Semaglutide & Pregnancy UK: Safety, Washout Period & MHRA Guidance

Semaglutide is absolutely contraindicated during pregnancy. This applies to all semaglutide-containing products licensed in the UK: Ozempic (0.5–2 mg injectable), Wegovy (2.4 mg injectable), and Rybelsus (oral semaglutide for diabetes).

The basis for this contraindication comes from:

Animal reproductive studies: - Studies in rats and rabbits at doses producing exposures lower than those achieved at the maximum recommended human dose showed increased rates of early embryonic deaths, skeletal malformations and other foetal abnormalities - These findings triggered the standard regulatory contraindication that applies to all drugs with foetotoxic signals in animal data until proven safe in human pregnancy

Mechanism-based concerns: - GLP-1 receptors are expressed in foetal tissue; the potential for developmental disruption from pharmacological GLP-1 agonism during organogenesis is a theoretical concern - Significant weight loss during pregnancy is independently associated with adverse foetal outcomes including growth restriction

Absence of human safety data: - No controlled studies have been conducted in pregnant women for semaglutide; the contraindication reflects precautionary principle in the absence of safety evidence, not a documented human teratogenic signal - Post-marketing pregnancy registries for semaglutide are ongoing; data to date is limited and primarily from inadvertent exposures

The MHRA's position, reflected in the semaglutide SmPC, is unequivocal: do not use semaglutide during pregnancy. If pregnancy is detected during treatment, discontinue immediately.

One of the most practically important aspects of semaglutide use for women of childbearing age is the recommended pre-conception washout period — the time between stopping semaglutide and attempting to conceive.

MHRA and SmPC recommendation: The Wegovy and Ozempic SmPCs state that semaglutide should be discontinued at least 2 months before a planned pregnancy, due to the long half-life of the drug.

Pharmacokinetic basis: - Semaglutide has an exceptionally long half-life of approximately 1 week, which is one of the reasons it can be given as a once-weekly injection - Following the last dose, it takes approximately 4–5 half-lives (approximately 5 weeks) for most of the drug to be cleared from the body - The 2-month washout recommendation provides a safety buffer beyond the simple pharmacokinetic clearance to ensure negligible drug exposure at the time of conception and early embryonic development - This 2-month period applies regardless of the dose being taken

Practical implications: - Women planning a pregnancy should discuss a stopping plan with their prescriber well in advance — ideally at least 3 months before planned conception to allow the 2-month washout plus some flexibility - Effective contraception is essential during semaglutide treatment for women of childbearing age — this should be discussed at initiation - Women who become pregnant unexpectedly while taking semaglutide should stop the medication immediately and inform their midwife and GP — the prescribing team should also be notified to support a transition plan

Obesity itself is well established as a cause of reduced fertility in both men and women, through mechanisms including hormonal dysregulation, insulin resistance, and chronic inflammation. GLP-1 medications' effects on fertility are therefore complex to interpret — because substantial weight loss may improve fertility even as the drug itself carries a pregnancy contraindication.

Potential positive effects on fertility (through weight loss): - Weight loss in women with polycystic ovary syndrome (PCOS) — a condition strongly associated with obesity and a common cause of infertility — is associated with restoration of menstrual regularity and ovulation - Improvements in insulin sensitivity from GLP-1-induced weight loss may support fertility in women with insulin-resistant PCOS - In men, obesity-related hypogonadism (low testosterone, reduced sperm quality) may improve with significant weight loss

Direct effects of semaglutide on reproductive hormones: - Clinical trials have shown that semaglutide treatment can result in resumption of regular menstrual cycles in previously anovulatory women — a welcome effect, but one with an important implication: women who believed they were infertile due to obesity-related anovulation may become fertile during treatment - This represents a genuine pregnancy risk if contraception is not used consistently

Practical implication: UK prescribers initiating GLP-1 therapy in pre-menopausal women should explicitly discuss the possibility that fertility may improve during treatment, and ensure that effective contraception is in place regardless of prior fertility history. This is a nuance that is sometimes missed in clinical practice.

The question of whether semaglutide is safe during breastfeeding is separate from the pregnancy question — the pharmacokinetics and exposure routes differ substantially.

MHRA and SmPC position: The semaglutide SmPC states that it is unknown whether semaglutide is excreted in human breast milk. Based on studies in animals showing semaglutide transfer into milk, breastfeeding is not recommended during treatment.

Pharmacological considerations: - Semaglutide is a large peptide molecule; peptide drugs typically have low oral bioavailability when ingested (they are broken down in the gastrointestinal tract) - Even if some semaglutide were transferred into breast milk, systemic exposure in the infant would likely be very low due to peptide degradation during digestion - However, because GLP-1 receptors are expressed in developing tissues, and because the precautionary principle applies in the absence of robust infant safety data, the recommendation is to avoid breastfeeding during treatment

Practical guidance for UK women: - Women who are breastfeeding and wish to start GLP-1 therapy for weight management should wait until weaning is complete - For women who become pregnant unexpectedly and stop semaglutide (as required), they may breastfeed after birth without restriction — the 2-month washout will have elapsed during pregnancy - If there is clinical urgency for resuming semaglutide (e.g., in a patient with type 2 diabetes), the benefit-risk balance and timing of weaning should be discussed with an endocrinologist and neonatologist

For UK women of childbearing age using semaglutide for weight management or diabetes, a clear plan for managing the interaction with reproductive life is essential.

If you are currently using semaglutide and considering pregnancy: 1. Do not stop contraception without speaking to your prescriber first 2. Plan your stop date — aim to stop semaglutide at least 2 months before you want to start trying to conceive 3. During the washout period, maintain the dietary and lifestyle habits established during treatment to minimise weight regain 4. Inform your GP that you are in a pre-conception washout phase — they can offer pre-conception health support including folic acid supplementation 5. If you have type 2 diabetes and semaglutide is your primary glucose-lowering medication, your GP or diabetologist will need to arrange an alternative treatment plan before you stop

Monitoring during the post-washout period: - Weight management during the washout and early pregnancy may be challenging; evidence-based, pregnancy-safe approaches (dietary modification, appropriate physical activity) should be supported by your care team - Women who gained significant weight after stopping GLP-1 therapy and before pregnancy should discuss timing and weight targets with their GP or obstetric team

If you discover you are pregnant while taking semaglutide: 1. Stop the medication immediately 2. Contact your GP or midwife as soon as possible 3. Do not panic — the absolute risk of harm from inadvertent early exposure is uncertain, but animal data reflects higher-than-human doses 4. Register with antenatal services promptly for appropriate monitoring

*This article is for informational purposes only. Always consult your GP, prescriber or obstetrician before making any decisions about medication during pregnancy or while trying to conceive.*