scope:
NCRP Report No. 174, Preconception and Prenatal Radiation
Exposure: Health Effects and Protective Guidance, updates and
expands the National Council on Radiation Protection and
Measurements (NCRP) Report No. 54, Medical Radiation Exposure of
Pregnant and Potentially Pregnant Women (1977). Scientific
knowledge has increased and public concerns have changed in the 36
y since NCRP Report No. 54 was published. The scope of NCRP Report
No. 174 covers both ionizing radiation sources and specific
nonionizing sources [i.e., magnetic-resonance imaging (MRI),
ultrasound imaging, and radiofrequency (RF) fields]. This Report
provides information on the types, sources and magnitudes of
ionizing radiation exposures of reproductive relevance. Ionizing
radiation exposures from medical care (diagnostic and therapeutic
procedures, including radiopharmaceuticals) are addressed as well
as from occupational sources, common environmental exposures, and
from accidental or deliberate (e.g., a terrorist act) releases of
radionuclides. The ionizing radiation sources discussed consist
predominantly of low linear energy transfer (LET) radiation (e.g.,
x rays from prenatal medical procedures). The risks from ionizing
radiation exposure are examined in detail from preconception
through pregnancy, and during the nursing of infants. Outcomes and
associated risks from preconception exposure that were evaluated
include: infertility, stillbirths, birth defects, genetic
alteration, and cancer. Outcomes and associated risks from exposure
during pregnancy that were evaluated include: congenital
malformations, growth retardation, embryonic and fetal death,
mental retardation and neurobiological effects, and cancer. Also
discussed is the risk to the nursing infant from the transfer of
radioactive material through the mother's milk (e.g., milk from a
mother who received a radiopharmaceutical) as well as from direct
exposure due to radionuclides present in the mother's body. Methods
for managing dose and reducing risk from various medical procedures
are also addressed. For nonionizing sources (MRI, ultrasound
imaging, and RF fields), the focus is on prenatal exposure, with
limited coverage of childhood and adult exposure. Outcomes and
associated risks during pregnancy that were evaluated, as relevant
to exposure from a particular nonionizing source, include: low
birth weight, delayed speech, dyslexia, nonright-handedness, and
impaired intellectual performance.
