I would say what they imagine their Bible says. If they were really reading what that book says, they'd find no such support for their forced birth dogma – quite the reverse. In fact, the only direct commentary on abortion in the Holy Bible is a passage in the Old Testament, in Numbers chapter five, where the temple priest is commanded to FORCE an abortion (and, some interpretations – including my own – cause sterilization) on woman if she is only even suspected of adultery.

Rabbinic ancient and modern traditions are pro-abortion rights in defense of the mother.