Prenatal X-ray exposure and childhood cancer in Swedish twins.
The association between X-ray exposure in utero and childhood cancer was studied in a case-control study, nested in a national cohort of Swedish twin births. Records of the Swedish Twin Register for those born 1936-1967 (n = 83,316) were linked to the Swedish Cancer Register (1958-1983) and the Swedish Cause-of-Death Register (1952-1983). Ninety-five cases of childhood cancer before the age of 16 were identified. Two controls from the Twin Register were matched to each case by sex and year of birth. Maternal X-rays during pregnancy were documented for 41% of the cases and 36% of the controls. The crude relative risk of any childhood cancer associated with any prenatal X-ray was 1.2 (95% CI; 0.7-2.1). For the cases 64% of the X-rayed women had had abdominal X-rays, the numbers for the controls were 57%. Fifty-nine per cent of the X-rayed women had had abdominal X-rays, which were associated with a relative risk for all cancers of 1.4 (Cl; 0.8-2.5), leukemias 1.7 (Cl; 0.7-4.1) and tumors of the central nervous system 1.5 (Cl; 0.5-4.2). There was no apparent confounding by mother's age, drug use, obstetric complications, previous miscarriages, social class or length of pregnancy. The observed relative risks of cancer following prenatal X-ray exposure are consistent with previous studies, suggesting that the developing fetus may be more sensitive to the carcinogenic effects of ionizing radiation than are children irradiated post-natally.
Department of Epidemiology, Karolinska Institute, Stockholm, Sweden.
Y
Y
Rodvall
G
G
Pershagen
Z
Z
Hrubec
A
A
Ahlbom
N L
NL
Pedersen
J D
JD
Boice
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005314:Embryonic and Fetal Development / Q000528:radiation effects; D005260:Female; D006801:Humans; D008297:Male; D008423:Maternal Age; D009381:Neoplasms, Radiation-Induced / Q000453:epidemiology*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011859:Radiography / Q000009:adverse effects*; D012042:Registries; D012307:Risk Factors; D012737:Sex Factors; D013548:Sweden; D014427:Twins