Modelling the potential impact of population-wide periconceptional folate/multivitamin supplementation on multiple births

Objective To develop a model of the impact of population-wide periconceptio nal folate supplementation on neural tube defects and twin births. Design A hypothetical cohort of 100,000 pregnancies greater than or equal t o 20 weeks, plus terminations of pregnancy after prenatal diagnosis before 20 weeks. Methods Application of pooled data on the relative risks for neural tube de fects and twins following periconceptional folate from meta-analysis of the randomised trials. Main outcome measures 1. Pregnancies with a neural tube defect (i.e. termin ations of pregnancy, perinatal deaths, and surviving infants); 2. twin birt hs (i.e. preterm births, perinatal deaths, postneonatal deaths, birth defec ts, cerebral palsy); 3. numbers needed to treat. Results The change in neural tube defects would be 75 fewer terminations (9 5% CI -47, -90), 30 fewer perinatal deaths (95% CI 18, -35), and 13 fewer s urviving infants with a neural tube defect (95% CI -8, -16). The change in twinning would be an additional 572 twin confinements (95% CI -100, +1587), among whom there would be 63 very preterm twin confinements (95% CI -11, 174), 54 perinatal and postneonatal deaths (95% CI -9, +149), 48 surviving twins with a birth defect (95% CI -8, +133), and nine with cerebral palsy ( 95% CI -2, +26). The numbers needed to treat for the prevention of one preg nancy with a neural tube defect is 847, for the birth of one additional set of twins is 175, for the birth of one additional set of very preterm twins is 1587, and for the birth of an additional twin with any of the following outcomes (perinatal death, postneonatal death, survival with a birth defec t, or survival with cerebral palsy) is 901. Conclusions Monitoring rates of neural tube defects and twinning is essenti al as supplementation or fortification with folate is implemented.