Two words: Nipple Stimulation. It worked for me! It tricks your body into thinking you’re breastfeeding causing your uterus to contract (which naturally occurs after birth). We did it one night and I woke up the next morning in labour.
I am almost 40 weeks along, and have drove myself nuts trying to have this baby and I have tried the castor oil, sex, walking, spicy food, the nipple thing (but then I found out you have to do 3 one hour’s sessions to get it started and it needs to be monitored in the hospital or something).