What is the ruling regarding a man's statement to his wife, "If menstruation does not come, you are divorced," if his wife becomes pregnant after this statement?

What you uttered is the conditional divorce of your wife upon the non-arrival of her menstrual period. If this is what occurred, then the divorce has taken place. If this was not the third divorce, you may take her back as long as she is still in her waiting period (iddah). If the waiting period has ended, you may not take her back except with a new marriage contract. The waiting period of a pregnant woman ends with childbirth. Divorcing a pregnant woman is considered a divorce according to the Sunnah.