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Symptoms
By Mayo Clinic staff
The first sign of conjoined twins is the same as for any twin pregnancy: a rapidly growing uterus that's larger than for a single embryo. Mothers of twins may also have severe fatigue, nausea and vomiting early in the pregnancy.
How twins are joined
Conjoined twins are usually classified according to point(s) where they're joined. More than three dozen conjunctions have been identified. Some of the more common include:
- Thoracopagus. One of the most common of conjoined twins, thoracopagus twins are joined at the chest. They always have a shared heart and may also share one liver and upper intestine.
- Omphalopagus. Also common, omphalopagus twins are joined near the bellybutton. Many omphalopagus twins share the liver, and some share the lower part of the small intestine (ileum) and colon.
- Pygopagus. Pygopagus twins are joined at the base of the spine. Some pygopagus twins share the lower gastrointestinal tract, and a few share the genital and urinary organs.
- Ischiopagus. Ischiopagus twins are joined at the pelvis. Many ischiopagus twins share the lower gastrointestinal tract, as well as the genital and urinary tract organs.
- Craniopagus. Craniopagus twins are joined at the head. Craniopagus twins share the skull. Some also share the cerebral cortex — the part of the brain that plays a central role in memory, language and perception.
- Parapagus. Parapagus twins are joined extensively from side to side.
Many conjoined twins have separate arms and legs, but in some cases, limbs are shared. In rare cases, twins may be asymmetrically conjoined, with one twin smaller and less fully formed than the other (parasitic twins).
- From 'monsters' to modern medical miracles: Selected moments in the history of conjoined twins from medieval to modern times. United States National Library of Medicine. http://www.nlm.nih.gov/hmd/conjoined/embryology.html. Accessed Sept. 2, 2008.
- Roque H, et al. Monoamniotic twin pregnancy. http://www.uptodate.com/home/index.html. Accessed Sept. 2, 2008.
- Stone JL, et al. The craniopagus malformation: Classification and implications for surgical separation. Brain. 2006;129(5):1084-1095.
- Spitz L, et al. Success rate for surgery of conjoined twins. The Lancet. 2000;356:1765.
- Wilcox DT, et al. Urological problems in conjoined twins. British Journal of Urology. 1998;81:905-910.
- Carnevale FC, et al. Importance of angiographic study in preoperative planning of conjoined twins: Case report. Clinics. 2006;61(2): 167-170.
- Pajkrt E, et al. First-trimester diagnosis of conjoined twins. Prenatal Diagnosis. 2005;25(9):820-826.
- Kaufman M. The embryology of conjoined twins. Child's Nervous System. International Society for Pediatric Neurosurgery. 2004;20(8-9):508-525.
- Gilbert S. Types of conjoined twins. In: Gilbert S. Developmental Biology. 8th ed.
- Sunderland, Mass.: Sinauer Associates, Inc; 2006. http://8e.devbio.com/article.php?id=112&search=conjoined%20twins. Accessed Sept. 2, 2008.
