Can breastfeeding really prevent pregnancy?

Having a baby is an exciting and life-changing event. Yet it takes a lot of time and energy to care for infants, especially if you're juggling both family and work. So even the happiest and proudest parents might like to wait awhile after the birth of one child before welcoming another.

You may have heard that if you're breastfeeding, you won't get pregnant. However, that's not the full story. How well breastfeeding works as a form of birth control depends on several factors.

What to consider if you choose breastfeeding for birth control

Experts recommend waiting 18 months or more between pregnancies. This allows the uterus time to heal, and is safer for the birthing parent and infant.

There are many options for birth control. Some change the hormone cycles that rule periods and pregnancies. Nonhormonal options most often block or slow sperm, or prevent sperm and egg from meeting.

Breastfeeding is a natural birth control option that appeals to many people. Research shows it can be an effective method during the months when a woman is frequently breastfeeding and an infant is receiving only breast milk as food — no formula, baby foods, or other foods.

The medical term for this method is lactational amenorrhea method, or LAM. Lactational refers to breastfeeding, and amenorrhea means not having a period or regular menstrual cycle.

How does this method work?

Breastfeeding a baby regularly helps prevent ovulation, which is the release of an egg from the ovary. Ovulation must occur in order to conceive a pregnancy.

To successfully prevent pregnancy, all of these guidelines must be followed:

• Your baby is younger than 6 months and only breastfeeding (no formula or foods).
• You breastfeed at least every four hours during the day and every six hours overnight.
• You currently are not having periods (amenorrhea).

How effective is LAM?

Studies show that when used correctly as explained above, LAM can be about as effective as hormonal methods like the birth control pill. It is 98% effective in the first six months after the baby is born. This means that only two out of 100 people will get pregnant while using this method if the guidelines are followed correctly. If not, pregnancy is much more likely to occur. Your medical team can help you decide if this is a good birth control method for you right now and explain additional options.

What are the advantages of this method?

This form of birth control is completely natural and has no potential health risks or side effects. It is also free and does not require a medical appointment or procedure.

What are the disadvantages of this method?

• It's not practical or possible for everyone.
• You need to be able and willing to exclusively breastfeed your newborn. Giving your baby any amount of formula or other food decreases the effectiveness of this birth control method. It's also unclear whether pumping breast milk has the same effect as breastfeeding in preventing ovulation.
• It's temporary. Pediatricians recommend starting babies on some solid foods at around 6 months of age. Babies will also start sleeping for longer stretches at night.
• If you get your period while using this method, it is likely that you are ovulating again. That means you are not well protected against pregnancy, and could get pregnant unless you start using a different type of birth control.

If you decide to use LAM, be prepared to switch to a different method of birth control by the time your baby reaches 6 months, or before this if you're finding it impractical.

Is this method right for you?

This method could be a good choice temporarily if you are willing and able to

• breastfeed your baby exclusively for the first six months after birth — not mixing in formula or other foods
• nurse at least every four hours during the day and every six hours overnight.

This method doesn't protect against sexually transmitted infections (STIs), such as chlamydia or HIV. It's not a good choice for anyone who wishes to use a combination of breast milk and formula, or who has a health problem or uses medicines that could harm a baby if spread or passed through breast milk.

Choosing the right birth control for you

Birth control should suit your lifestyle and meet your health needs. Some people wish to avoid methods that contain any hormones, for example. Those with a history of blood clots or high blood pressure should avoid methods that contain estrogen. Busy people may do best with a 'set it and forget it' long-term method of birth control, such as an IUD or implant. And everyone who desires protection against STIs needs to think about using condoms with any birth control option they choose.

Share your preferences and needs with your midwife, doctor, or other members of your medical team. They can explain options and help you make a decision that works well for you.

See the Harvard Health Birth Control Center for more information on options.