I was conceived when my mom was exclusively breastfeeding my 5-month old sister. The pregnancy came as a complete surprise since my mom had not yet had a period. I do know that most of us siblings slept through the night fairly early on, as evidenced by my mom's frequent asking "So is Zari sleeping through the night yet?" starting when she was about four months old. I suspect that the cessation of frequent night nursing explains why I was conceived when, stastically, I shouldn't have been!
Some information about Lactational Amenorrhea from Kellymom, much of which came from Jen O'Quinn's Natural Child Spacing and Breastfeeding:
The Exclusive Breastfeeding method of birth control is also called the Lactational Amenorrhea Method of birth control, or LAM. Lactational amenorrhea refers to the natural postpartum infertility that occurs when a woman is not menstruating due to breastfeeding...
Exclusive breastfeeding (by itself) is 98-99.5% effective in preventing pregnancy as long as all of the following conditions are met:
You can achieve higher effectiveness by practicing ecological breastfeeding:
- Your baby is less than six months old
- Your menstrual periods have not yet returned
- Baby is breastfeeding on cue (both day & night), and gets nothing but breastmilk or only token amounts of other foods...
If you practice ecological breastfeeding:
- keeping baby close
- breastfeeding on cue (day and night)
- using breastfeeding to comfort your baby
- breastfeeding in a lying-down position for naps and at night
- using no bottles or pacifiers
- Chance of pregnancy is practically zero during the first three months, less than 2% between 3 and 6 months, and about 6% after 6 months (assuming mom's menstrual periods have not yet returned).
- The average time for the return of menstrual periods is 14.6 months.
- Moms whose cycles return early tend to be infertile for the first few cycles. Moms whose cycles return later are more likely to ovulate before their first period.