The severity of the cramping, contractions and bowel movements can cause baby to have a
bowel movement while in the womb. Baby can then inhale this
bowel movement causing breathing problems, asfixiation and any number of other issues.
Also if baby is not ready or in an awkward position it can cause problems too.
Not every case is like this, some ppl take it with no problems, but I wouldn't take the risk.
Ask your Dr first before taking it.