If you are breastfeeding exclusively, donít expect to start menstruating again until the baby starts to wean.
The timing of the return of the menstrual cycle may be genetically determined, so ask you sisters, mother, aunts when their cycles returned.
If your menstrual cycle does start and you are exclusively breastfeeding, your milk production may go down. The biggest dip is noticed a few days before the bleeding starts and the milk production should increase again after a few days of bleeding. So, if early return of the menstrual cycle is common in your family, consider storing milk ahead of time in order to use it when the production falls below what the baby requires.
Whenever a womenís menstrual cycle restarts and she is exclusively breastfeeding, I make sure that there are no reasons which may have caused the cycle to restart. For instance, sometimes, a baby can be a lackadaisical feeder. In the first few weeks, this baby can get all the milk he/she needs because the mother has abundant production and the milk comes out easily. As the weeks go by, the hormones of milk making calm down, the baby sleeps longer at night, and the supply naturally starts to go down a little bit. Now if this baby does not make a bigger effort to extract the milk, the supply will go down further. If the supply dips too far down, menstruation will restart. In this case, I help the mother take steps to increase the milk production and to improve the babyís feeding habits. Sometimes the menstrual cycle will cease again. If not, the production will continue to vary during different times of the cycle.
If the menstrual cycle restarts earlier than you expected, speak with your doctor as he/she may want to see you and possibly run some blood tests, including checking your thyroid.