No, it is not scientifically possible for a woman to become pregnant a second time while already being pregnant. Pregnancy occurs when a fertilized egg implants itself in the uterus, and the development of a fetus begins. During pregnancy, hormonal changes prevent the release of additional eggs from the ovaries and the occurrence of ovulation. As a result, the woman does not have menstrual cycles or release new eggs during pregnancy.
While it is technically possible for a woman to release multiple eggs during ovulation and conceive fraternal twins or multiples, this occurs prior to the first pregnancy. It is not possible for a woman to conceive another pregnancy after she is already pregnant. Each pregnancy is a distinct and separate event.