Yes. In general, you're less fertile, but not infertile, while
breastfeeding. Although you may not menstruate for months after giving
birth, your body usually releases its first postpartum egg before you get your first period. So you won't know you've ovulated until two weeks later — when you menstruate.
If you know you don't want to get pregnant while nursing, begin using birth control as soon as you start having sex again. Many doctors recommend barrier methods such as condoms or a diaphragm, but some think the newer low-dose oral contraceptives
are safe to use while breastfeeding and pose no harm to your baby. Ask
your doctor about the "mini-pill," which doesn't contain estrogen, a
hormone that can interfere with lactation, only progestin.
That
said, if you're breastfeeding your baby exclusively, day and night, you
may not menstruate again for a year or even longer after giving birth.
If your baby sleeps through the night at an early age, your period
probably will return more quickly — typically in three to eight months.
The same is true if you're supplementing with formula.
In other
words, the more often your baby nurses, the longer it may be before you
get your period again. Experts believe this is because breastfeeding
curbs the hormones that trigger ovulation. But remember, you could start
ovulating again at any time after three months of lactation, and you
probably won't know when it happens. If you want to make sure you don't
get pregnant, use some form of birth control every time you have sex.