[Seasonality of omphalocele in northern Germany]

Omphalocele is a rare congenital abdominal wall defect that has been attributed to environmental factors such as increased levels of herbicides in surface water. We wanted to verify a seasonal variation of the incidence of Omphalocele and thus to identify possible environmental factors in an area in Northern Germany that is characterized by a predominantly agricultural setting.

A retrospective analysis of all pregnancies (n = 28 935) screened by ultrasound at our University Hospital between January 1, 1993 and December 31, 2007 was carried out. After identification of fetuses with persisting Omphalocele, analysis for additional structural defects and for chromosomal anomalies, such as trisomy 18, was carried out. We further categorized all patients with regard to the date of conception during summer (April-September) and winter months (October-March). Categorical variables were compared by the Mann-Whitney-U test and were considered statistically significant when two tailed analyses yielded p = 0.05.

There was no significant difference in the seasonal distribution of conception neither for all fetuses (p = 0.70) nor for fetuses with Omphalocele (p = 0.94). The results were constant for fetuses with isolated Omphalocele and with additional malformation and for those with Omphalocele and associated chromosomal anomalies. The incidence of fetal Omphalocele has remained relatively stable within the last 15 years. No significant difference was found in the seasonal incidence of Omphalocele in patients from an urban or rural background.

Since we were unable to demonstrate a relationship between the time of conception and the incidence of fetal Omphalocele in our cohort of pregnant women from a predominantly agricultural background, other factors should be investigated for possible associations with the onset of Omphalocele.