Possible pregnancy complications secondary to maternal folate status may include spontaneous abortion, abruption placentae, congenital malformations (eg, neural tube defect), and severe language delay in the offspring. In a literature review, Ray et al examined 8 studies that demonstrated association between hyperhomocystinemia and placental abruption/infarction.  Folate deficiency also was a risk factor for placental abruption/infarction, although less statistically significant. 
Several observational and controlled trials have shown that neural tube defects can be reduced by 80% or more when folic acid supplementation is started before conception. In countries like the United States and Canada, the policy of widespread fortification of flour with folic acid has proved effective in reducing the number of neural tube defects. 
Although the exact mechanism is not understood, a relative folate shortage may exacerbate an underlying genetic predisposition to neural tube defects.
In a prospective observational study in Norway, where food is not fortified with folic acid, lack of supplementation with folic acid from 4 weeks before to 8 weeks after conception was associated with increased risk of severe language delay in the child at age 3 years.  No association between folic acid supplementation and gross motor skills was reported.
A more recent Norwegian prospective cohort study reexamined the maternal use of supplemental folic acid prior to and during pregnancy and demonstrated an association between child autism and lack of supplementation. There was no association between maternal folic acid supplementation and child Asperger syndrome or pervasive developmental disorder-not otherwise specified.