The New England Journal of Medicine recently reported on a large clinical trial describing subjects with meningomyelocele (MMC) that were randomised to surgical repair either in the fetal period or to standard postnatal repair.1 This report has generated enormous excitement, but also vigorous debate. This study – the ‘MOMS’ trial (Management of Meningomyelocele Study) – is the first to demonstrate that fetal intervention might alter the natural history of a congenital neurologic malformation. Meningomyeloceles are the most common form of neural tube defects and result from disturbed neurulation during the third and fourth weeks of gestation.2 Although the incidence varies markedly across different regions, MMC occurs in approximately 300 000 infants worldwide each year.3 The incidence of live births with MMC has decreased significantly in recent decades through combined effects of improved diagnosis and dietary supplementation. Improved prenatal detection by serum markers and fetal imaging has resulted in an escalation in pregnancy termination, particularly in regions with access to prenatal care and where terminations are culturally accepted. For example, in the UK, 72% of prenatally diagnosed cases of MMC were aborted, with similar results reported in the USA, Australia and parts of Western Europe.4 In the early 1990s, the association between maternal folate deficiency and development of MMC was described.5 This resulted in regulation mandating the fortification of cereal grains in the USA, Canada, and elsewhere, as well as campaigns for antenatal folate supplementation with a 20–50% reduction of MMC in these countries.6 Subsequently, the incidence of MMC has remained stationary at approximately two cases per 10 000 live births in the USA each year, highlighting the fact that …