A: Potentially, yes! Semaglutide (Ozempic and Wegovy) and tirzepatide (Mounjaro and Zepbound) may reduce birth control effectiveness and may increase risk of birth defects if taken during pregnancy.
The new GLP-1 receptor agonist drugs have been a breakthrough in treating obesity and Type 2 diabetes. They significantly improve blood glucose levels and lower body weight. Therefore, use of these medications has increased dramatically. Unfortunately, these drugs may have negative effects on birth control and on pregnancies. More studies are needed. In the meantime, patients and clinicians need to be aware of the potential risks.
Possible decreased effectiveness of hormonal birth control
Tirzepatide (Mounjaro and Zepbound) was shown in clinical trials to reduce birth control pill blood levels by 20-60% when given as an initial single dose. The reasons for this change in blood levels and its impact on protection are not entirely clear. It may be due to slower stomach emptying. There are no data for birth control pill levels with continued use of tirzepatide or for non-pill types of birth control (e.g. patch, ring, implant, injection, or IUD). The package labeling suggests the drug interaction is only a problem with the initial dose of tirzepatide and with future dose increases (based on data on acetaminophen levels). It recommends using a barrier method of birth control (e.g. condoms) for 4 weeks after first starting and for 4 weeks after each dose increase.
To date, studies of semaglutide (Ozempic and Wegovy) only reported birth control pill blood levels from patients who were on a regular, stable dose of semaglutide. In these people, birth control pill levels were unaffected. The studies did not report on levels when first starting or increasing the dose of semaglutide nor with non-pill types of birth control. The package insert does not contain any warning about interaction with birth control, but this does not necessarily mean that it’s risk-free.
There are some anecdotal reports of unintended pregnancies in patients taking semaglutide who were using pills and other methods (e.g. patch or ring) for birth control. It is not known whether this was due to the semaglutide or some other factor.
Overall, there are not enough data yet to know for sure how these medications affect hormonal forms of birth control. They may only affect pills and only at starting and dosage increases, but the data are sparse. We don’t really know yet. We need more research!
We also do not know the impact of these medications on a person’s ability to get pregnant if they’re not taking birth control. It is possible that it could increase, decrease, or be unchanged.
Risk of miscarriage and birth defects
Both semaglutide and tirzepatide have been shown to cause miscarriage and birth defects in pregnant lab animals (rats and rabbits) at doses equivalent to what is used for humans. It is not clear whether this is due to the drugs themselves or the weight loss that they cause. The drugs stay in the system a long time, about 4-6 weeks, after the last dose. Therefore, the package labeling for semaglutide advises that both men and women who are planning a pregnancy discontinue the medication for **two months** before trying for a pregnancy. The tirzepatide package insert has only a generic warning that the drug may cause fetal harm. A study to assess pregnancy outcomes in humans is currently underway for Wegovy (semaglutide), but we have no data on it yet.
Overall, the new weight loss medications hold a lot of promise for treating diabetes and obesity. BUT people who can get pregnant need to be careful. These medications are associated with birth defects in animals, and we’re not really sure yet how they affect birth control and fertility. If you’re someone who could get pregnant, make sure you discuss this with your clinician.
Stay safe, stay well.
Those Nerdy Girls