1. Radiation in pregnancy
CHA의대
강남차병원 산부인과
조연경

2. Definition (1)
• Roentgen (R): units of exposure
• Rad, Gray (Gy): absorbency into human tissue
– 100rad = 1Gy (gray) = 1 J/kg
• Rem, Sivert (Sv): biological effectiveness of absorbed
radiation
– 100rem = 1Sv

3. Definition (2)
• Relative biological effectiveness(RBE)
– correction factor for predicting the biological effect of absorbed
radiation
– 1 rem = 1 rad/RBE or 1 Sv = 1Gy/RBE
In radiation in soft tissue, RBE is about 1
 rad & rem (or Gy & Sv): used interchahgeably

4. Effects of radiation (1Gy)
prenatal exposure in rodents
Exposure group Preimplantation Embyo Fetus
Spontaneous ++ ± -
Abortion
Congenital - + -
Malformation
Intrauterine - + +
growth restriction
Mental - + +
retardation
(Schull WJ & Otake. 1999)

5. Effects of radiation exposure
Gestational age Weeks after Fetal dose Observed effects
conception
Preimplantation 0-2 0.05-0.1Gy Animal data:prenatal death
major 1-8 0.2-0.25 Gy sensitive stage for growth restriction
organogenesis
2-15 Small head size
< 8weeks :intellectual deficit (-)
Most sensitive time for induction of
childhood cancer
Rapid neuron 8-15 > 0.1 Gy Small head size, seizure, IQ point ↓
development and (↓25/0.1 Gy)
migration
After 15- term >0.1 Gy Increased frequency of childhood cancer
organogenesis and
rapid neuron
development
> 0.5 Gy Severe mental retardation (16-25 weeks)
(Schull WJ & Otake. 1999)

6. Ionizing radiation & malformation
Malformation Estimated threshold dose Gestational age at
greatest risk
Microcephaly > 20Gy 8-15 weeks
mental retardation 0.06-0.31Gy (8-15 weeks)
0.25-0.28 Gy (16-25 weeks) 8-15 weeks
> 0.5Gy (8-15 weeks)
Reduction of IQ 0.1 Gy 8-15 weeks
Other malformation > 0.2 Gy 3-11 weeks

7. Radiation and mental retardation
• 8-15 weeks,
: Risk of impaired CNS
development > 5 times
than 16~25 weeks
• < 8 weeks, or > 25 weeks
- No increased risk of
mental retardation

8. Cancer incidence (1950-1984) &
A-bomb radiation exposure
DS86 maternal uterine dose (Gy)
0 0.01-0.29 0.30-0.59 > 0.6
Mean dose (Gy) 0.000 0.087 0.416 1.372
No. at risk 710 682 129 109
Person –years 21770 21659 4095 3287
Cancer cases 5 7 3 3
Adjusted 22.4 32.5 77.8 97.0
rate/100,000
Estimated RR 1.00 1.24 2.18 4.78
[1.01-2.10] [1.06-6.32] [1.19-7.93]

9. Risks of leukemia in various groups
Group Approximate risk Increased risk over occurrence
control population
Siblings of leukemic 1/720 4 ~ 10 years
children
Gestational exposure 1/2000 1.5
U.S white children 1/2800 1
< 15 y.o.
(Brent RL, Teratology, 1986)

10. Estimated conceptus doses from
radiographic and fluoroscopic examinations
examinations Typical conceptus dose (mGy)
Cervical spine < 0.001
Extremities <0.001
Chest 0.002
T-spine 0.003
Abdomen
21cm patient thickness 1
33cm patient thickness 3
L-spine 1
Limited IVP 6
Small bowel study 7
Barium enema 7
(McCollough CH 2007)

11. Estimated conceptus doses from
single CT & Nuclear medicine exam
Examinations Typical conceptus doses (mGy)
Extra-abdominal
Head CT 0
Chest CT 0.2
Abdominal
Abdomen, routine 4
Abdomen/pelvis, routine 25
Early 1st trimester End of 1 st trimester
Bone scan 5 4
Whole body PET scan 15 10
Thyroid scan 0.2 0.1
(Pavlidis NA, 2002)

12. Probability of birth with no malformation
and no childhood cancer
Doses to conceptus No malformation No childhood No malformation
(mGy) (%) cancer(%) and childhood
cancer (%)
0 96.00 99.93 95.93
0.5 95.999 99.926 95.928
1.0 95.998 99.921 95.922
2.5 95.995 99.908 95.91
5.0 95.99 99.89 95.88
10.0 95.98 99.84 95.83
50.0 95.90 99.51 95.43
100.0 95.80 99.07 94.91
(Wagner LK 2002)

13. Spontaneous risk vs additional risk
Type of risk Spontaneous risk Additional risk
(0Gy exposure) from 0.05Gy
Spontaneous abortion 150,000/106 pregnancies 0
Major ongenital 30,000/106 pregnancies 0
malformation
Severe mental retardation 5,000/106 pregnancies 0
childhood leukemia/year 40,000/106 <?1-3/106year
pregnancies/year
prematurity 40,000/106 pregnancies 0
growth restriction 30,000/106 pregnancies 0
stillbirth 20-2,000/106 pregnancies 0
infertility 7% of couples 0

14. Cancer in pregnancy
Tumot type incidence
Breast cancer 1: 3,000-10,000
Cervical cancer 1.2 : 10,000
Hodgkin’s disease 1: 1,000-6,000
Malignant melanoma 2.6: 1,000
leukemia 1: 75,000-100,000

15. Ultrasonography
• Medical ultrasound: 1-20 MHz
• No independently confirmed significant biological effects in
mammals in low megahertz frequency range and < 100
mW/cm2
(American Institute of Ultrasound in Medicine, 1982)
• Largely replaced X-ray as the 1’ method of fetal Imaging
during pregnancy

