There's an important piece of information that most Americans just don't know, and that's that breastfeeding as commonly practiced today in the U.S. is nothing like breastfeeding practiced back in less modern times. If you're breastfeeding on a schedule, using bottles and pacifiers and putting the baby to bed in a crib, you're going to get your period back fairly soon. You can absolutely conceive.

However, the type of breastfeeding that was normally practiced by our ancestors was very different. We nursed our babies MUCH more frequently. We started solids later. We slept with our babies and they nursed all night. We didn't have plastic pacifiers. Under those conditions -- what they call ecological breastfeeding, fertility is held at bay for quite a while. Until modern times, very few women could conceive right away after giving birth, unless the baby died/she used a wet nurse/she tried feeding the baby something else. Laurel Thatcher Ulrich talks about this in her book about a colonial midwife -- the moms did not conceive every year.

My own experience bears this out. After my first baby, I returned to work part-time, and my period returned at 6 weeks or so. But after my second baby, I stayed home. We had a family bed, and my second baby nursed all night. My period didn't come back for around 18 months -- that's despite the fact that my children never had any formula at all. Still, the timing of milk removal was very different between the two. So yes, women today CAN expect to get pregnant, and very, very often do. If a woman wants not to get pregnant while breastfeeding, she needs to use contraception -- or, if she doesn't believe in it, she has to breastfeed the way women did in history -- quite frequently, with no pacifier, early solids, bottles, or separations from the baby.