Is Plan B (levonorgestrel) safe for use in breastfeeding mothers?

Plan B (Levonorgestrel) Safety During Breastfeeding

Plan B (levonorgestrel) is generally considered safe for use in breastfeeding mothers, with the advantages of using emergency contraception outweighing the theoretical risks to the breastfeeding infant. 1

Safety Profile and Recommendations

• Plan B contains levonorgestrel, a progestin-only emergency contraceptive that can be used as a single 1.5 mg dose or two 0.75 mg doses taken 12 hours apart 2
• For breastfeeding mothers, progestin-only contraceptives (like levonorgestrel) are classified as Category 2 in the US Medical Eligibility Criteria, meaning the advantages generally outweigh theoretical or proven risks 1
• Levonorgestrel passes into breast milk in small amounts, but the risk to the infant is considered minimal 3

Age-Related Considerations

• Research indicates that infants of different ages process levonorgestrel differently when exposed through breast milk: 3

  • 4-week-old infants: Cannot efficiently absorb or metabolize levonorgestrel
  • 12-week-old infants: Can metabolize levonorgestrel more efficiently than they absorb it
  • 24-week-old infants: Can both absorb and metabolize levonorgestrel efficiently

• Based on these findings, levonorgestrel is considered safer for use in mothers with infants 12 weeks or older 3

Practical Guidance

• If emergency contraception is needed while breastfeeding:

  • Take Plan B as soon as possible after unprotected intercourse (efficacy decreases with time) 2
  • Continue breastfeeding as normal - interruption is not necessary 1
  • Monitor the infant for any unusual symptoms, though adverse effects are rare 4, 5

• For ongoing contraception after using Plan B, consider discussing other progestin-only options that are compatible with breastfeeding 1

Important Considerations

• Plan B should be used as emergency contraception only and not as a regular contraceptive method 2
• The efficacy of Plan B is approximately 80% in preventing pregnancy when taken as directed 2
• Common side effects for the mother may include nausea, headache, breast tenderness, and temporary menstrual cycle changes 2

Clinical Context

• Most medications can be used safely during breastfeeding, and few drugs are absolutely contraindicated 5, 6
• When prescribing for breastfeeding mothers, the benefits of medication for the mother should be weighed against any potential risks to the infant 4
• Excessive caution often leads to unnecessary interruption of breastfeeding, which itself carries risks 5