16. Repeated Dx doses of x-ray/US :prenatal effect
Exposure Body weight Body length Head length Brain weight
groups
Control 1.25 ±0.010 25.62±0.094 8.10 ±0.042 0.086 ±0.001
X+U 1.22 ±0.012 25.38 ±0.012 8.08 ±0.041 0.085 ±0.001
U+X 1.20 ± 0.011* 25.12 ±0.201 8.07 ±0.046 0.086 ±0.001
X+X 1.22±0.015 25.34±0.188 8.09±0.040 0.086±0.001
U+U 1.19±0.013* 25.03±0.205* 7.97±0.045 0.083±0.001
(18-day mouse fetuses after repeated exposures to diagnostic doses of X-ray/US
during organogenesis)
(Hande MP, 1995)

17. Repeated Dx doses of x-ray/US :postnatal effect
Exposure groups Postnatal mortality Sex ratio % brain weight-
body weight ratio
Control 11.81 0.98 1.57±0.17
X+U 16.45 1.03 1.55 ±0.19
U+X 18.67 0.88 1.56±0.19
X+X 16.00 1.05 1.55±0.18
U+U 20.00* 0.94 1.45±0.18
(18-day mouse fetuses after repeated exposures to diagnostic doses of X-ray/US
during organogenesis)
(Hande MP, 1995)

18. Continuing a pregnancy after exposure
Gestational age Fetal absorbed dose
Control < 5 rad 5-15 rad > 15 rad
< 2 wk recommended recommended recommended
2-8 wk recommended
8-15 wk recommended
15 wk-term recommended recommended recommended
(Wagner LK, 1995)

19. Magnetic Resonance Imaging
• Magnet: alter the energy state of hydrogen protons
• Mice  eye malformation (Tyndall DA, 1991)
• Embryo is not sensitive to the magnetic field
(more studies are needed)
• But, Prudent to exclude pregnant women from MRI during the
1st trimester

20. Nuclear medicine
• Tc 99m
– brain, bone, renal, cardiovascular
– < 0.5 rad
• Ventilation-perfusion scan
– TechTc99m, 127Xe, 133Xe
– < 50 mrad
• Radioactive iodine
– Readily cross the placenta
– Adverse effect on fetal thyroid (esp. after 10-12weeks)
– Contraindicated during pregnancy
– If a diagnostic scan is essential, 123I or Tecnetium Tc99m

21. Contrast agent
• In CT, derivatives of iodine
– In animals, not teratogenic/Neonatal hypothyroidism
– Generally avoided unless essential for correct diagnosis
• Paramagnetic contrast agent (in MRI)
– In animals, abortion, skeletal/visceral abnormalities
(2-7 times the human dose)
• Should be used during pregnancy only if the potential benefit
justifies the potential risk

22. Paternal irradiation
• In Hiroshima & Nagasaki survivors,
→ No increase in malformation, fetal death, birth weight
• Father received diagnostic x-ray exam
→ Insignificant decrease in birth weight
(Avon Longitudinal Study of Pregnancy and Childhood)
• Association between paternal pre-conceptional radiational dose
and childhood leukemia has not been confirmed

23. Guidelines (1) : ACOG, 2004
• X-ray exposure from a single diagnostic procedure
does not result in harmful effects
• Concern about effect of high-dose ionizing radiation
exposure should not prevent indicated diagnostic X-
ray
• US / MRI
:not associated with known adverse fetal efects

24. Guidelines (2) : ACOG, 2004
• Consultation with an expert in dosimetry calculation
• Use of radioactive isotope of iodine is contraindicated
during pregnancy
• Radiopaque and paramagnetic contrast agent
: unlikely to cause harm

25. Abdominal radiation
in women of reproductive age
• Because the risk of 0.05 Gy is so small, the medical care of the mother take
priority over the risks to the embryo
• X-ray studies for diagnosis and treatment should not be postponed
• After diagnosis, elective procedure need not be performed on a pregnant
woman
• Other procedure can provide information without exposing to ionizing
radiation
• A period when the patient is pregnant but the pregnancy test is negative
– Risk: extremely small during this period of gestation
(all or none period)

26. Counseling patients
exposed to ionizing radiation
during pregnancy

27. Risk from ionizing radiation
• Spontaneous risks vs additional risks from low exposure of ionizing
radiation
• Diagnostic radiology (0.2 mGy-0.05Gy)
– Extremely low risk to the embryo
• >15%  spontaneous abortion
3%  major malformation
3%  IUGR (Brent RL , 1986)

28. Case 1
• Pregnant / possibly pregnant patient with clinical symptoms
– Should be performed at the time clinically indicated
– Should not be relegated to one portion of the menstrual cycle
In follow-up study(not an emergency),
– Postpone until the beginning of the next menstrual period

29. Case 2
• Patient has completed a diagnostic procedure that has exposed
her uterus to ionizing radiation
– Calculate dose to the embryo
• If < 5 rad, her risks have not been increased
• Threshold for birth defects > 0.2 Gy
– Determine stage of pregnancy

30. Case 3
• A woman delivers a baby with a serious birth defect
– Radiation induced malformation
: confined group of malformation
– < 0.05~0.1 Gy : not cause of the malformation
Analysis about dose, timing, nature of the malformation
– 15~25% of malformed children : genetic disease

31. Case 4
• When external radiation therapy / high exposures of
radionuclides
– Low exposure to embryo : Head, neck, upper chest, extremities
– Each radionuclides: different half-life, metabolism, excretion
– Expert evaluation to determine what the fetal exposure will be or
has been