Breastfeeding as Contraception
Breastfeeding can prevent pregnancy, but only under very specific conditions: the mother must be exclusively or nearly exclusively breastfeeding, remain amenorrheic (no menstrual periods), and be less than 6 months postpartum—all three criteria must be met simultaneously for approximately 98% effectiveness. 1
The Lactational Amenorrhea Method (LAM)
The CDC's U.S. Medical Eligibility Criteria establishes that LAM provides reliable contraceptive protection when all three of the following conditions are present 1:
- Amenorrhea (no menstrual bleeding has returned)
- Fully or nearly fully breastfeeding (at least 85% of feeds are breast milk, with minimal supplementation)
- Less than 6 months postpartum
When these criteria are met, the pregnancy risk is approximately 2% over 6 months, which compares favorably to typical use of condoms (18% failure rate) or birth control pills (9% failure rate) 1, 2, 3.
Why LAM Works
Frequent suckling suppresses gonadotropin-releasing hormone, luteinizing hormone, and follicle-stimulating hormone through an opioid pathway involving beta-endorphins, which maintains amenorrhea and prevents ovulation 2. However, this suppression is highly dependent on breastfeeding intensity and frequency—reduced suckling precipitates the return of ovulation 2.
Critical Limitations and When Protection Ends
LAM protection ends immediately when any of the three criteria are no longer met 1, 4:
- Once menstruation returns, fertility can resume even while breastfeeding continues 3, 5
- After 6 months postpartum, ovarian function resumes regardless of breastfeeding intensity 5
- Introduction of supplemental feeding reduces the contraceptive effect 1
The CDC explicitly categorizes fertility awareness-based methods during breastfeeding as Category D (delay) for the first 6 weeks postpartum because women are unlikely to have detectable fertility signs, but emphasizes that "the likelihood of resumption of fertility increases with time postpartum and with substitution of breast milk with other foods" 1, 4.
Common Pitfalls to Avoid
Do not rely on breastfeeding alone without meeting all three LAM criteria 1. Research shows that only 8% of U.S. pregnant women understand that exclusive breastfeeding significantly reduces pregnancy risk, and only 2% recognize it as more effective than typical contraceptive use 6. This knowledge gap leads to unintended pregnancies.
Women with conditions that make pregnancy an unacceptable health risk should not rely on LAM due to its relatively higher typical-use failure rates compared to long-acting reversible contraception 1.
Transition to Other Contraceptive Methods
Alternative contraception must be initiated as soon as any LAM criterion is no longer met 1, 2. The most appropriate options for breastfeeding women include 1, 4, 7:
- Progestin-only methods (pills, implants, DMPA injections) can be started immediately postpartum with no negative effects on milk production or infant health 1, 4, 7
- IUDs (copper or levonorgestrel) can be inserted immediately postpartum 1, 4, 7
- Combined hormonal contraceptives should be avoided until at least 6 weeks postpartum due to potential reduction in milk supply 4, 7
Real-World Effectiveness Considerations
While LAM demonstrates 98% effectiveness under ideal conditions 2, research from well-nourished Australian women showed that extending LAM beyond 6 months while maintaining amenorrhea resulted in only 7% pregnancy rates by 12 months 3. However, all women eventually resumed ovulation while still breastfeeding, emphasizing that breastfeeding alone without amenorrhea is not reliable contraception 3, 5.
The critical clinical message: LAM is highly effective contraception for up to 6 months postpartum, but only when all three criteria are strictly maintained, and it must be replaced with another contraceptive method as soon as any criterion is no longer met 1, 2.