening of the cervix through which baby must pass to be born vaginally. And the babies of older mothers are more likely to have low birth weight or be born prematurely.

Hearing all this evidence might feel scary, especially if you are older and already pregnant, but try not to worry too much. As discussed above, the risks for most of these complications that we’ve discussed are overall quite low. And as Dekker and colleagues write in the article on the Evidence Based Birth website, “The good news is that the vast majority of people 35 and older who make it to term will have a healthy baby.”

Abby Olena
Dr. Abby Olena has a PhD in Biological Sciences from Vanderbilt University. She lives with her husband and children in North Carolina, where she writes about science and parenting, produces a conversational podcast, and teaches prenatal yoga.

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