I am 35 y, preparing to get pregnant soon. i've been smoking for many years, one pack/day. how long should i wait to conceive after i quit smoking.

No cut off date: Active smoking DURING pregnancy has a slight increase in birth defects (the risk of having certain defects is increased less than 10% in a report of 11 million mothers). How fast this risk decreases BEFORE conception has not been published to my knowledge. My guess is that any FORMER smoker (even for only a day) will be OK. Just quit and good luck. Thank your baby for making you healthier.