herpes virus), spirochetes (e.g., syphilis), and protozoa (e.g., toxoplasmosis).
Ionizing radiation: No single diagnostic procedure results in radiation
exposure to a degree that would threaten the developing pre-embryo, embryo,
or fetus. No increase is seen in fetal anomalies or pregnancy losses with
exposure of <5 rads. The greatest risk of exposure is between 8 and 15 weeks'
gestation with the risk of nonthreshold, linear function at doses of at least 20
rads.
Chemotherapy: Risk is predominantly a first-trimester phenomenon.
Second- and third-trimester fetuses are remarkably resistant to
chemotherapeutic agents.
Environmental: Tobacco is associated with intrauterine growth restriction
(IUGR) and preterm delivery, but no specific syndrome. Alcohol is associated
with fetal alcohol syndrome: midfacial hypoplasia, microcephaly, intellectual
disability, and IUGR.
Recreational drugs: Cocaine is associated with placental abruption, preterm
delivery, intraventricular hemorrhage, and IUGR. Marijuana is associated
with preterm delivery but not with any syndrome.
Medications (account for 1–2% of congenital malformations): The ability of
a drug to cross the placenta to the fetus depends on molecular weight, ionic
charge, lipid solubility, and protein binding. Drugs are listed by the FDA as
category A, B, C, D, or X.
kiana
(Kiana)
#1