1、Radiation in PregnancySehra SampsonMS 4 OHSUFetal DevelopmentnEmbryonic Period:first day of last menstrual period through the 9th week,includes organogenesisnFetal Period:10th week through birthRadiationnRadiation quantities and units The new unit of dose is the gray(Gy,1 Gy=100 rad).In diagnostic r
2、adiology,doses are small and are generally expressed in millirads(1 mrad=0.001 rad)or micrograys(1 mGy=0.000001 Gy).nWhat is a rad?the amount of energy deposited per kilogram of tissuenWhat is the usefulness of“rads”?to compare the radiation dose in different exposures.nNatural background exposure a
3、t sea level is about 300 mrad per year.Radiation and Fetal DevelopmentnThe maximal limit of ionizing radiation to which the fetus should be exposed during pregnancy is a cumulative dose of 5 rad.Radiation and Fetal DevelopmentnFetal risk is considered to be negligible at 5 rad or less when compared
4、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.NCRP Report no.54.Bethesda,Md.:The
5、 Council,1977.Exposure CategoriesnTeratogenesis or fetal malformationnCarcinogenesis or induced malignancynMutagenesis or alteration of germ-line genesExposure TeratogenesisnThe most common fetal malformations caused by high-dose radiation are of the central nervous system,primarily microcephaly and
6、 mental retardation.nOnly shown in cases where fetus was exposed to 10-150 rad,particularly before 10 weeks gestation.Exposure-TeratogenesisnThe risk of birth defects such as malformation of the lips,mid-face,teeth,or external genitalia are greatest with exposures of 5-25 rads between 3-10 weeks ges
7、tation.nThe risk of birth defects or malformations decreases considerably after the 10th week of gestation.Exposure CarcinogenesisnExposure to as little as 1-2 rad has been associated with a slight increase in childhood malignancies,especially leukemia.Incidence of leukemia in exposed children is ab
8、out 5 per 10,000.nGeneral incidence of childhood leukemia is about 3.6 per 10,000 Exposure MutagenesisnExposure to radiation may increase the frequency of germ-line mutations that occur naturally in the general population.nThe exposure dosage required to double this baseline mutation rate is between
9、 50-100 rad.Imaging in PregnancynRadiating procedures X-Ray CT Scan Nuclear Medicine FluoroscopynNon-radiating procedures MRI UltrasoundnDiagnostic radiologic procedures should not be performed during pregnancy unless the information to be gained from the study is necessary for the care of the patie
10、nt.X-ray imagingnSingle diagnostic procedures do not result in radiation doses that will be harmful to the developing embryo or fetus.nWomen 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 ha
11、s 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.158.Washington,D.C.:ACOG,1995CT ScannConsidered a secondary te
12、st given risks of radiation exposure to fetusnACOG(American College of Obstetrics/Gynecology)Recommendations if imaging is required:Chest/Head CT:Safe since total dose 1 rad Abd/Pelvis:Safe if only to be tested once:total dose:3.5 rad Pelvis only:Safe total dose 250 mrad.Nuclear Medicine StudiesnUse
13、 accepted radiopharmaceutical conceptus dosenKeep exposure of radionuclides to a minimum.Certain radiopharmaceuticals,such as 131-I and 32-P,rapidly cross the placenta.nChoose an alternative test if appropriatenMost radiopharmaceuticals will be expressed in breast milk.Avoid 131-I in the nursing mot
14、her.FluoroscopynUse accepted radiopharmaceutical conceptus dosenMinimize exposure time to patient and fetus especially if study is in abdomen or pelvisCommon diagnostic procedures and associated radiation dosenKEVIN S.TOPPENBERG,M.D.,D.ASHLEY HILL,M.D.,and DAVID P.MILLER,M.S.Safety of Radiographic I
15、maging During Pregnancy.American Family Physician.April 1999 Magnetic Resonance ImagingnConsidered a preferential test to CT to avoid ionizing radiation Gadolinium should be avoided during the 1st trimesternRapid sequence MR imaging is preferred to conventional MR imaging because of briefer exposure
16、nStudies show efficacy in MR studies of right sided abdominal pain(cholecystitis,appendicitis)Magnetic Resonance ImagingnAlthough there have been no documented adverse fetal effects reported,the National Radiological Protection Board arbitrarily advises against its use in the first trimester.-Americ
17、an College of Obstetricians and Gynecologists,Committee on Obstetric Practice.Guidelines for diagnostic imaging during pregnancy.ACOG Committee opinion no.158.Washington,D.C.:ACOG,1995Ultrasound ImagingnConsidered the preferred imaging modality in pregnancynSensitivity of study depends on patient an
18、atomy and operator techniqueUltrasound ImagingnThere 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
19、 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.158.Washington,D.C.:ACOG,1995Patient Counseling nThe American College of Obstetricia
20、ns and Gynecologists has stated that exposure to X-rays during a pregnancy is not an indication for therapeutic abortion.nRisk for teratogenesis and carcinogenesis in the general population is approximately 286 per 1,000 deliveries.Exposure of 0.5 rad to a fetus adds,to the general risk,about 0.17 c
21、ases per 1,000 deliveries.Patient CounselingnNursing mothers:Breastfeeding must be terminated during treatment with 131-I.For all other radiopharmaceuticals,the rule of thumb is to“pump and dump”for 24 hours after exposure.Limit physical exposure to child during and shortly after exposure to mother.
22、Patient CounselingnAlthough diagnostic procedures are very low risk to the fetus,it is important never to promise the parents a“perfect baby”.nWhen a diagnostic study is needed for management of a pregnant woman,the American College of Radiology recommends that health care workers should tell patien
23、ts that x-rays are safe and provide patients with a clear explanation of the benefits of the exam regarding their care.ConclusionnMaximal limit of ionizing radiation to which the fetus should be exposed during pregnancy is a cumulative dose of 5 rad.nIf a pregnant woman needs imaging,most single dia
24、gnostic procedures are less than 1 rad.A few single studies are between 1-5 rads.nIt is advisable to avoid exposure when possible,use ultrasound or MRI when equivalent data can be obtained.ReferencesnNational Council on Radiation Protection and Measurements.Medical radiation exposure of pregnant and
25、 potentially pregnant women.NCRP Report no.54.Bethesda,Md.:The Council,1977.nNational Council on Radiation Protection and Measurements.Considerations regarding the unintended radiation exposure of the embryo,fetus or nursing child.NCRP Commentary no 9.Bethesda,Md.:The Council,1994.nAmerican College
26、of Obstetricians and Gynecologists,Committee on Obstetric Practice.Guidelines for diagnostic imaging during pregnancy.ACOG Committee opinion no.158.Washington,D.C.:ACOG,1995nToppenberg KS,Hill A,Miller DP.Safety of Radiographic Imaging During Pregnancy.American Family Physician.April 1999nEl-Khoury
27、GY,Madsen MT,Blake ME,Yankowitz J.A New Pregnancy Policy for a New Era.AJR.Feb 2003nMiller,JC.Risks from Ionizing Radiation in Pregnancy.Radiology Rounds:A Newslette for Referring Physicians MGH Dept.of Radiology.Feb 2004.nWagner LK,Lester RG,Saldana LR.Exposure of the Pregnant Patient to Diagnostic Radiations:A guide to medical management(2nd edition).Medical Physics Publishing.1997.
