[Prevalence of congenital abnormalities identified in fetuses with 13, 18 and 21 chromosomal trisomy].

Purpose: To describe the prevalence of malformations found in fetuses with trisomy of chromosomes 13, 18 and 21 by identifying the most frequent within each condition.
Methods: A retrospective cross-sectional study with the analysis of trisomy cases of chromosomes 13, 18 and 21 diagnosed through fetal karyotype obtained by amniocentesis/cordocentesis, between October 1994 and May 2014, at a Teaching Hospital in Brazil Southern Region. Malformations identified through morphological ultrasonography were described and, subsequently, confirmed in newborn examinations and/or fetal autopsy. The results were analyzed using Fisher's test and analysis of variance (ANOVA), with a 5% level of significance (p=0.05).
Results: Sixty-nine cases of trisomy were diagnosed among 840 exams; nine were excluded due to outcome outside Hospital de Clínicas de Porto Alegre or incomplete records, remaining 60 cases (nine cases of chromosome 13 trisomy, 26 of chromosome 18, and 25 of chromosome 21). In all three groups, heart disease occurred in most cases; the ventricular septal defect was more prevalent and occurred in 66.7% of the trisomy 13 group. Gastrointestinal abnormalities were more prevalent in the trisomy 18 group, especially omphalocele (38.5%; p<0.01). Genitourinary anomalies were more significantly frequent in the trisomy 13 group (pyelectasis, 55.6% - p<0.01; ambiguous genitalia, 33.3% - p=0.01). Central nervous system defects were identified in all cases of trisomy 13. Facial cracks were significantly more prevalent among fetuses with trisomy 13 (66.7%; p<0.01). Hand and feet malformations significantly differed among the trisomy groups. Hand defects occurred in 50% of trisomy 18 cases, and in 44.4% of all trisomy 13 cases (p<0.01); congenital clubfoot was more common in the trisomy 18 group, being detected in 46.2% of fetuses (p<0.01). The abnormalities were found in 50.9, 27.3 and 21.7% of trisomy 18, 13 and 21 cases respectively.
Conclusion: Many fetal malformations identified at ultrasound are suggestive of trisomy and represent an important tool for etiologic diagnosis and prenatal and pre-conception genetic counseling.