Materials and Methods: Retrospective single center matched case control study, analysis of the association between maternal BMI and the frequency and type of fetal anomalies and establishment of the sensitivity of ultrasound scans in relation to the maternal BMI.

Results: There were 182 fetal anomalies which were matched with healthy controls. The main findings of the study are, that maternal BMI was significantly increased in pregnancies with fetal anomalies, in particular in overweighed women the risk was 1.6 fold increased for a fetal anomaly, in obesity it was even 2.1 fold. The most common anomaly were cardiac defects, urogenital defects were second. The chance for a neural tube defects was 10.7 times increased. Although vision was impaired, 94.7% of the cases were diagnosed correctly by prenatal ultrasound, the detection rate deteriorating with decreasing sensitivity in obese women.

Conclusion: There is an increase of fetal anomalies with increasing maternal weight whereas the detection rate for fetal defects declines.