Consuming Marijuana During Pregnancy Does Not Make A Mother Unfit 
Forbes 11.19.16
_At one month, the children of the marijuana users actually had better scores, which the researchers attributed to “the cultural positioning and social and economic characteristics of mothers using marijuana that select for the use of marijuana but also promote neonatal development.”_
From a widely cited 1994 study about Jamaican women. 

It also mentions a woman who used cannabis tea to treat morning sickness & severe sciatic nerve pain thinking it was preferable to painkillers she had been prescribed.

http://www.forbes.com/sites/jacobsullum/2015/11/19/consuming-marijuana-during-pregnancy-does-not-make-a-mother-unfit/#17077c7443b9

(I recall reading the _Canadian Whole Earth Almanac_ decades ago indicating that women in Canada had used marijuana to ease childbirth...probably a lot more comfortable than drugs ..
or Caesarean sections of which it has been estimated that half are unnecessary in the USA).