Effects of Radiation Exposure on the Developing Fetus

Hannah Connolly, Janessa Gioia, Gillian Reid, Nadine Savoie, Suzanne Taylor

University of New Brunswick

Problem Statement Pregnant women may be denied diagnostic and therapeutic

radiation procedures because physicians fear the radiation will cause harm to the developing fetus. Thus, fewer options are available for improving the health of pregnant women when they require medical attention. Understanding the effects of radiation on the developing fetus may help physicians better counsel their patients on the risks involved. This education would allow for an informed decision to be made on whether to proceed with radiation procedures.

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Research Question

Are diagnostic and therapeutic radiation procedures harmful to the developing fetus?

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Harmful Teratogenic- causing congenital malformations

Carcinogenic- cancer causing

Mutagenic- causing genetic changes

(Whitt, 2010)

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Related Diseases

Major Mutations

Other abnormalities

The major risk is of course, embryonic loss. (Brent 1999).

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Radiation: DNA Damage

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History of why these studies emerged

Hiroshima and Nagasaki, Chernobyl

In 1956: prenatal exposure to radiation from diagnostic X-ray (Naumburg et al. 2001; Doll & Wakeford, 1997)

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Fetal Stages and Radiation Sensitivity

(1) Preimplantation (days 0 to ~14)

(2) Organogenesis (week 2 to week 8)

(3) Fetal (week 9 to term)

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Methods Quantitative

Experimental

Non Experimental

Retrospective

Prospective

Surveys

Time frames

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Health Concerns From our studies these are some health concerns that would bring

pregnant woman to our departments

Pulmonary Embolism

Loss of bone density

Cancer

Abdominal/Pelvic issues

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Pulmonary Embolism

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Pulmonary Embolism Chest X-ray + V-P Scan + Helical CT + Pulmonary Angiograpy with brachial

approach = ~ 1000 uGy.

Ventilation perfusion scans:

The presence and absence of PE is inconclusive in up to 80% of these scans

Prior episodes of PE may cause a false-positive result (Winner-Muram et al., 2002)

Fetal dose > 10 cGy, the probability of congenital defects rises 10%. (Tutty, 2001)

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Bone Density

There is evidence that some pre-existing disorders as well as heparin treatments may lead to significant diminution of bone mass during pregnancy.

Treatment would be administered to patients who demonstrate rapid bone lose during the first postconception months.

Emryo/fetus doses were found to be lower than the average daily natural background from a proximal femur scan. 

Benefits Outweigh Risks! (Damilakis, 2002)

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Abdominal and Pelvic Procedures

Medical imaging such as CT may be required of the abdominal/trunk/pelvic area due to trauma, acute abdominal pain, appendicitis, or renal issues in a pregnant patient.

Ultrasound

Survey respondents are more likely to choose CT for trauma in all three trimesters.

For acute abdominal indications they were more likely to choose CT in the second and third trimester, and MRI in the first trimester.

The trend found in radiology literature is that CT is fast, readily available and allows immediate surgical intervention if needed. (Jaffe,

2007)Retrieve from http://www.lakeridgehealth.on.ca/patient_care/interventional_radiology/presentations/radiology/slide25.htm

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Abdominal and Pelvic Procedures

Literature suggests that for most radiologic procedures, the risk of fetal demise in the first 2 weeks after conception is less than 1% (Jaffe, 2007).

Radiologists may also opt for a modified CT protocol to reduce the exposure by reducing the power of the x-rays (kVp or mAs) (Damilakis et al., 2000).

No direct radiation to the fetus. (Hurtwitz et al. 2006; Kal & Struikmans, 2005)

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Cancer Diagnosis & Treatment when Pregnant

Cancer: 1 per 1000 pregnancies (Kal & Struikmans, 2005; Pavlidis & Penteroudakis, 2005)

Most common cancer types (Greskovich & Macklis, 2000; Pavlidis & Penteroudakis, 2005).

Carcinoma of the cervix: is the most common Breast cancer pregnant patient 1 in 3000 (Berry et al. 1999; Greskovich & Macklis, 2000; Kal & Struikmans,

2005; Pandit-Taskar et al. 2006)

Radiation therapy is not usually offered during pregnancy (Pavlidis & Penteroudakis, 2005; Kal & Struikmans, 2005)

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Diagnosing Oncology Patients

To diagnose:

Fine-needle biopsy, ultrasound, mammography, MRI (Berry

et al. 1999; Greskovich & Macklis, 2000; Pavlidis & Penteroudakis, 2005; Kal & Struikmans, 2005, Hurtwitz et al., 2006; Doll & Wakeford, 1997; Nicklas & Baker, 2000)

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Delaying Radiation

All chemotherapy drugs: crossing the placenta.

