I thought you aren't supposed to get your period when you are nursing? 

Yes, women who breastfeed are not supposed to ovulate and therefore aren't supposed to get a period in the months after they deliver.   It sometimes doesn't work that way. 

Lactational Amenorrhea (no period while you are nursing) works if you nurse "intensively" meaning no more than 4 hours between daytime feedings and no more than 6 at night.  Frequent nursing alters pituitary production of a couple of hormones that make you ovulate. We're not quite sure if pumping is as effective as nursing at the breast, so if you are pumping frequently during the daytime, you may still get your period back.  The introduction of formula supplementation or solid foods spaces out the time between breastfeeding and can then cause you to ovulate and then get your period (and that means you are fertile again!)

So then, does the return of your period mean that your supply is bad or that you are going to have to wean?  Nope.  Sometimes there is a temporary drop in your supply and some kids don't like the taste of the milk during that time, but that's it.  Nothing more serious going on.

updated May 8, 2007