If a woman has 3 glasses of wine how long can she breastfeed?

Hard to say. You drop your blood alcohol content by half every 3-4 hours but the milk you make will retain some. There in so known safe exposure level for alcohol in infancy, when nerves are growing fast in their brain. Alcohol breakdown products are toxic to brain cells even in small amounts,so its hard to be sure when your milk would be free of it.There is controversy over the safety of drinking while BF.
Concerned. Great that you are breastfeeding and concerned about your kid's safety to ask this question. Better safe than sorry. If this is not just a one time thing, and you drink somewhat regularly, please be aware of the data showing maternal alcohol consumption reduces milk secretion, increases risk of sids and reduces total duration of breastfeeding. Hope this helps. Good luck to you and your family!
Wine/breastfeed. I suspect you are asking how long she should refrain form breastfeeding if she had some alcohol. 3 glasses of wine, lets say over a 2-4 hour period, would raise the blood alcohol slightly. The amount then transferred over to breast milk is low of that amount. I would not interrupt the breast feeds at all for that low amount of consumption, but you could pump and dump 1 feeding if concerned.