Genetic monitoring of the human population from high-level natural radiation areas of Kerala on the southwest coast of India. I. Prevalence of congenital malformations in newborns

In the densely populated monazite-bearing sands of Kerala, on the southwest coast of India, natural radiation dose rates range from 1.0 to over 35.0 m Gy per year in certain well-defined high-level natural radiation areas. As a part of the program to assess the health effects of this naturally occurr ing high-level natural radiation on human populations, monitoring of newbor ns is being undertaken to determine the incidence of congenital malformatio ns. From August 1995 to December 1998, a total of 36,805 newborns were scre ened, including 212 (0.58%) stillbirths. There were 36,263 singletons, 536 (1.45%) twins, and 6 born as triplets. The overall incidence of malformatio ns was 1.46% and was dependent on maternal age. The stillborns exhibited a very high malformation rate of 20.75% compared to 1.35% among the live birt hs. Likewise, twins also had a higher malformation rate (2.99%) compared to singletons (1.44%). About 3.5% of the newborns originated from consanguine ous marriages. Consanguinity also led to a relatively higher rate of malfor mations (1.97%) as well as of stillbirths (1.18%). About 92% of the deliver ies took place by the maternal age of 29 years and only 1.2% among women ab ove 34 years old. The stratification of newborns with malformations, stillb irths or twinning showed no correlation with the natural radiation levels i n the different areas. Thus no significant differences were observed in any of the reproductive parameters between the two population groups based on the monitoring of 26,151 newborns from high-level natural radiation and 10, 654 from normal-level natural radiation (dose rate less than or equal to 1. 5 mGy/year) areas of the Kerala coast. (C) 1999 by Radiation Research Socie ty.