How safe is breastfeeding as a form of birth control?

Although breastfeeding can work well as a method of birth control, like any other type of contraceptive, it’s not foolproof.

Breastfeeding delays the return of your periods. But you'll ovulate before you have your first period. So there's a chance you could become pregnant if you rely on your period returning as a sign that you’re fertile again.

Frequent and regular breastfeeding as a form of contraception is called the lactational amenorrhoea method (LAM). LAM can be up to 98 per cent effective.

LAM will only work for you, though, if:

• your baby is younger than six months old
• your period hasn’t returned
• you're exclusively breastfeeding your baby on demand, both night and day

There are some circumstances where you shouldn't use LAM as contraception. For example, if you're taking certain medications. This is because they may make your baby slightly drowsy and therefore less likely to feed as often.

Speak to your child health nurse or a breastfeeding specialist before you start using LAM. She can talk you through any potential problems, and give you advice on how to use the method effectively.

Exclusive breastfeeding on demand usually means a minimum of six long breastfeeds every 24 hours. If you want LAM to work, don't leave a gap between feeds of longer than four hours during the day, or six hours at night. And don't give other fluids or solid food to your baby at all.

With LAM, your breasts need to supply all your baby's suckling needs, so avoid using a dummy or a bottle. Your baby's suckling stimulates the hormones that suppress ovulation.

Once your baby stops exclusively breastfeeding and suckling at the breast for comfort, breastfeeding becomes less effective as a method of contraception. So if you start combining breastfeeding with formula feeds or solid food, even if your period still hasn't returned, you could be fertile.

Some women have lower levels of the hormone progesterone than others in the months after giving birth. If this is the case, you’re more likely to become fertile earlier. The average for the return of periods in breastfeeding women is about 28 weeks after having a baby.

But periods can return anywhere between 15 and 48 weeks after you've had your baby, if you’re breastfeeding. So it's possible to be menstruating again about three-and-a-half months after you've had your baby, or as late as 11 months or longer.

You may want to use another form of contraception, to be on the safe side.

Once you've stopped breastfeeding and your period has settled back into a pattern, you could try natural family planning (NFP). NFP means avoiding unprotected sex on the fertile days of your menstrual cycle.

It's best to have some training in NFP before you start using it, though, as it may be more difficult to recognise the stages of your menstrual cycle after having a baby and while you’re breastfeeding. You may need to find a teacher who specialises in NFP. Visit the Australian Council of Natural Family PlanningOpens a new window for more information.

Find out more about your contraceptive choices.

Reviewed for BabyCenter Australia by Rowena Gray, midwife and lactation consultant