Why you shouldn’t use GLP-1 during pregnancy. How it can affect you and your baby

What is GLP-1 and why is it used for weight management?

GLP-1 is a hormone your body produces naturally. It helps regulate appetite, fullness and blood sugar levels. Medicines that mimic GLP-1 are used to treat overweight, obesity and type 2 diabetes.

You might recognise names like:

• Ozempic and Wegovy, which contain semaglutide
• Mounjaro, which contains tirzepatide

These treatments work by reducing hunger, helping you feel full for longer and slowing down how quickly your stomach empties. That can make it easier to eat less and lose weight, especially alongside lifestyle support.

Side effects and possible complications

If you’re starting GLP-1 treatment, it’s important to know about potential side effects. The most common ones include:

• Nausea
• Constipation
• Diarrhoea
• Stomach pain

For some people, these symptoms can affect day-to-day life, especially at the beginning.

In rarer cases, there may be a higher risk of more serious complications, such as gallbladder problems or inflammation of the pancreas. That’s why it’s important to talk things through with a doctor before starting treatment.

GLP-1 medicines can also influence your risk of certain health conditions, not just type 2 diabetes and obesity. Being well informed about both common and uncommon side effects helps you make a decision that feels right and know when to seek medical advice.

Why pregnancy is a particularly sensitive time

During pregnancy, both you and your baby are affected by major hormonal and metabolic changes. In the first few weeks, vital organs form and the nervous system develops. That’s why only treatments that are well studied and considered safe in pregnancy are recommended.

When it comes to GLP-1 medicines, research in pregnant women is very limited. People who are pregnant are usually not included in clinical drug trials. Most of what we know comes from animal studies, small case reports and registry data, rather than large clinical studies in humans.

Can you use GLP-1 during pregnancy?

In short, no. GLP-1 medicines are not recommended during pregnancy. This applies to semaglutide, tirzepatide and other medicines in the same group.

The reason is simple: there isn’t enough evidence to confirm that they’re safe for a developing baby. When it comes to pregnancy, the safety bar is very high. If a risk can’t be ruled out, the treatment isn’t recommended.

Official prescribing information states that GLP-1 treatment should be stopped before pregnancy and not started if you’re already pregnant.

What does the research say?

There are no large clinical studies looking at GLP-1 as a weight treatment during pregnancy.

The research we do have includes:

• Animal studies, which have shown reproductive toxicity with some GLP-1 medicines at doses that affected fetal development. This is one of the main reasons for caution.
• Registry and observational data, where some individuals became pregnant while on treatment. However, these data are still limited and not strong enough to confirm safety or fully understand potential risks.

Overall, the evidence isn’t sufficient to confirm safety in pregnancy. For that reason, GLP-1 receptor agonists are generally not recommended, and product information states that treatment should be stopped if you’re planning a pregnancy or become pregnant.

What if you become pregnant while taking Ozempic, Wegovy or Mounjaro?

If you’ve been using Ozempic, Wegovy or Mounjaro and then find out you’re pregnant, the general advice is to stop the treatment and contact your doctor as soon as possible.

Your situation should always be assessed individually. Your doctor can review your health, discuss any potential risks and plan appropriate follow-up if needed.

How long should you wait before trying to conceive?

If you’re planning to become pregnant, it’s important to stop GLP-1 treatment in good time. Some of these medicines stay in the body for several weeks after the last dose.

• For semaglutide medicines such as Ozempic and Wegovy, it’s usually recommended to stop at least two months before trying to conceive.
• For tirzepatide (Mounjaro), a gap of at least one month is generally advised.

Always plan this together with your doctor. This is especially important if you’re using the medicine to manage type 2 diabetes, as your blood sugar levels may need close monitoring and adjustment when treatment changes.

Why GLP-1 isn’t suitable during pregnancy from a nutrition point of view

Beyond the uncertainty around safety for your baby, there are practical reasons too.

GLP-1 reduces appetite and can cause nausea. During pregnancy, your body needs steady and adequate nutrition to support your baby’s development. Nausea is already common in early pregnancy, and further appetite suppression could make it harder to meet your nutritional needs.

During pregnancy, the goal isn’t weight loss. It’s supporting a healthy pregnancy.

What about overweight during pregnancy?

It’s common to have questions about weight during pregnancy. Living with overweight or obesity can be linked to a higher risk of certain complications, but that doesn’t mean you should try to lose weight with medication while pregnant.

Instead, the focus is on creating the best possible conditions for a healthy pregnancy through safe and sustainable habits. That means supporting both your needs and your baby’s, rather than focusing on weight itself.

