Trisomy 18 in Kuwait

Background Trisomy 18 (Edwards' syndrome, T18) is the second most common tr isomy in man. We describe 118 children with regular T18 who were ascertaine d clinically and cytogenetically in the Kuwait Medical Genetics Centre duri ng 1980-1997. Methods Ascertainment of T18 cases was performed shortly after birth. Chrom osomal studies were carried out in addition to other relevant investigation s. To investigate the factors associated with T18, a case-control study was carried out with 131 normal healthy newborns. Studied factors included mat ernal and paternal age, birth order, abortion, associated malformation, and survival. Multiple logistic regression analysis was used to adjust for con founding between variables. Results There was a preponderance of females among T18 cases (female:male r atio 2.1:1). The majority of T18 cases (53%) died before the second week of life. The most common associated anomalies were: congenital heart (38.1%) and gastrointestinal (25.4%). Multiplicity of malformations was also observ ed. Significant seasonal variation in T18 cases was detected with a peak in spring. Of the 118 T18 cases, 59 were delivered during 1994-1997 (average overall T18 birth prevalence rate 8.95 per 10 000 live births [95% CI: 6.66 -11.23]). Concerning maternal age, 30.5% of the T18 cases' mothers were gre ater than or equal to 35 years compared to 10.7% in the control group. The difference was statistically significant, P = 0.002. Logistic regression an alysis showed that maternal age >30 years was a significant risk factor for T18, after adjusting for confounding with paternal age. Paternal age and a bortion were not found to be significant risk factors. Conclusion Trisomy 18 birth prevalence rate is high in Kuwait with advanced maternal age as a significant risk factor.