Embryo Project Encyclopedia Articles

Fetus in fetu is a rare variety of parasitic twins , where the developmentally abnormal parasitic twin is completely encapsulated within the torso of the otherwise normally developed host twin. In the late eighteenth century, German anatomist Johann Friedrich Meckel was the first to described fetus in fetu, which translates to “fetus within fetus.” Fetus in fetu is thought to result from the unequal division of the totipotent inner cell mass , the mass of cells that is the ancestral precursor to all cells in the body. The unequal division is thought to occur during the formation of the blastocyst, which can also result in parasitic and conjoined twins . Fetus in fetu represents a developmental anomaly that has prompted developmental biologists to further examine the mechanisms for how twins arise.

Jesse Bennett, sometimes spelled Bennet, practiced medicine in the US during the late eighteenth century and performed one of the first successful cesarean operations, later called cesarean sections, in 1794. Following complications during his wife’s childbirth, Bennett made an incision through her lower abdomen and uterus to deliver their infant. Bennett’s biographers report that his operation was the first cesarean section where both the pregnant woman and the infant survived. Previously, physicians used cesarean sections to save the fetus from a pregnant woman who had already died during childbirth. Bennett successfully performed a cesarean section, a procedure used worldwide in the twenty-first century when a vaginal delivery is not possible or would pose a risk to the woman or fetus.