At your first postpartum checkup, you may be surprised when your doctor asks you about birth control. It may come as a shock, but you can get pregnant while breast-feeding.

Women are generally less fertile while breast-feeding, but they aren’t infertile. That means pregnancy is a possibility.

Here’s what you should know about pregnancy while breast-feeding.

The same hormones that allow your body to produce breast milk help it suppress the release of reproductive hormones. Using breast-feeding as a birth control method is sometimes known as the lactational amenorrhea method (LAM).

There are three rules to make LAM effective as a method of birth control:

  • The mother must be exclusively breast-feeding with no supplemental feedings. Nursing should happen at least every three hours during the day and every six hours at night.
  • The baby must be younger than 6 months old.
  • The mother’s menstrual cycle hasn’t yet returned.

If these conditions are all being met, it’s possible for women to remain infertile for more than six months.

Less than 1 in 100 women practicing continuous breast-feeding with no supplemental feedings will become pregnant.

About 2 in 100 women will become pregnant in the first six months if they aren’t practicing continuous breast-feeding. That means they may be supplementing breast milk with formula, they’re going too long between feedings, or their babies are using pacifiers.

If you want to delay ovulation with breast-feeding, follow these tips:

  • Nurse your baby on demand. Don’t worry about schedules. Typically, nursing your baby six to eight times a day is enough to prevent ovulation.
  • Avoid sleep training your baby. Nursing at night is important to suppress fertility.
  • Don’t introduce bottles or pacifiers.
  • Don’t introduce solid foods before your baby is 6 months old.
  • Continue breast-feeding after you do introduce solids.
  • Offer solids as a supplement to breast-feeding for extra nutrition (not as a substitute to nursing).

Frequency is the most critical element to using breast-feeding to delay fertility. Prolactin is the hormone that suppresses ovulation. Nursing your baby often will keep it high. As prolactin levels fall, reproductive hormones rise. And that leads to a return in fertility.

Frequency of breast-feeding will play a role in suppressing reproductive hormones. But individual body chemistry will also have an impact.

Some women who nurse their babies exclusively still find that their periods return quickly. This might even happen within the first few months after birth.

Other moms may supplement with formula and still go a year or longer without menstruating. That’s what makes breast-feeding a risky form of birth control. The variable is individual body chemistry.

When your period does return, no egg is usually released with the first cycle. This is also known as anovulation. In this case, there’s no possibility of pregnancy. But a small percentage of women do ovulate before their first periods. The odds increase the longer it’s been since you last menstruated.

It’s important to think about effective birth control beyond breast-feeding. This is especially true if you aren’t exclusively breast-feeding, your period has already returned, or your baby is older than 6 months.

If you’re breast-feeding and aren’t ready for another pregnancy, a nonhormonal barrier method of birth control is the safest choice. This will help you avoid a decrease in your milk supply.

Options include:

  • condoms
  • diaphragms
  • spermicides
  • IUDs

Another nonhormonal method of birth control that won’t impact breast-feeding is fertility awareness. With these methods, you’ll learn the signs and symptoms of fertility.

Some fertility awareness methods involve charting temperatures. Another requires monitoring your cervical mucus or charting your menstrual cycle so you can avoid unprotected sex on fertile days. But these methods have up to a 24 percent failure rate. They work best for women with regular menstrual periods.

If you and your partner have decided that you’re done having children, a permanent method of birth control like tubal ligation will have no effect on breast-feeding.

If your goal is to become pregnant while you continue to breast-feed your baby, your chances increase the older your baby becomes.

You can encourage the return of your fertility with the following:

  • Make a sudden change to your nursing routine, which will have a bigger impact than a gradual change.
  • Consider weaning your baby during a consistent period every day or at night.
  • Offer solids in place of a nursing session.

Whether you’re trying to have another baby while breast-feeding or trying to prevent pregnancy, it’s important to understand that the possibility of pregnancy exists. With this knowledge, you can take the right steps for you and your family.