Most women who breastfeed exclusively stop having menstrual periods. This is known as lactational amenorrhea. During lactational amenorrhea, the potential for ovulation is reduced. Subsequently, the chances of conception during this period decrease to approximately 0.5-2%, moreover, there is still a risk of pregnancy. Many women fear that because they are breastfeeding they cannot use any form of contraception. However, the use of contraception should not prevent a mother from breastfeeding.
Although most contraceptive methods are probably safe and should not put the infant at risk, some contraceptives can adversely affect milk supply and therefore should not be used by breastfeeding mothers. These include all estrogen containing products such as oral contraceptives, vaginal rings (i.e NuvaRing) and transdermal patches (Climara). We have no way to predict the outcome of breastfeeding once estrogen-containing birth control products are started. Some mothers may do fine and others can completely dry up. Therefore, if estrogen containing contraception is chosen, it is advised that women use the lowest estrogen dosage appropriate and monitor their milk supply. Mothers who have problems with milk production and those who are breastfeeding an older child (one year old or more) should be especially cautious.
Progesterone only pills are preferred as they are less likely to decrease milk supply. Some women, however, are sensitive to even progesterone only medications and therefore it is recommended they use the progesterone pills first rather than obtaining an injection of high dose progesterone (i.e Depo-Provera). This injection lasts 3 months and cannot be reversed once administered. If a breastfeeding mom does not have problems with milk supply after using progesterone only pills, then she can obtain the injection.
Barrier methods of birth control include diaphragms, condoms (male and female), spermicides, diaphragms, and cervical caps. These methods of contraception have no effect on milk production and therefore can be used without any concerns. However, their efficacy is inferior to other alternatives.
Finally, Intrauterine devices (IUD’s) should be used with caution. IUD’s can be hormonal or non-hormonal such as the copper containing type. The hormonal type contains progesterone. Progesterone doses in the IUD’s are low, however the impact of these blood levels on lactation have not been well investigated. Progestin containing IUD’s such as Mirena have been found to decrease milk supply in some women.