The incidence of neural tube defects in Norway and the Arkhangelskaja Oblast in Russia and the association with maternal age.

OBJECTIVE

To determine the incidence of isolated anencephaly and spina bifida in the Arkhangelskaja Oblast (AO) in Russia and in Norway, and to study the maternal age distribution of these congenital defects.

DESIGN

A register-based incidence study.

SETTING

Two different populations in Northern Europe.

POPULATION

All registered fetuses and newborns with at least 12 weeks' gestation in the populations of AO (1995-2004) and Norway (1999-2003) were included. A total of 141,159 in AO and 293,708 in Norway.

METHODS

Data were obtained from the malformation register in AO and the Medical Birth Registry of Norway. Main outcome measures. Total and maternal age-group specific incidence of anencephaly and spina bifida.

RESULTS

A total of 298 newborns and abortuses had one of the defects in AO (21.1/10,000 (95% confidence interval:+/-3.4)) and 317 (10.8/10,000 (+/-1.2)) in Norway. The incidence of anencephaly was 10.7/10,000 in AO and 5.5 in Norway, and of spina bifida 10.4 and 5.3, respectively. An inverse association between the age of the pregnant women and the incidence of neural tube defects was observed in both populations; for both anencephaly and spina bifida in AO; but only for anencephaly (age < 30 years) in Norway.

CONCLUSIONS

The incidence of both anencephaly and spina bifida was higher in a northern population of Russia than in Norway. The burden of anencephaly was highest in the youngest maternal age group in both populations. The relatively high incidence of both anencephaly and spina bifida in the Russian population warrants further studies.