Surveillance of congenital malformations in Belarus. Chernobyl aftermath

Full text: In order to study possible genetic effects of the Chernobyl accident in human population a comparative analysis of the prevalence at birth of congenital malformations (CM) was performed on region and area administrative levels basing on the data of Belarus registry of CM permanently functioning since 1979. An attempt was made to evaluate dose dependence of the effects under study. We analyzed time trends of the prevalence at birth of 9 so called 'mandatory registered' nosologic units of CM. These group of CM could be easily diagnosed within the neonatal period and were assigned for registration at creation of the registry. Over 12 thousand cases registered within the period of 1981 to 2004 in 4 regions as well as about 3 thousand cases found in 47 rayons highly contrasting by radiation exposure were scrutinized. No long-term impact of the Chernobyl release on prevalence rates of surveyed CM was shown. Since the middle 80-s a similar steady increasing trend was observed as in contaminated, as in control areas with a tendency to stabilization after middle 90-s. We fail to reveal a dose dependence for CM prevalence rates calculated for the whole post-accidental period. Nonetheless, during the first years after the accident situation in contaminated areas was notably different from those in the control. Within the period of 1987 to 1989 a significant access of CM prevalence was registered in the strict radiological control area (Cs 137 soil contamination over 555 kBq/m2) as compared to non-contaminated zone. Relative risk was estimated as RR1987-1989 = 1.57 with 95% confidence interval being 95%CI = [1.29; 1.89]. Before the accident no difference in prevalence rates was marked (RR1981-1986 = 0.93; 95%CI = [0.80; 1.09]); nor it was evident in the farther post-accidental period (RR1990-2004 = 0.99; 95%CI = [0.80; 1.09]). Anomalies with high contribution of dominant de novo mutations (polydactyly, reduction defects of limbs and multiple CM) played principal role in the revealed increase. For this CM group a correlation with the estimated effective dose values was observed within the corresponding time period, no such relationship was marked for other analyzed CM, however. Analysis of the farther period failed to reveal a similar association for any group of CM under study. Thus, adverse effect of the Chernobyl accident on fetal development could not be excluded only within the first years after the accident. Peculiarity of the group of anomalies, chosen for the study, limits the impact of screening effect; however, it could not be completely ruled out because of ecological study design. Obtained results need to be confirmed in consecutive series of case-control and cohort studies. Extensive implementation of prophylactics of CM in the early 90-s made it possible to maintain the CM prevalence rates among newborns at the pre-accidental values. Currently over 30% of mandatory registered CM and about 20% of all CM in Belarus are registered among fetuses aborted for genetic reasons. Nevertheless, rather high level of CM prevalence in the republic insists farther improvement of the prophylactics of malformed children birth. For this purpose similar measures seems to be appropriate as for the residents of contaminated, as non-contaminated areas, since currently no substantial difference in time trends are traceable. The most perspective way of improvement of CM prenatal diagnostics is enlargement of the group of women that undergo ultrasound screening of I and II trimesters in specialized centers of prenatal diagnostics