Any pregnancy that goes overdue is very prone to meconium. Castor oil, from MY research, doesn't cross the placenta. Do your own research and form your own opinion, but use credible sources, which does NOT include a forum, including MY opinion. You don't know who we are... lol.
Here's what my sister says about her experience: I used castor oil to induce labor - I had a pitocin induction scheduled for 2 days later, due to my baby's size, and wanted to avoid it. I discussed it with my doctor who said it's harmless in her opinion and is worth a shot if I'm willing to deal with the side effects - possible vomiting and definite diarrhea.
I used about half a bottle of castor oil in a large chocolate milk shake at lunch time - 12-1pm. Couldn't taste it. The milk shake was great! I went through my day as usual, no tummy trouble, and didn't think it worked. At around 9 pm, my water broke. THEN, I got the diarrhea. It was awful. I pooped all over the table during delivery, had to poop in a bed pan a few times BEFORE getting to that point because they didn't want me to "poop" the baby out. I was pooping so much that my poor midwife was trying to "plug" my anus so she could see what was going on as baby crowned and everything. My LO WAS born a day after my water broke, though! The castor oil definitely worked! And I was all cleaned out with delivery.
...............Not sure I'd wanna try it. LOL