Pré-Natal

Prenatal Diagnosis and Genetic Counseling for Mosaic Trisomy 13

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Chih-Ping Chen1,2,3,4,5,6*
1Department of Obstetrics and Gynecology and 2Medical Research, Mackay Memorial Hospital, Taipei, 3Department of Biotechnology, Asia University, 4School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung, 5Institute of Clinical and Community Health Nursing and 6Department of Obstetrics and Gynecology, National Yang-Ming University, Taipei, Taiwan.
 
Resumo / Summary
Counseling parents of a fetus with trisomy 13 mosaicism remains difficult because of the phenotypic variability associated with the condition; some patients exhibit the typical phenotype of complete trisomy 13 with neonatal death, while others have few dysmorphic features and prolonged survival. This article provides a comprehensive review of the prenatal diagnosis and genetic counseling for mosaic trisomy 13, including confined placental mosaicism 13, mosaic trisomy 13 diagnosed at amniocentesis, and phylloid hypomelanosis in association with mosaic trisomy 13. [Taiwan J Obstet Gynecol 2010;49(1):13–22]
 
Key Words: confined placental mosaicism, mosaicism, phylloid hypomelanosis, prenatal diagnosis, trisomy 13
 
 

The Risk of Fetal Loss Following a Prenatal Diagnosis of Trisomy 13 or Trisomy 18

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Joan K. Morris1* and George M. Savva2
1Centre for Environmental and Preventive Medicine, Wolfson Institute of Preventive Medicine, St. Bartholomew’s and the London, Queen Mary’s School of Medicine and Dentistry, Charterhouse Square, London, UK
2Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK
Received 12 July 2007; Accepted 23 November 2007
 
The objective of this study is to determine the risk of fetal loss (spontaneous abortion or stillbirth) following a prenatal diagnosis of trisomy 13 (T13; Patau syndrome) or trisomy 18 (T18; Edwards syndrome). Five regional congenital anomaly registers in England and Wales provided details on the outcomes of 198 pregnancies prenatally diagnosed with T13 and 538 prenatally diagnosed with T18. For each pregnancy the time from prenatal diagnosis until birth, miscarriage or termination occurred was calculated and these times were analyzed using Kaplan–Meier survival functions. Our results showed that between 12 weeks gestation and term an estimated 49% (95% CI: 29–73%) of pregnancies diagnosed with T13 and 72% (61–81%) of pregnancies diagnosed with T18 ended in a miscarriage or stillbirth. Between 18 weeks and term the proportions were 42% (18–72%) for T13 and 65% (57–79%) for T18 and between 24 weeks and term the proportions were 35% (5–70%) for T13 and 59% (49–77%) for T18. Male fetuses with T18 appeared to be more likely to be lost than female fetuses. These are the most precise estimates currently available for the risk of loss in a general population. These estimates should be useful in counseling women who are carrying an affected fetus and knowing the risk of fetal loss is essential to compare the performance of prenatal screening programs occurring in the first and second trimester. 2008 Wiley-Liss, Inc.
 
Key words: trisomy 13; trisomy 18; spontaneous fetal loss
 

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

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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.

[…]

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.