Effectiveness of the Progesterone-Only Birth Control Pill for Breastfeeding and Non-Breastfeeding Women
by Anne Eglash MD, IBCLC, FABM
Most physicians or other providers who work with postpartum women identify that the progesterone-only birth control pill (POP), aka the mini pill, is an appropriate birth control option because it is less likely to decrease milk production as compared to a combination oral contraceptive with estrogen (COC). However, according to the Centers for Disease Control Medical Eligibility Criteria, the COC is rated as generally safe for breastfeeding women starting at 6 weeks postpartum, with its advantage generally outweighing theoretical or proven risks.
In contrast, the World Health Organization medical eligibility criteria recommends not using the COC until 6 months for breastfeeding women, with a recommendation for follow up as needed.
Physicians often recommend a switch from the POP to the COC at some point during lactation to decrease the risk of pregnancy. The question is what do we know about the risk of pregnancy for breastfeeding women on the POP, and does it differ from non-breastfeeding women? Does it differ from the COC?
According to the authors of this week’s systematic review, the POP is now available without a prescription in UK pharmacies, and there is an initiative to submit an application to the US Food and Drug Administration to allow the over-the-counter sale of the POP. Therefore, the goal of the review was to explore the rate of pregnancy on the POP for breastfeeding and non-breastfeeding women, with anticipation that it may be available at some point in US pharmacies without a prescription.
The review identified 6 studies of 3184 women who were not breastfeeding, and 7 studies included 5445 women who were breastfeeding at some time. None of the 7 trials defined the degree or duration of breastfeeding.
Overall, this review found that the rate of pregnancy on the POP did not differ significantly between breastfeeding and non-breastfeeding women.
And, although the authors did not compare the rate of pregnancy with the POP vs the COC, they state in their introduction that research has not shown a difference in pregnancy rates between COC and POP users.
- For every 100 non-breastfeeding women, 2.2 became pregnant each year.
- For every 100 non-breastfeeding women, 5 became pregnant each year.
- For every 100 breastfeeding women, 0-4.9 became pregnant each year.
- For every 100 breastfeeding women 5-8% became pregnant each year.
See the Answer
To review published data on the effectiveness of a progestogen-only pill containing norgestrel 75 μg/day which should be under consideration by the FDA in 2022 for sale over the counter in the US.
A literature search in MEDLINE, EMBASE, and COCHRANE REVIEWS using specified search terms and adding related cross-references.
We identified a total of thirteen relevant studies of women using norgestrel 75 μg/day. None were reported with the rigor characteristic of trial reporting today. Nevertheless, six studies provided data on 3,184 women who were not breastfeeding, followed for over 35,000 months and reported a range of overall failure rates during typical use of norgestrel 75 μg/day from 0 to 2.4/hundred woman-years giving an aggregate Pearl Index of 2.2. Seven additional studies involved 5,445 women some of whom were breastfeeding for at least part of the period of follow-up. More than 36,000 months of use yielded 12-month life table cumulative pregnancy rates for norgestrel 75 μg/day ranging from 0 to 3.4. We were unable to calculate an aggregate Pearl Index for the breastfeeding studies because of lack of crucial data.
The data support that norgestrel 75 μg/day is highly effective in clinical use, with similar estimates of failure in breastfeeding and non-breastfeeding women, providing support to the case for approval without the need to see a healthcare provider.
In this study, the differences in pregnancy rates for breastfeeding vs non-breastfeeding women on the POP were not considered significantly different.
They state in their introduction that the failure rate of the POP is the same as the COC, with 9% of US women experiencing pregnancy in the first year of use if not used perfectly, and 0.3% with perfect use for either type of contraceptive tablet.
Based on this statement, breastfeeding women should not be coaxed into switching to the COC, unless they have an interest in lowering their milk production.
The authors discuss that the POP is considered a very safe form of birth control. Therefore, it would be a low risk medication for over-the-counter use, and certainly more effective than the barrier methods currently available over the counter, including condoms, the vaginal sponge, or spermicides.
The Centers for Disease Control Medical Eligibility Criteria list only 4 relative or strict contraindications to the POP, including breast cancer, liver cirrhosis, non-cancerous liver tumors, and ischemic heart disease.
If and when the POP is available over the counter in US pharmacies, it would be reasonable to advise breastfeeding women that the POP is a safe and effective form of contraception.