Exposure to folic acid antagonists up until this many days/weeks after conception may inhibit neural tube closure.
What is 28 days/4 weeks? e.g. Carbamazepine, valproic acid, and methotrexate
This is the mechanism underlying maternal hypotension in the setting of regional anesthesia.
What is sympathetic blockade? -It occurs after about 10% of spinal or epidural blocks given during labor -result of the effects of local anesthetic agents on sympathetic fibers, which normally maintain blood vessel tone. -Vasodilation results in decreased venous return of blood to the right side of the heart, with subsequent decreased cardiac output and hypotension
This is the upper limit of radiation exposure recommended during pregnancy.
What is 5 rads? -exposure less than 8 weeks results in the “all or none effect”, with an increased risk of an SAB and no increased -exposure between ~8-15 weeks presents the highest risk of anomalies (e.g. microcephaly, cognitive delay, and IUGR) -this is based on data from pregnant women who survived the Nagasaki and Hiroshima attacks that showed ~ 50 rads or more of exposure resulted in the greatest increased risk
The following pattern of anomalies: oral cleft, growth restriction, microcephaly, hypoplasia of digits and nails, short nasal bone, and urogenital anomalies is associated with prenatal exposure to this medication.
What is Phenytoin? -up to 10% of infants prenatally exposed to Phenytoin will demonstrate fetal hydantoin sydrome