Table 1.

Summary of Overlapping Patterns of Risk for NTDs and Schizophrenia

	NTDs	Schizophrenia
Famine studies	↑ risk in offspring of women pregnant during Dutch and German famines	↑ risk in offspring of women pregnant during Dutch and Chinese famines
Temporal trend	↓ incidence over past few decades	Some evidence of ↓ incidence over past few decades
Season of birth effects	Some evidence of ↑ risk in spring-summer conceptions (winter-spring births)	↑ risk in winter-spring births
Maternal febrile/flu-like illness	↑ risk	↑ risk
Raised maternal BMI	Some evidence of ↑ risk	Some evidence of ↑ risk
Maternal diabetes	Some evidence of ↑ risk	Some evidence of ↑ risk
Short birth spacing interval	Some evidence of ↑ risk	Some evidence of ↑ risk
Parity	Some evidence that multiparity and primiparity both ↑ risk	Some evidence that multiparity and primiparity both ↑ risk
MTHFR C677T genotype	↑ risk in both maternal and fetal TT homozygotes	↑ risk in TT homozygotes
Homocysteine	↑ risk in maternal hyperhomocysteinemia	↑ risk in subjects with hyperhomocysteinemia

Note: NTDs, neural tube defects; BMI, body mass index; MTHFR, methylenetetrahydrofolate reductase.