I was taking it when I got pregnant with my first and was told to stop taking it. That was 10 years ago so I don't remember specifics, but something along the lines of it causes your cervix to thin. She said it would be fine to start taking later in my pregnancy. Definitely check with your doctor to be sure though! Like I said it was 10 years and things like that sometimes change.
My midwives had me take it late in 3rd tri, and as a vaginal suppository to help thin cervix. For that reason I'd guess it's best not to take until later on but check with your doctor about any supplements for sure!
Re: evening primrose oil
Definitely check with your doctor to be sure though! Like I said it was 10 years and things like that sometimes change.