GLP-1s and Pregnancy: What a New Study Adds, and What It Can't Tell You
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If you're on a GLP-1 and might get pregnant, the advice you've heard is probably "stop first." That advice isn't wrong. But it rests on less science than most people assume. A new review out late last month adds real data for the first time that might be the first step to understanding the risks associated with taking a GLP-1 while pregnant. We'll walk through what it found, who it applies to, and what's still unknown.
Who This Helps
This is for you if you take a GLP-1 and are planning a pregnancy, or just found out you're pregnant. It's also for partners and family trying to understand the warnings. We don't give medical advice here. We explain what the evidence says so you can have a better talk with your doctor.
First, who the new study is about
The study came out in a Lancet journal on September 29 (The Lancet). It looked at women with diabetes. Type 1, type 2, or the kind that starts in pregnancy. It did not study women on a GLP-1 for weight alone.
Women with diabetes have higher pregnancy risks to begin with. So the findings tell us the most about them. They tell us less about someone with no diabetes who is on Wegovy or Zepbound for weight.
What it found
The team pooled seven studies. Together they covered more than 43,000 women who took a GLP-1 around the time they got pregnant. Most of the exposure was in the first three months (King's College London).
For most outcomes, they found no clear link. Birth defects were not more common in women who stopped the drug in the first three months. Early birth, high blood pressure, stillbirth, newborn deaths, small babies and C-sections all showed no clear link either.
One outside expert, Dr. Nerys Astbury at Oxford, read it more cautiously. She said the ranges around every one of those results are wide enough to include no effect, but also some harm or some benefit. There were few studies and they varied a lot. She said the conclusions go beyond what the evidence can support (Science Media Centre).
One number stood out. Early pregnancy loss was 31% more common in the GLP-1 group. But the authors say to be careful with this. Almost all of it came from one study. And that study lumped miscarriage together with women who chose to end a pregnancy, which are very different things. And as Dr. Astbury noted, the range of likely values includes no effect at all.
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What the authors themselves say
They're blunt about the limits. Their words: "current evidence is insufficient to define the benefits and risks of GLP-1RA therapy across the reproductive life course." They call for large studies that follow women and babies over time.
They also asked a panel of 42 experts and 60 women who'd been through it. The panel backed using GLP-1s to get healthy before pregnancy, mainly for type 2 diabetes. But they also said to stop before a planned pregnancy. The Wegovy label says the same, with a two-month gap.
Why the labels say to stop
The Wegovy label says to stop at least two months before trying to get pregnant. The reason it gives is how long the drug lasts. Semaglutide stays in your body five to seven weeks after the last dose. Two months is a safety margin on top of that (Wegovy prescribing information).
The warning about harm to a baby comes from animal tests. Rats, rabbits and monkeys given the drug lost more pregnancies and had more birth defects. The label notes that in rabbits and monkeys, this happened alongside big drops in the mothers' weight. The label also says plainly that weight loss offers no benefit to a pregnant patient (Wegovy prescribing information).
Tirzepatide, the drug in Zepbound and Mounjaro, has no set wait time on its US label. Its half-life is about five days, so it leaves the body faster than semaglutide. The label still says to stop once you know you're pregnant (Zepbound prescribing information). Same for Foundayo, the new pill.
What earlier studies found
This isn't the first look. A study across several countries followed 938 pregnancies in women with type 2 diabetes who took a GLP-1. Birth defects were about as common as with insulin, though the range left room for a small increase (JAMA Internal Medicine).
A US study this June compared about 3,500 women who kept taking a GLP-1 into early pregnancy with those who stopped. Pregnancies that didn't end in a live birth were slightly more common in the group that kept taking it, 29.7% versus 27.1%, but the range included no difference. The authors called their results imprecise and said they couldn't rule out real differences either way (Annals of Internal Medicine).
And a review this month pooled ten studies with over two million pregnancies. About 8,300 of those women took a GLP-1 in the six months before. It found no clear rise in any bad outcome (City St George's). Again, the authors said this is not proof of safety.
So the pattern is steady. Study after study looks and doesn't find a problem. But none is big enough or careful enough to say the drugs are safe.
The other way pregnancy comes up
Some people get pregnant on a GLP-1 without planning to. There are two reasons this happens that are specific to those taking GLP-1s.
First, losing weight can bring back regular cycles. This is well known in women with PCOS. A review of 11 trials with 840 women found those with PCOS on a GLP-1 were 72% more likely to get pregnant without fertility treatment (BMC Endocrine Disorders). Total pregnancy rates, counting IVF, were no different.
Second, tirzepatide can make the pill work less well. The Zepbound and Mounjaro labels say to switch to a non-pill method, or add a barrier method, for four weeks after starting and after each dose increase. We explain that in our piece on pills and backup. An Australian study of 18,000 women starting a GLP-1 found only about one in five had a highly effective form of birth control on record (Medical Journal of Australia).
What's still unknown
- Anything past the first three months. Almost all the data is from the first three months.
- Miscarriage on its own. Studies keep mixing it in with women who chose to end a pregnancy or those who lost the pregnancy due to other reasons.
- How the kids do later. The review authors list this as a gap.
- The right washout for tirzepatide. The US label doesn't give one.
- Whether stopping has its own risks. Weight tends to come back, and in diabetes blood sugar can swing. The review doesn't weigh that against the drug.
Final Takeaway
The new study is cautious good news. In women with diabetes who stopped a GLP-1 early in pregnancy, birth defects were not more common. Most other outcomes showed no clear link either, though an outside expert warns the ranges are wide. One study hinted at more early loss, but it mixed two things together. The drug labels still say to stop before trying, and the expert panel agrees. If you're planning a pregnancy, that talk with your doctor is the one that counts.
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Frequently Asked Questions
Does this study mean GLP-1s are safe in pregnancy?
No. It found no clear link to most problems in women with diabetes. The authors say the evidence isn't strong enough to call the drugs safe or unsafe, and an outside expert says the ranges are too wide to be sure either way.
How long before trying should I stop?
The Wegovy label says at least two months, and Ozempic carries the same drug. Zepbound and Mounjaro don't give a number. Your doctor can tell you what fits your situation.
What if I got pregnant while on one?
The labels say to stop once you know, so tell your doctor right away. So far, studies of women who stopped early haven't found more birth defects. That's good news, though it isn't proof.
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Lauren PescarusLauren Pescarus is a team member with GLP Winner where she works on marketing, content creation, and operations. She has over 10 years experience in the content creation space, including in the GLP-1 space where she works to stay on top of access news, research updates, and lifestyle tips guided by science.