Table I.

Features of conditions of numeric chromosome abnormalities which are associated with HPE^a.

	Trisomy 13	Trisomy 18	Triploidy
Prevalence among recognized conceptionsb,c	1/5,000	1/2,000	1/22,000
Livebirth prevalence b,c	1/11,000	1/7,000	<1/450,000
HPE incidence	Up to 39%d	Rare	Rare
Median survival for liveborn infants	7 days	7 days	<24 hours
Other cardinal features	Deafness, microcephaly, cleft lip/palate, capillary angiomata, polydactyly, cardiac defects, genital defects	Prominent occiput, clenched hand, with 2nd digit overlapping over 3rd and 5th over 4th, cryptorchidism, congenital heart defects	Large placenta, growth restriction, hypertelorism and eye defects, cardiac, genital defects

^aData summarized from Smith’s Recognizable Patterns of Human Malformations and Carey [2005] except where otherwise noted.

^b[Crider et al., 2008; Cragan and Gilboa, 2009].

^dSubtle midline forebrain anomalies appreciable on pathologic examination may occur at an even higher frequency [Moerman et al., 1988].