OB and X-rays
                          =============

þ X-ray effects on fetus
 - Fetal exposure to 1 rad (1000 millirads) of radiation is
   associated with a 1/1000 risk of fetal anomaly.
   Ref: Rosen 3rd ed. p 1999
 - at 15,000 millirads, start seeing mental retardation, childhood
   malignancies, and microcephaly.
 - fetus most sensitive during organigenesis:  before 9 weeks.
 - little risk if beam directed more than 10 cm away from fetus.

þ X-ray dosages (in millirads = mR)
 - skull                   1 mR
 - cervical spine          1 mR
 - thoracic spine          1 mR
 - chest                   5 mR
 - femur                   50 mR
 - extremities             1 mR each
 - lumbar spine            300 mR
 - hip                     370 mR
 - IVP                     900 mR
 - abdomen                 200 mR
 - CT head or chest        1000 mR
 - CT abdomen to 2 cm above
     uterus                3000 mR
 - CT abdomen and pelvis   3000-9000 mR
   Ref: Rosen 3rd ed. p 1999