Numbers 5:27
NKJV - 27 When he has made her drink the water, then it shall be, if she has defiled herself and behaved unfaithfully toward her husband, that the water that brings a curse will enter her and become bitter, and her belly will swell, her thigh will rot, and the woman will become a curse among her people.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Based on the NIV Bible translation this means the baby miscarries or aborted. Which is very controversial in today's politics.
NIV translation:
22 May this water that brings a curse enter your body so that your abdomen swells or your womb miscarries.”
My opinion is that scripture doesn't say anything about the woman being pregnant. It mainly talks about the husband being jealous and not trusting his wife.
By drinking the bitter water it will show if she is lying. Belly will swell as in having excess gas to cause diarrhea (curse goes into the bowels) and the thigh rot relates to STD, herpes or leprosy. Something that makes her unclean.