General advice in the UK often includes:

• Regular meals with balanced, nourishing food
• Physical activity adapted to your pregnancy and individual circumstances
• Stable blood sugar levels, enough rest and good sleep
• Ongoing support and check-ins with your midwife and maternity team

For some people, extra support with nutrition, blood sugar or lifestyle habits can be especially important. This is always tailored to your pregnancy, with the aim of supporting both you and your baby.

GLP-1 after pregnancy and breastfeeding

After you’ve given birth, and once breastfeeding has completely stopped, GLP-1 treatment may be an option again.

The timing and approach should always be planned individually with your doctor. A full review will usually look at your current health, weight changes, any medical conditions and your personal goals.

GLP-1 medicines are not recommended while breastfeeding, so treatment would only be considered once breastfeeding has ended.

The aim is to make sure that any restart is safe, well considered and suited to your life after pregnancy.

At Yazen, this is done with personalised support. The goal isn’t just weight loss, but long-term health, safe follow-up and a plan that works in everyday life, even with a baby at home.

Summary

GLP-1 medicines such as Ozempic, Wegovy and Mounjaro can be effective treatments for overweight and obesity. However, they are not recommended during pregnancy.

The main reason is that scientific evidence is limited, and safety for the developing baby cannot be confirmed.

If you’re planning a pregnancy, GLP-1 treatment should be stopped well in advance. If you become pregnant while on treatment, you should stop the medicine and contact your doctor for personalised advice and follow-up.

During pregnancy, the focus shifts to healthy habits and supportive care through NHS maternity services. After pregnancy, and once breastfeeding has ended, GLP-1 treatment can be considered again following an individual medical review.

Common questions about GLP-1 and pregnancy

Can I use GLP-1 treatment if I’m pregnant?
No. GLP-1 medicines are not recommended during pregnancy because there isn’t enough evidence to confirm they are safe for a developing baby. The focus should instead be on well-established, pregnancy-safe approaches.

What should I do if I’m on GLP-1 treatment and want to become pregnant?

If you’re using GLP-1 and planning a pregnancy:

• Speak to your doctor early
  Let them know about your plans so you can agree when to stop treatment and how to monitor your health.
• Stop treatment within the recommended timeframe
  Different medicines stay in the body for different lengths of time, so the gap between stopping treatment and trying to conceive will depend on which one you’re using.
• Use contraception until the recommended gap has passed
  This helps avoid unintentional exposure in very early pregnancy.
• Consider folic acid before pregnancy
  Folic acid is usually recommended before and during early pregnancy. After weight loss, some people may have lower folate levels. Your doctor can advise on the right dose for you.

What if I become pregnant while using Ozempic or Wegovy?
Contact your doctor as soon as possible for individual advice and follow-up.

Can GLP-1 affect my baby’s development?
We currently have limited data in humans. Animal studies have shown signs of reproductive toxicity with some GLP-1 medicines, particularly at doses that affected fetal growth and development. Because robust human data are lacking, a precautionary approach is taken.

What side effects can I get from GLP-1 treatment?
The most common are nausea, constipation, diarrhoea and stomach pain. More serious complications are possible but uncommon.

Are there alternative treatments for overweight and type 2 diabetes during pregnancy?
Yes. During pregnancy, other approaches that are better studied and considered safe may be used. This can include dietary support, adapted physical activity and, if needed, other medicines with established safety in pregnancy. Treatment is always tailored to you.

Can I start GLP-1 after pregnancy and breastfeeding?
Yes, treatment may be considered once breastfeeding has finished and after an individual medical review.

Why is steady nutrition important during pregnancy?
Your body needs extra nutrients to support your baby’s development. Because GLP-1 can reduce appetite and cause nausea, it may make it harder to get enough nutrition during pregnancy.

Sources

1. American Journal of Obstetrics and Gynecology. Glucagon-like peptide-1 receptor agonist use in pregnancy: a review. https://doi.org/10.1016/j.ajog.2024.08.024
2. The New England Journal of Medicine. Once-Weekly Semaglutide in Adults with Overweight or Obesity. https://www.nejm.org/doi/full/10.1056/NEJMoa2032183
3. The New England Journal of Medicine. Tirzepatide Once Weekly for the Treatment of Obesity.
   https://www.nejm.org/doi/full/10.1056/NEJMoa2206038
4. European Medicines Agency. Wegovy (semaglutide) product information. https://www.ema.europa.eu/en/medicines/human/EPAR/wegovy
5. European Medicines Agency. Mounjaro (tirzepatide) prescribing information. https://www.ema.europa.eu/en/medicines/human/EPAR/mounjaro‍

For more information about appetite regulation and managing hunger, visit Yazen.

There are different treatment options available, and it’s always worth discussing them with a doctor or healthcare professional. Research into GLP-1 and other obesity treatments is evolving quickly. Staying informed can help you make confident, well-informed decisions about your health.

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