Radiologic Issues

Fetal safety during diagnostic imaging is a primary goal for clinicians and patients. Significant radiation exposure may lead to chromosomal mutations, neurologic abnormalities, mental retardation, and an increased the risk of childhood leukemia. For acute indications, the benefits of the mother usually outweigh the small fetal risk. Radiation dosage is the most important risk factor, but fetal age at exposure is also important (41,42). Radiological exposure is measured using units of either rad or centiGrey (1 rad = 1 cGy). Fetal mortality is the greatest when exposure occurs within the first week of conception prior to oocyte implantation (41-43). The recommended radiation dose from approximately the first week of conception through week 25 is less than 5-10 rad (44). The most sensitive time period for central nervous system teratogenesis is between 10 and 17 weeks' gestation and nonurgent X-rays should be avoided during this time. In later pregnancy, the concern shifts from teratogenesis to increasing the risk of childhood hematologic cancer. The background incidence of childhood cancer and leukemia is approximately 0.2% to 0.3%. Radiation may increase that incidence by 0.06% per 1 cGy delivered to the fetus (44). Exposure of the fetus to 0.5 rad increases the risk of spontaneous abortion, major malformations, mental retardation, and childhood malignancy to one additional case in 6000 above baseline risk (41). Recommendations are that fetal risk is considered negligible at 5 rad or less and that the risk of malformation is

TABLE2 ■ Fetal Radiation Exposure from Diagnostic Imaging Studies

Study

Decreased

Chest radiograph

<0.001

Abdominal series

0.245

Pelvic radiograph

0.04

Upper gastrointestinal series

0.05-0.1

Barium enema

0.3-4

HIDA scan

0.15

Chest computed tomography scan

0.01-0.2

Abdominal computed tomography scan

0.8-3

Pelvic computed tomography scan

2.2

Source: From Refs. 29,41,140.

significantly increased at doses above 15 rad (29). The accepted cumulative dose of ionizing radiation during pregnancy is 5 rad with no single diagnostic study exceeding this maximum (Table 2) (41).

■ The American College of Radiology has stated that pregnant patients may undergo magnetic resonance imaging at any stage of pregnancy provided that the radiologist has a discussion with the patient regarding the risks of the study, the study cannot be delayed until delivery, and no other imaging modalities can provide the necessary information (47).

■ The American College of Radiology has stated that pregnant patients may undergo magnetic resonance imaging at any stage of pregnancy provided that the radiologist has a discussion with the patient regarding the risks of the study, the study cannot be delayed until delivery, and no other imaging modalities can provide the necessary information (47).

Recent large case series and one large retrospective review have demonstrated that pregnant patients may undergo laparoscopic surgery safely in any trimester without increased risk to the mother or fetus.

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