The first trimester: spontaneous abortion.

ethical balance must be achieved (Pavlidis &

Penteroudakis, 2005; Kal & Struikmans, 2005).

Delaying treatment until the second and third trimester. (Greskovich & Macklis, 2000; Pavlidis &

Penteroudakis, 2005, Doll & Wakeford, 1997; Departement of Health and Human Services, 2005).

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Staging for Oncology Patients

The benefits vs. risks(Greskovich & Macklis, 2000; Osei & Faulkner, 2000).

Main concerns of doctors (Pavlidis & Penteroudakis, 2005).

The medical staff and patient need to decide as a team whether to begin treatment or to postpone it (Kal & Struikmans, 2005).

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How much radiation is to much?

It is concluded that radiation doses of the order of 10 mGy received by the fetus in utero produce a consequent increase in the risk of childhood cancer. (Doll & Wakeford, 1997)

Lymphoscintigraphy for sentinel lymph node mapping (SLN) led to a neglible dose to the fetus (0.014 mGy or less) (Pandit-Taskar, 2006).

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Oncology Studies

Relative risk are higher: first (Greskovich & Macklis, 2000; Pavlidis & Penteroudakis, 2005; Doll, & Wakeford, 1997;

Department of Health and Human Services, 2005). Mastectomy with postpartum radiation (Berry et al. 1999)

Patients received a median of four cycles of chemotherapy (Berry et al. 1999; Doll, & Wakeford, 1997; Department of Health and Human Services, 2005).

Neonates: no unusual complications or malformations. (Berry et al. 1999)

Fetal dose was much less than the NCRP limit. Pandit-Taskar et al. (2006)

Oncology- Thyroid Cancer

Radioiodine (131I) Therapy Abnormalities Indirect exposure to: the uterus, 131I uptake in the

blood, bladder, gut, kidneys Within a year after the therapy: miscarriages and

induced abortions. A number of stillbirths after radioiodine therapy:

high. Thyroid hormone DO NOT: conceive one month prior the therapy and

postponing conception until the thyroid hormone status has been verified.

(Garsi, J-P., et al. 2008, Bohuslavizki, 1999)

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Childhood Development

Preschool aged children

No damaging effects of diagnostic imaging, low dose x-radiation. (Ornoy et al., 1996)

Large radiation doses (Department of Health and Human Services, 2005)

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Childhood Cancer

The USNCRP: doses of 50 mGy or less is negligible

Baseline risks

However…

increases in use of of CT and nuclear medicine radiodiagnostic procedures

Inadvertent exposure in early pregnancy may occur

(Ratnapalan et al., 2003; Ray et al. 2010)

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Childhood CancerLeukemia

Leukemia is the most common malignancy among children.

Study: children born in Sweden between 1973- 1989.

Association between leukemia and diagnostic x-rays is likely to be small.

(Naumburg et al., 2001)

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Childhood CancerMalignancy

Ontario study: Between April 1, 1992 and March 31, 2008.

Researchers looked at the incidence of malignancy in those children

Exposed mothers vs. unexposed mothers

They concluded: no difference noted

(Ray et al., 2010)

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 Perception of the Risks

Ontario survey

Misperceptions of physicians

Could lead to anxiety, delay of care among pregnant woman (Ratnapalan et al., 2004)

Misperception of patients may be caused by misinformation (Bentur et al. 1991)

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Recommendations & Precautions

Menstrual Cycle (Vollman, 1977; Zanotti-Fregonara et al. 2009)

Modify daily procedures ALARA- as low as reasonably achievable Radiation Therapy Do treatment planning and risk management. (Bednarz & Xu, 2008).

Lead shielding (Sechopoulos et al. 2008) http://www.youtube.com/watch?v=eziUXYwl_Cs

Serum testing (Ray et. al, 2010)

MRI and Ultrasonography Bone densitometry on a pregnant patient Physician education (Ratnapalan et al., 2004)

Brief counseling Pregnant nuclear workers  (Damilakis et al. 2005)

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Limitations Randomization

Small sample size

The use of phantoms instead of real-life subjects.

Phantom does not take into account all different body variation

Retrospective designs

Results are only approximations.

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Conclusion The amount of radiation absorbed by the fetus varies

Misperceptions exist

2 most important determining factors : dose & stage of gestation

The effects of radiation may be harmful: threshold value of 50 mGy

ALARA

Benefits outweigh risks

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References