Spina bifida and anencephaly: are miscarriages a possible cause?

The marriage-to-conception interval in 151 pregnancies producing infants with anencephaly or spina bifida was not significantly different from that in 218 pregnancies resulting in normal infants. Significantly more miscarriages occurred before than after the birth of 285 infants with anencephaly or spina bifida, but in 133 controls no before-after difference was observed. These observations seem to favour the idea that miscarriages are a manifestation rather than a cause of anencephaly and spina bifida.