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Symptoms

By Mayo Clinic staff

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Illustration showing conjoined twins Conjoined twins

There aren't any specific signs and symptoms that indicate a woman is carrying conjoined twins. As with other twin pregnancies, the uterus may grow more rapidly than expected, and mothers of twins may also have more fatigue, nausea and vomiting early in the pregnancy.

How twins are joined
Conjoined twins are usually classified according to where they're joined, and there are many ways that conjoined twins may be connected. Some of the more common ways include:

  • Joined at the chest. One of the most common of conjoined twins, thoracopagus twins are joined at the chest. They often have a shared heart and may also share one liver and upper intestine.
  • Joined near the bellybutton. 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. They generally do not, however, share a heart.
  • Joined at the base of the spine. Pygopagus twins are joined at the base of the spine and commonly face away from one another. Some pygopagus twins share the lower gastrointestinal tract, and a few share the genital and urinary organs.
  • Joined at the pelvis. Ischiopagus twins are joined at the pelvis. Many ischiopagus twins share the lower gastrointestinal tract, as well as the liver and genital and urinary tract organs. Each twin may have two legs or in some cases, one pair of legs and even a fused leg, though that's uncommon.
  • Joined at the head. Craniopagus twins are joined at the head. Craniopagus twins share a portion of the skull, and possibly brain tissue. This sharing may involve the cerebral cortex — the part of the brain that plays a central role in memory, language and perception.

In rare cases, twins may be asymmetrically conjoined, with one twin smaller and less fully formed than the other (parasitic twins).

Causes Definition
References
  1. Gabbe SG, et al. Obstetrics: Normal and Problem Pregnancies. 6th ed. Philadelphia, Pa.: Saunders Elsevier; 2012. http://www.mdconsult.com/das/book/body/208746819-4/0/1528/0.html. Accessed Feb. 10, 2013.
  2. Wen XR, et al. Thoraco-omphalopagus conjoined twins: Impact of ultrasound assessment on successful surgical separation. Clinical Imaging. 2013;37:138.
  3. Mandy GT. Neonatal outcome, complications, and management of multiple births. http://www.uptodate.com/home. Accessed Feb. 10, 2013.
  4. Jackson OA, et al. Conjoined twin separation: Lessons learned. Plastic and Reconstructive Surgery. 2012;129:956.
  5. Chen CP, et al. Conjoined twins detected in the first trimester: A review. Taiwanese Journal of Obstetrics & Gynecology. 2011;50:424.
  6. Rhodes JL, et al. Preoperative planning for the separation of omphalopagus conjoined twins The role of a multicomponent medical model. Journal of Craniofacial Surgery. 2013;24:175.
  7. Mutchinik OM, et al. Conjoined twins: A worldwide collaborative epidemiological study of the International Clearinghouse for Birth Defects Surveillance and Research. American Journal of Medical Genetics Part C: Seminars in Medical Genetics. 2011;157:274.
  8. Cunningham FG, et al. Williams Obstetrics. 23rd ed. New York, N.Y.: The McGraw-Hill Companies; 2010. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=46. Accessed Feb. 11, 2013.
  9. Chasen ST, et al. Twin pregnancy: Prenatal issues. http://www.uptodate.com/home. Accessed Feb. 10, 2013.
  10. Sharma D, et al. Cephalothoracopagus janiceps asymmetros twins: Antenatal sonographic diagnosis. Journal of Clinical Ultrasound. 2013;00:1.
  11. Rios LT, et al. Prenatal diagnosis and postnatal findings of cephalothoracopagus janiceps disymmetros: A case report. Case Reports in Medicine. 2012;00:1.
  12. Roque H, et al. Monoamniotic twin pregnancy. http://www.uptodate.com/home. Accessed Feb. 10, 2013.
  13. Harms RW (expert opinion). Mayo Clinic, Rochester, Minn. Feb. 15, 2013.
DS00869 April 10, 2013

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