Table 3. Cox proportional hazards regression modelling of the association between in utero IR exposure and childhood cancer in the offspring of female RTs (n=81 262).

Cancer type	Person-years	Cases	HRa	95% CI	P-trend
Leukaemia
0 mGy	637 994	28	1.0	ref.
>0–0.17 mGy	369 381	17	1.1	0.6–2.0
0.18–1.0 mGy	381 244	15	0.9	0.5–1.8
1.01–12.6 mGy	56 252	3	1.1	0.3–3.7	0.72
Lymphoma
0 mGy	637 994	14	1.0	ref.
>0–0.17 mGy	369 381	16	2.3	1.1–4.9
0.18–1.0 mGy	381 244	14	1.8	0.9–3.9
1.01–12.6 mGy	56 252	4	2.7	0.9–8.7	0.32
Solid tumours
0 mGy	637 994	51	1.0	ref.
>0–0.17 mGy	369 381	30	1.0	0.6–1.6
0.18–1.0 mGy	381 244	29	0.9	0.6–1.5
1.01–12.6 mGy	56 252	5	1.2	0.5–3.1	0.44
Childhood cancers overall
0 mGy	637 994	93	1.0	ref.
>0–0.17 mGy	369 381	63	1.2	0.9–1.7
0.18–1.0 mGy	381 244	58	1.1	0.8–1.5
1.01–12.6 mGy	56 252	12	1.4	0.8–2.6	0.41

CI=confidence interval; HR=hazard ratio; IR=ionising radiation; RT=radiologic technologist.

^aAdjusted for birth year.