IVF twin transfer 42 days waist acid may be normal, or it may be a manifestation of preterm miscarriage, then it is not normal. In vitro fertilization also refers to embryo transfer, usually, in vitro fertilization of twin 42 days of waist acid is mostly considered to be the manifestation of early pregnancy reaction, belongs to the normal physiological phenomenon, do not need to worry too much, mainly because of the estrogen in the body of the woman is elevated, and the uterus, ovaries will innervate the reproductive strand nerve, coupled with the physiological activities of the pregnancy, so it will cause waist acidity. If the backache is strong, accompanied by abdominal pain and vaginal bleeding, it is a manifestation of preeclampsia, which is abnormal, and twin fetuses are more likely to have preeclampsia. To summarize, it is recommended that women with back pain on the 42nd day of IVF transplantation for twin fetuses should go to the hospital in time to clarify the specific cause and cooperate with the doctor for active treatment if necessary.