I've been using breastfeeding as a contraceptive, and I didn't even know it!
Blast. 98%? I only had a 2% chance of getting pregnant back in March and April and I wasted so much money (and hope) on pregnancy tests! Haha. :)
I am supplementing earlier next time...for so many reasons!
From Wikipedia and the World Health Organization:
Use of breastfeeding as contraceptive
The World Health Organization states that demand breastfeeding is more than 98% effective as a contraceptive in the first six months postpartum. This effect is said to be responsible for the natural spacing of children seen in countries where contraception is not widely available, and is thought to be an evolutionary means of ensuring adequate care is provided to each newborn. The 98% effectiveness applies only if three criteria are met:
1. The mother has had no menstrual periods at all (amenorrhea)
2. The baby is exclusively breast-fed
3. It is six months or less since birth.
* A fourth criterion has also been mentioned: The baby does not go for longer than 5 hours between feedings (i.e. while sleeping)
If one or more of these conditions are broken, lactational amenorrhea is no longer a reliable form of birth control. This contraceptive method is highly effective as long as the three conditions stated above are fulfilled. Further, the WHO suggests that a woman who is still amenorrheic (no menstrual periods) has a less-than-5% chance of getting pregnant in the first year of her baby's life, as long as she is still breastfeeding on demand.