Small biparietal diameter and head circumference are part of the phenotype instead of independent prognostic markers in fetuses with spinal dysraphism.

OBJECTIVE: The aim of this retrospective study was to assess the fetal biparietal diameter (BPD) and head circumference (HC) in the second trimester of pregnancy in fetuses with open spinal dysraphism. METHODS: BPD and HC were measured at 16-26 weeks in 74 fetuses with open spinal dysraphism and compared with reference values. RESULTS: BPD was smaller in fetuses with open spinal dysraphism. Of all cases with open spinal dysraphism, 62.2% had a BPD <3rd percentile and 79.7% had a BPD <10th percentile. Of all patients, 54.1% had an HC <3rd percentile and 74.3% had an HC <10th percentile. CONCLUSION: Almost all fetuses with open neural tube defects have a smaller BPD and HC at 16-26 weeks compared with reference values, which implicates that this is part of the phenotype of children with open spinal dysraphism instead of an independent prognostic marker for a poor cognitive outcome.