1. The document outlines guidelines for diagnostic imaging during pregnancy, dividing fetal development into three phases: pre-implantation, major organogenesis, and fetal development. 2. It provides threshold doses of radiation for potential biological effects on the fetus such as abortion, organ malformation, growth retardation, and mental impairment. The risks are negligible below 5 rads. 3. Estimated radiation doses are provided for various diagnostic x-ray exams and CT scans, with abdominal CT posing the highest risk at over 1 rad and requiring only 1-2 scans to reach the 5 rad threshold. 4. Guidelines recommend that medically necessary x-rays below 5 rads are safe, and ultrasound and MRI which have

1. Guidelines for Diagnostic
Imaging During Pregnancy

2. Stages of Fetal Development
Development of the unborn child is expressed as
postconception age and can be divided
approximately into three major phases:
1. The pre-implantation/implantation phase
0–2 wk, from conception to implantation
2. The phase of major organogenesis
3rd–8th wk
3. The phase of fetal development
from 9th weeks until birth

3. Risks and Threshold Doses of the
Main Effects of Prenatal Irradiation
Gestational
Age
Stage
Potential
Biologic Effect
Threshold Risk
0–2 wk
Preimplantation
/implantation
Abortion >10 rad
Organ
malformation
>5; >10 rad
3–7 wk Organogenesis
Growth
retardation
>10 rad
8–25 wk Fetal
Growth
retardation
>10 rad
Mental
impairment
>10 rad
Whole
pregnancy
Carcinogenesis None 6 ? 10−4 per rad
Mutagenesis None 1 ? 10−2 per rad
Modified from Fattibene P,Mazzei F,Nuccetelli C, Risica S: Prenatal exposure
to ionizing radiation: Sources, effects, and regulatory aspects. Acta Paediatr
88:693, 1999.

4. Estimated Fetal Exposure for Diagnostic Images
Examination Type
Estimated Fetal Doseper
Examination (rad)
Number of Examinations
Required for Cumulative5-
rad Dose
Plain Films
Skull 0.004 1,250
Dental 0.0001 50,000
Cervical spine 0.002 2,500
Upper or lower extremity 0.001 5,000
Chest (2 views) 0.00007 71,429
Mammogram 0.020 250
Abdominal 0.245 20
Thoracic spine 0.009 555
Lumbosacral spine 0.359 13
Intravenous pyelogram 1.398 3
Pelvis 0.040 125
Hip (single view) 0.213 23

5. Estimated Fetal Exposure for Diagnostic Images
Examination Type
Estimated Fetal Doseper
Examination (rad)
Number of Examinations
Required for Cumulative5-
rad Dose
CT Scans (Slice Thickness: 10 mm)
Head (10 slices) <0.050 >100
Chest (10 slices) <0.100 >50
Abdomen (10 slices) 2.600 1–2
Lumbar spine (multiple
views)
3.500 1–2
Pelvimetry (1 slice with
scout film)
0.250 20

6. Key Statements on Diagnostic Imaging
Modalities during Pregnancy
X-Ray Imaging
Magnetic Resonance Imaging
Ultrasound Imaging

7. X-Ray Imaging
“No single diagnostic procedure results in a
radiation dose that threatens the well-
being of the developing embryo and fetus.”
American College of Radiology;
Scientific view of low-level radiation risks.
Radiographics 11:509, 1991.

8. “ Fetal risk is considered to be negligible at 5
rad or less when compared to the other
risks of pregnancy, and the risk of
malformations is significantly increased
above control levels only at doses above
15 rad.”
National Council on Radiation Protection and Measurements;
Medical Radiation Exposure of Pregnant and Potentially Pregnant Women.
NCRPM Report No. 54. Bethesda, MD, NCRPM, 1977.

9. “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 has
not been associated with an increase in fetal
anomalies or pregnancy loss.”
American College of Obstetricians and Gynecologists,
Committee on Obstetric Practice;
Guidelines for Diagnostic Imaging During Pregnancy.
ACOG Committee Opinion No. 299.
ACOG, September 2004.

10. Magnetic Resonance Imaging
“Although there have been no documented
adverse fetal effects reported, the National
Radiological Protection Board arbitrarily
advises against its use in the first trimester.”
American College of Obstetricians and Gynecologists,
Committee on Obstetric Practice;
Guidelines for Diagnostic Imaging During Pregnancy.
ACOG Committee Opinion No. 158.
ACOG, 1995.

11. Ultrasound Imaging
“There have been no reports of documented adverse
fetal effects for diagnostic ultrasound procedures,
including duplex Doppler imaging.”
“There are no contraindications to ultrasound
procedures during pregnancy, and this modality
has largely replaced x-ray as the primary method
of fetal imaging during pregnancy.”
American College of Obstetricians and Gynecologists,
Committee on Obstetric Practice;
Guidelines for Diagnostic Imaging During Pregnancy.
ACOG Committee Opinion No. 299.
ACOG, September, 2004.

12. Guidelines for Diagnostic Imaging
during Pregnancy
American College of Obstetricians and Gynecologists.
ACOG Committee Opinion No. 299.
Obstet Gynecol 2004;104:647–51.

13. Women should be counseled that x-ray
exposure from a single diagnostic procedure
does not result in harmful fetal effects.
Specifically, exposure to <5 rad has not been
associated with an increase in fetal
anomalies or pregnancy loss.

14. Concern about possible effects of high-dose
ionizing radiation exposure should not
prevent medically indicated diagnostic x-ray
procedures from being performed on a
pregnant woman.
During pregnancy, other imaging procedures
not associated with ionizing radiation
(ultrasonography and MRI) should be
considered instead of x-rays when
appropriate.

15. Ultrasonography and MRI are not
associated with known adverse fetal
effects.

16. Consultation with an expert in dosimetry
calculations may be helpful in calculating
estimated fetal dose when multiple
diagnostic x-rays are performed on a
pregnant patient.

17. The use of radioactive isotopes of iodine is
contraindicated for therapeutic use during
pregnancy.

18. Radiopaque and paramagnetic contrast
agents are unlikely to cause harm and
may be of diagnostic benefit, but these
agents should be used during pregnancy
only if the potential benefit justifies the
potential risk to the fetus.