Pyridoxine-dependent seizure (PDS) is a rare, autosomal recessive disorder characterized by drug-resistant neonatal seizures. About 20% of mothers experience abnormal foetal movements during pregnancy, and birth is complicated in a third of children. It is thought that early postnatal treatment improves cognitive development. However, the benefit of antenatal treatment is still under debate. Some case reports support favourable outcome of antenatal treatment (n = 3 patients) while other case reports show no or little advantage in outcome (n = 5). We present two well documented Dutch families with metabolic and DNA confirmed PDS including long term follow-up. In these families the first born child could be studied as a natural ‘control’ of the second child. The mothers started pyridoxine in the first trimester of their second pregnancy and pyridoxine was well tolerated by the mother and foetus. The mothers did not experience abnormal foetal movements and labour and birth were uncomplicated in both. At follow-up the second child developed better than the older sibling. Conclusion We believe that in families with PDS, antenatal treatment should be advised. Antenatal treatment does not seem to harm the mother and the foetus, it might prevent the occurrence of intra-uterine seizures, and can decrease the risks of complicated birth. Antenatal treatment might also improve the long-term neurological outcome.