It doesn't start labor and is safe throughout pregnancy.
But.... It does tone your uterus so a lot of women notice an increase in contractions. Usually they're just BH.
18 oz in the first day sounds like enough to throw your contractions up a notch. I started with just 8oz a day for a few weeks.
Also, loose tea is more potent. So it's like you drank even more.
SAHM to Magnolia May (09/10), Luke Russett (04/13) and expecting 11/16. Wife and best friend to my airman.