What supplements can i take to reduce pregnancy complications?

Folic acid!: Take Folic Acid 1-5 mg daily by mouth to prevent up to 95% of fetal neural tube defects (spina bifida, anencephaly, encephaloceles) and up to 75% of fetal cardiac defects (vsds, tetralogy of fallot, hypoplastic left heart syndrome, etc), while preventing preterm birth by up to 40% (see bukowski r et al from faster trial consortium on new england of medicine)!