How long does marijuana stay in a fetus's system?

Im not entirely sure, but i do know how long it stays in your system for generally. Heres a peice from a medical text - ' "How long does marijuana stay in your system?" you need to take into account the fact that there is no simple answer to this question. THC (Tetrahydrocannabinol) can stay in a person's body for as long as 3 to 90 days after smoking or being ingested orally'. So based on this im saying the same thing for breast milk, 90 days is abit long, that would only be if your ill and have a very slow matabolism. I would say based on my experience about 3-20 days for a healthy women.

But remember marijuana 'Will' effect the baby if your pregnant. So it wouldn't be advicable to smoke or drink any toxins while with child.