Natural Outcome of Trisomy 13, Trisomy 18, and Triploidy After Prenatal Diagnosis

Introduction

Trisomy 18 (Edwards syndrome) and trisomy 13 (Patau syndrome) are, along with trisomy 21 (Down syndrome), the most common autosomal aneuploidies in the newborn, with a prevalence at birth of between one in 3,000 and one in 15,000 [Smith, 1964; Carter et al., 1985; Baty et al., 1994; Hasslod and Hunt, 2001].

Triploidy belongs to the polyploid types, and is estimated to occur in 1–2% of recognized human conceptuses. Most pregnancies with triploidy, however, are aborted spontaneously in early gestation so that the prevalence at birth of triploidy is rare: approximately one in 50,000 newborns [Doshi et al., 1983; McFadden and Kalousek, 1991].

All these chromosomal abnormalities belong to disorders which are compatible with life, but which are also associated with a high rate of spontaneous abortion, intrauterine death, and a short life span. [O’Connor, 2008].

Over the last 30 years, prenatal diagnosis of these disorders has improved due to the increasing use of fetal ultrasound screening methods in the first and second trimesters, and invasive diagnostic methods such as amniocenteses. In Austria, as in many other countries, parents are given the opportunity to terminate a pregnancy (artificially induced abortion) if a severe fetal disorder has been diagnosed. Only a few parents, therefore, decide to continue with a pregnancy after a prenatal diagnosis of trisomy 13, trisomy 18, or triploidy.

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The aim of this study was to analyze the outcome of continued pregnancies after prenatal chromosomal diagnosis of trisomy 13, trisomy 18, or triploidy. These new data are aimed at improving the consulting process for parents who are confronted with prenatal diagnoses of these chromosomal abnormalities.