A 24-year-old woman is in a car accident and is taken to an emergency room, where she receives a chest x-ray and a film of her lower spine. It is later discovered that she is 10 weeks pregnant. She should be counseled that
A. The fetus has received 50 radsB. Either chorionic villus sampling (CVS) or amniocentesis is advisable to check for fetal chromosomal abnormalities
C. At 10 weeks, the fetus is particularly susceptible to
derangements of the central nervous system
D. The fetus has received less than the assumed threshold for radiation damage.
Ans: The
answer is d.While
a 50-rad exposure in thefirst trimester of pregnancy would be expected to
entail a high likelihood of serious fetal damage and wastage, the anticipated
fetal exposure for chest x-ray and one film of the lower spine would be less
than 1 rad. This is well below the threshold for increased fetal risk, which is
generally thought to be 10 rads. High doses of radiation in the first
trimester primarily affect developing organ systems such as the heart and
limbs; in later pregnancy, the brain is more sensitive. The chromosomes are
determined at the moment of conception. Radiation does not alter the karyotype,
and determination of the karyotype is not normally indicated for a 24-year-old
patient. The incidence of leukemia is raised in children receiving radiation
therapy or those exposed to the atomic bomb, but not from such a minimal
exposure as here
