Key points
- Weight loss from GLP-1 medications can restore ovulation in women with obesity-related anovulation or PCOS, leading to unplanned pregnancies ("Ozempic babies")
- Semaglutide and tirzepatide must be stopped at least two months before a planned pregnancy — animal studies showed adverse foetal effects
- GLP-1 medications slow gastric emptying, which may reduce absorption of oral contraceptives — a non-oral method is recommended
- PCOS symptoms (irregular periods, excess androgens, insulin resistance) often improve significantly with GLP-1-induced weight loss
- Male fertility may also benefit from weight loss through improved testosterone and sperm parameters
The Ozempic babies phenomenon
In 2024 and 2025, reports of unplanned pregnancies among women taking GLP-1 receptor agonists became widely discussed in the media and on social media. The term "Ozempic babies" was coined to describe these unexpected conceptions, which appeared to be linked to the rapid weight loss achieved by semaglutide and tirzepatide.
The phenomenon is not caused by GLP-1 medications directly stimulating fertility. Rather, it is a consequence of weight loss restoring normal reproductive function in women whose fertility had been suppressed by obesity. Many of these women had been told they might struggle to conceive or had experienced years of irregular or absent periods.
Why does this happen?
Obesity disrupts the reproductive hormonal axis in several ways:
- Excess oestrogen: Fat tissue converts androgens to oestrogen through aromatisation. Elevated oestrogen levels disrupt the normal pulsatile release of gonadotrophin-releasing hormone (GnRH), which is required for ovulation.
- Insulin resistance: High insulin levels stimulate the ovaries to produce excess androgens, which inhibit follicle development and ovulation. This is the central mechanism in PCOS.
- Leptin dysregulation: Obesity causes leptin resistance, which disrupts the hypothalamic-pituitary-ovarian axis and suppresses luteinising hormone (LH) pulsatility.
- Chronic inflammation: Obesity-related inflammation affects ovarian function and egg quality.
When significant weight loss occurs — even 5 to 10 per cent of body weight — these hormonal disruptions begin to normalise. Ovulation can resume quickly, sometimes within weeks, before the woman realises her fertility has returned.
Critical safety message: Semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) are contraindicated in pregnancy. The MHRA advises stopping these medications at least two months before a planned pregnancy. If you discover you are pregnant while taking a GLP-1 medication, stop the medication immediately and contact your GP or midwife.
PCOS and GLP-1 therapy
Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age, affecting approximately 1 in 10 women in the UK. It is characterised by irregular or absent periods, excess androgen production (causing acne and excess hair growth) and polycystic ovaries on ultrasound.
Insulin resistance is a core feature of PCOS, present in approximately 70 to 80 per cent of affected women, regardless of BMI. However, obesity significantly worsens insulin resistance and the severity of PCOS symptoms.
How weight loss helps PCOS
Weight loss of 5 to 10 per cent has been shown to:
- Restore regular ovulatory cycles in up to 50 to 60 per cent of anovulatory women with PCOS
- Reduce serum testosterone and free androgen index by 20 to 30 per cent
- Improve insulin sensitivity by 30 to 50 per cent
- Reduce hirsutism and acne severity
- Improve pregnancy rates both naturally and with assisted reproduction
Clinical evidence
Several studies have specifically examined GLP-1 receptor agonists in women with PCOS. A systematic review and meta-analysis published in the Journal of Clinical Endocrinology and Metabolism found that GLP-1 RA therapy in women with PCOS resulted in significant improvements in body weight, BMI, waist circumference, insulin resistance (HOMA-IR), testosterone levels and menstrual regularity compared with placebo or metformin alone.
While GLP-1 medications are not yet specifically licensed for PCOS in the UK, NICE guidance on fertility treatment recognises that weight loss is a first-line recommendation for overweight women with PCOS who wish to conceive.
PCOS and fertility planning: If you have PCOS and are taking a GLP-1 medication to lose weight before trying to conceive, work closely with your GP or fertility specialist. The ideal approach is to achieve your target weight, stop the GLP-1 medication for at least two months, and then begin trying to conceive with your hormonal function restored.
Contraception considerations
Women of childbearing age taking GLP-1 medications should use reliable contraception throughout treatment and for at least two months after stopping, in line with MHRA and manufacturer guidance.
