Book of Medical Disorders in Pregnancy - Tintash

3.19, 1.29 and 1.30, respectively [10].
However, this may be an artifactual
result, since radiographic studies in the
first trimester may have included a
disproportionately high fraction of high
dose non-obstetric studies such as IVPs
and barium enemas. Also, experimental
work in dogs suggests exposure later in
gestation is more carcinogenic.
None-theless, the possibility of premalignant
change in the first trimester
remains, leading the NRPB to assume
that some risk exists after irradiation in
the first weeks of pregnancy. Assuming
a rela-tively high fetal dose estimate of 5
rads for a pelvic CT during pregnancy,
the relative risk of fatal childhood cancer
may be doubled. This relative risk may
appear substantial, but it should be
remembered that the baseline risk is very
low, so that the odds of dying of
childhood cancer go from 1 in 2000
(baseline) to 2 in 2000 (after 5 rads). To
assist with patient counseling, some
practical risk comparisons may be
helpful. The excess risk (of 1 in 2000) is
equivalent to driving 20,000 miles in a
car or living in New York City for 3
years. It should also be noted that the
guidelines of the American College of
Obstetricians and Gynecologists are
superficial in their discussion of the
carcinogenic risk of radiation during
pregnancy, describing it as "very small"
and concluding "abortion should not be
recommended". The ACOG guidelines
do not indicate what information or risk
estimates should be provided during
parental counseling, if any. CT of the
fetus should be avoided in all trimesters
of pregnancy, because it may cause up to
a doubling of the risk of fatal childhood
cancer.
219
Avoiding exposure in pregnancy: No
law or professional standard requires
that radiologists determine in advance
whether a patient of childbearing age is
pregnant. However, it is clearly good
practice to implement the following guidelines:
Signs should be prominently displayed
in all radiology departments asking each
patient to notify a technologist or physician
if she is, or thinks she could be,
pregnant. All technologists should ask
women of childbearing age if they might
be pregnant prior to performing a
radiologic procedure. Radiology requisition
forms filled out by referring physicians
should include a section dealing
with the possibility of pregnancy. No
radiological procedure involving exposure
to the pelvis should be undertaken
in a patient who declares she may
be pregnant without consultation with a
radiologist. The radiologist should
discuss risks and benefits with the
patient, and determine if it is appropriate
to proceed, perform an alternative
procedure, or delay the study to allow
performance of a pregnancy test. It
should be noted that current
recommendations do not recognize a
safe period during the menstrual cycle,
and so the concept of the "ten day rule"
is obsolete.
A patient who thinks she may be
pregnant should be discussed with the
referring physician, in order to determine
the appropriate course of action (e.g.,
rescheduling after pre-gnancy testing,
proceeding with the test after counseling,
or changing to another modality). It is
the responsibility of the patient to
disclose any possibility of pregnancy,
although appropriate sign-age and
questioning of all women of