Imaging During Pregnancy

Imaging and Radiation Exposure During Pregnancy

Imaging during pregnancy poses special challenges. At times, imaging can provide valuable – even life-saving – information, but at certain phases of pregnancy, imaging with x-rays may pose risk to a developing fetus. This paper provides information and known risks about common imaging studies during pregnancy.

First, the most common imaging during pregnancy uses ultrasound which has no known risk of fetal developmental delay or congenital anomaly. This modality is utilized throughout the world for imaging and measurements during pregnancy.

Second, Magnetic Resonance Imaging (MRI) may occasionally be performed to address special questions regarding suspected fetal anomaly. There have been no documented fetal anomalies or growth problems following MRI; however, as a precaution, this modality is generally not performed in the first trimester during the phase of rapid fetal development.

Most concern and questions arise concerning exposure of a developing fetus to x-rays. X-ray exposure may result from an essential test during pregnancy or inadvertently during early and unexpected pregnancy. Generally physicians’ goal is to avoid exposing pregnant mothers and fetuses to x-rays. However, this is balanced against the occasional need to obtain information crucial to the health and well-being of a mother or fetus that can only be obtained by a radiologic study.

The information below gives typical fetal exposure for common maternal imaging studies. The absorbed dose – measured in milliSievert (mSv) – is a measure of the energy absorbed from ionizing radiation per kilogram and gives some idea of the relative risk to the fetus.

Type X-ray for Pregnant Mother	Fetal Exposure (mSv)
Natural Background	0.9
Chest X-ray	0.0007
Mammogram	0.2
AP Pelvis	1.3
AP Thoracic Spine	0.1
AP Lumbar Spine	1.97
Extremity	0.01
Upper GI	0.6
Barium Enema	40
IVP	14
CT Head	0.5
CT Chest	0.1
CT Abdomen / Pelvis	26

No direct evidence confirms either cancer or birth defects from exposure to diagnostic x-rays, but scientists and physicians cautiously assume that there may be some effect even from low level exposure and estimate risk from those who have had very large exposures such as atomic blast victims. A cautious estimate for lifetime cancer or leukemia risk to a child exposed to an abdominal CT exam is 0.1-0.2%. Since the lifetime cancer risk in the U.S. is 23%, this means that the risk is increased to approximately 23.2%. The increased risk from CT is very small.

Potential risks of fetal malformation depend upon the stage of fetal development at the time of exposure:

1 - 2 weeks post conception	No risk. High dose exposure can result in spontaneous abortion. Surviving pregnancies are normal.
3 – 10 weeks	Organogenesis phase with greatest risk of of malformation with threshold 50-250 mSv.
10-15 weeks	Decreased risk of malformation. Possible microcephaly/mental retardation at doses >120 mSv
>15 weeks	No risk except growth restriction or mental retardation at very high doses (much higher than in x-ray imaging)

Therefore, women exposed to less than 50 mSv have indistinguishable pregnancy outcomes to those exposed only to background radiation (spontaneous abortion ~15%, major malformation ~3%, intrauterine growth retardation ~4%). It is generally recommended that the cumulative fetal dose during pregnancy remain less than 50 mSv (5 rad).

In general, pregnant mothers should avoid exposure to x-rays whenever possible without jeopardizing their health or the health of their fetus. In some cases, the information from a radiologic exam may be critical. The American College of Obstetricians and Gynecologists stated: “Women should be counseled that x-ray exposure from a single diagnostic procedure does not result in harmful fetal effects. Specifically, exposure to less than 5 rad [50 mSv] has not been associated with an increase in fetal anomalies or pregnancy loss.” The risk of fetal malformation occurs only during the period from two to 15 weeks after conception.

You may ask our technical staff or radiologists for further information about radiation. Always inform the receptionist or technologist prior to x-ray if there is any chance you are pregnant. More information about radiation exposure from common x-ray procedures is found on the department link “Radiation Exposure in Radiology” and in internet references:

Safety of Imaging in Pregnancy #1
Safety of imaging in Pregnancy #2

M. Rizzo 10/2/05

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