Sacral parasite conjoined twin

BACKGROUND. A variant of conjoined twins is one in which one twin is incomp lete. CASE: A female infant was born vaginally at 40 weeks' gestation to a health y primipara. No important abnormalities were noted during prenatal examinat ions. The infant was fully developed in all external aspects except for a p arasitic body conjoined with her sacrococcygeal region. Separated by operat ion 2 weeks after birth, the parasite contained lower limbs, adipose tissue , muscles, and a bowel sac. Over 4 years of observation, no abnormalities h ave been found since the operation. CONCLUSION: Obstetricians should be aware of the existence of a parasite tw in during prenatal examinations and of the importance of the differential d iagnosis of parasite and teratoma, a neoplasm with malignant potential. (Ob stet Gynecol 2001;98:938-40. (C) 2001 by the American College of Obstetrici ans and Gynecologists.).