disorders and birth defects occur more frequently in identical fetuses than in
fraternal ones. In rare cases, problems occur when the genetic material
(chromosomes) in the fertilized egg does not split evenly. This can result in
severe mental or physical defects in one or more fetuses.
Conjoined (Siamese) twins occur rarely. This occurs when the egg does not
split completely and the fetuses are partially joined.
Most doctors advise pregnant women to be screened for genetic disorders.
Primary Medical Reviewer
Sarah Marshall, MD - Family Medicine
Specialist Medical Reviewer
William Gilbert, MD - Maternal and Fetal Medicine
July 8, 2011
WebMD Medical Reference from Healthwise
July 08, 2011
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