Table 3

Association between estimated paternal serum TCDD concentration at time of birth and the probability of a male offspring, stratified by father's age of first exposure (estimated by father's age at start of employment)

Fathers employed at plant (n=127)
Age of father at start of employment	Girls (n)	Boys (n)	Sex ratio	Crude OR	95% CI	OR*	95% CI
23–30
<4 pg/g lipid	15	24	0.62	1.00	ref	1.00	ref
4–20 pg/g lipid	4	9	0.69	1.37	0.36 to 5.31	2.00	0.35 to 11.4
20–100 pg/g lipid	4	5	0.56	0.51	0.16 to 1.68	0.17	0.04 to 0.68
≥100 pg/g lipid	3	1	0.25	0.20	0.03 to 1.37	0.04	0.01 to 0.26
				p trend	0.128	p trend	0.016
30–37
<4 pg/g lipid	24	43	0.64	1.00	ref	1.00	ref
4–20 pg/g lipid	3	5	0.63	0.94	0.19 to 4.75	1.26	0.20 to 8.08
20–100 pg/g lipid	12	11	0.48	0.51	0.25 to 1.07	0.37	0.16 to 0.85
≥100 pg/g lipid	8	7	0.47	0.49	0.12 to 2.09	0.59	0.18 to 1.95
				p trend	0.148	p trend	0.062
>37
<4 pg/g lipid	20	21	0.51	1.00	ref	1.00	ref
4–20 pg/g lipid	8	10	0.56	1.20	0.42 to 3.48	2.02	0.78 to 5.21
20–100 pg/g lipid	14	11	0.44	0.75	0.28 to 2.05	0.87	0.34 to 2.25
≥100 pg/g lipid	22	20	0.48	0.86	0.35 to 2.12	1.22	0.48 to 3.13
				p trend	0.625	p trend	0.934

*OR (modelling the probability of a male birth) adjusted for: age of parent at year of birth, current BMI of parent, smoking status of parent.
BMI, body mass index; TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin.