Lethal Developmental Defects: An Overview

About 3% of all conceptions are associated with major congenital malformations, many of them are lethal developmental defect and genetic in origin or teratogenic (adverse effects of the environment during gametogenesis or early embryogenesis). Genetics with or without adverse environment has role in virtually every developmental defect/malformation disorders in causation, predisposition, susceptibility & modulation of disease. Advances in genetics, introduction of triple marker screening, routine obstetric ultrasound examination into obstetric practice & accesses to prenatal diagnosis helped in secondary prevention (early detection & termination) of lethal developmental defects. Ultrasound detection of fetal developmental defects/malformation is common now and often decision on pregnancy solely based on ultrasonic morphological description. This practice leads to difficulty in providing accurate counseling as well as preventing disorder in subsequent pregnancy, in particular early. Hence an understanding of reproductive genetics of major developmental disorders is important for today’s perinatal care specialists. This overview will outline the various lethal developmental defects observed in an advanced reproductive genetics set up and various approaches adopted to derive diagnosis. Detailed assessment of fetus after termination of pregnancy (spontaneous/induced) for fetal anomalies was carried out in most cases. As most cases was referred after termination in formalin routine chromosomal analysis was not possible however, in selected cases targeted FISH analysis with specific chromosomal probe was carried out to confirm clinical diagnosis. Detailed evaluation of fetus is important as this practice often helped in modification of genetic counseling, as well as course of management in the next pregnancy. No molecular diagnostic or screening work was carried out due to non availability of information and facility in past. However, this is important today as many of the lethal developmental defects are yet to be categorized etiopathologically, and hence immediate need is to start clinical registry along with biorepository of developmental defects cases for future research work on informative families, in particular with multiple affected fetuses/sibs, using genomics, proteomics, metabolomics, platforms.