Oral contraceptive absorption
GLP-1 receptor agonists slow gastric emptying as part of their mechanism of action. This can reduce the rate and extent of absorption of oral medications, including the combined oral contraceptive pill (COCP) and the progestogen-only pill (POP). The clinical significance of this interaction is still being studied, but the MHRA and prescribing information recommend caution.
Recommended contraceptive options
| Contraceptive method | Affected by GLP-1? | Suitability |
|---|---|---|
| Combined oral pill | Potentially — slower absorption | Use additional barrier method or switch |
| Progestogen-only pill | Potentially — slower absorption | Use additional barrier method or switch |
| Hormonal implant (Nexplanon) | No — not absorbed orally | Excellent choice |
| IUS (Mirena, Kyleena) | No — acts locally | Excellent choice |
| Copper IUD | No — non-hormonal | Excellent choice |
| Injectable (Depo-Provera) | No — not absorbed orally | Suitable (note weight gain risk) |
| Contraceptive patch | No — transdermal absorption | Suitable |
| Condoms | No | Suitable as primary or backup method |
Practical advice: If you are currently taking an oral contraceptive and begin a GLP-1 medication, discuss your contraception with your GP or pharmacist. A switch to a long-acting reversible contraceptive (LARC) such as an implant or IUS eliminates any concern about absorption interactions.
Male fertility and GLP-1 medications
Obesity has well-documented negative effects on male fertility. Excess body fat disrupts the hypothalamic-pituitary-gonadal axis in men, leading to:
- Lower testosterone: Aromatisation of testosterone to oestradiol in fat tissue reduces circulating testosterone levels. Obesity-related hypogonadism is common in men with BMI above 30.
- Reduced sperm count and motility: Multiple studies have shown that obesity is associated with lower sperm concentration, reduced total motile sperm count and increased DNA fragmentation.
- Erectile dysfunction: Both vascular dysfunction and low testosterone contribute to higher rates of erectile dysfunction in obese men.
Weight loss of 10 per cent or more has been shown to increase testosterone levels by 2 to 3 nmol/L on average and improve semen parameters. There is currently no evidence that semaglutide or tirzepatide directly harm male reproductive function. Animal studies in male rats have shown some effects on spermatogenesis at very high doses, but the relevance to human therapeutic doses is uncertain.
Pregnancy safety: what we know
GLP-1 receptor agonists are classified as contraindicated in pregnancy by the MHRA. This classification is based primarily on animal data, as ethical constraints mean there are no randomised controlled trials of these medications in pregnant women.
Animal data
Animal reproductive toxicology studies for semaglutide showed adverse effects including reduced foetal growth, skeletal abnormalities and increased embryonic loss at doses comparable to or above therapeutic human exposure. Similar findings have been reported for tirzepatide and liraglutide.
Human data
Observational data from women who became pregnant while taking GLP-1 medications is accumulating but remains limited. The existing evidence from pregnancy registries and case series has not identified a clear pattern of birth defects, but the sample sizes are too small to draw definitive conclusions. This is why the precautionary approach — stopping the medication before conception — remains standard practice.
The two-month washout period
The MHRA recommends stopping semaglutide at least two months before a planned pregnancy. This allows the drug to be fully eliminated from the body. Semaglutide has a half-life of approximately one week, so after five half-lives (approximately five weeks) the drug is essentially cleared. The two-month recommendation provides an additional safety margin.
Planning pregnancy after GLP-1 therapy
For women who have used GLP-1 medications for weight loss and are now planning a pregnancy, a structured approach is recommended:
- Achieve target weight: Work with your GP or weight management service to reach a healthy BMI before stopping the medication
- Stop the GLP-1 medication: At least two months before attempting to conceive
- Start folic acid: Begin taking 400 micrograms of folic acid daily (or 5 mg if BMI remains above 30) at least three months before conception
- Maintain weight: Focus on dietary habits and exercise routines established during treatment to prevent regain
- Pre-conception counselling: See your GP for a pre-conception check, particularly if you have PCOS, diabetes or other metabolic conditions
- Monitor for weight regain: Some weight regain after stopping GLP-1 therapy is common; discuss strategies with your healthcare team