Levonorgestrel Exposure During Pregnancy
If levonorgestrel emergency contraception is inadvertently taken during early pregnancy, neither the woman nor the fetus will be harmed, and the pregnancy can continue safely without intervention. 1, 2
Mechanism and Pregnancy Effects
Levonorgestrel emergency contraception works exclusively by preventing or delaying ovulation when taken before the preovulatory LH surge. 3, 4 The medication has no effect on an established pregnancy and does not disrupt implantation. 1, 2
- Levonorgestrel will not work if a woman is already pregnant because it acts before fertilization occurs, not after. 1
- Research demonstrates that when taken after ovulation has occurred (Days +1 to +2), levonorgestrel has little to no contraceptive effect, supporting that it does not interfere with post-fertilization events. 4
- There is no evidence for an anti-implantation effect despite this being frequently postulated. 3
Safety Data for Fetal Exposure
Children exposed to levonorgestrel during the conception cycle show no adverse effects on physical or mental development. 5
- A prospective cohort study of 195 children exposed to LNG-EC during their mothers' conception cycle compared to 214 unexposed controls found no significant differences in congenital malformations (2.1% vs 1.4%, p>0.05). 5
- Over 2 years of follow-up, there were no statistically significant differences in weight, height, head circumference, or intelligence scores between exposed and unexposed children. 5
- All developmental parameters in both groups were similar to national standards. 5
Clinical Management
No intervention is required when levonorgestrel emergency contraception is taken during early pregnancy. 1, 2
- The pregnancy should be managed as any other pregnancy without special monitoring or concern for teratogenic effects. 2
- Counsel the patient that inadvertent exposure poses no known risk to the developing fetus. 1, 2
- Standard prenatal care should proceed without modification. 5
Important Distinction: Levonorgestrel IUD During Pregnancy
The levonorgestrel-releasing intrauterine device is discussed in cardiovascular guidelines as a contraceptive option but is not addressed regarding pregnancy exposure in the provided evidence. 6 If a levonorgestrel IUD is in place when pregnancy occurs, this represents a different clinical scenario requiring device removal and pregnancy management per standard obstetric protocols.
Common Pitfalls to Avoid
- Do not confuse emergency contraception with medical abortion—levonorgestrel prevents pregnancy from starting but does not terminate an established pregnancy. 2
- Do not recommend pregnancy termination based solely on levonorgestrel exposure, as there is no teratogenic risk. 5
- Do not order additional fetal monitoring beyond routine prenatal care, as exposure does not increase risk of congenital anomalies. 5