Table 2. Perinatal characteristics, including birth weight and the risk of childhood RMS, and its two major subtypes (embryonal RMS and alveolar RMS).

	All RMS		Embryonal RMS		Alveolar RMS
Variable	ORa (N)	95% CI	ORa (N)	95% CI	ORa (N)	95% CI
Maternal race
White	Ref (494)		Ref (312)		Ref (69)
Black	0.93 (43)	0.67–1.29	0.76 (22)	0.48–1.21	1.43 (9)	0.70–2.92
Asian	1.01 (26)	0.66–1.54	1.02 (18)	0.61–1.71	(3)
Other	1.44 (14)	0.83–2.51	2.04 (11)	1.09–3.84	(2)
Maternal age (years)
<20	0.84 (65)	0.62–1.15	0.70 (35)	0.46–1.05	1.08 (11)	0.50–2.33
20–24	0.81 (131)	0.64–1.02	0.78 (79)	0.58–1.05	0.91 (21)	0.51–1.64
25–29	Ref (188)		Ref (118)		Ref (28)
30–34	1.06 (131)	0.84–1.33	1.05 (83)	0.78–1.41	0.77 (15)	0.40–1.48
⩾35	1.35 (68)	1.01–1.81	1.54 (48)	1.08–2.19	1.27 (10)	0.60–2.69
Per 1-year increase	1.03	1.01–1.04	1.04	1.02–1.06	1.01	0.97–1.05
Paternal ageb (years)
<20	0.84 (17)	0.49–1.44	0.50 (7)	0.22–1.15	2.57 (5)	0.83–7.98
20–24	0.75(74)	0.56–1.00	0.72 (46)	0.50–1.04	1.26 (11)	0.58–2.76
25–29	Ref (158)		Ref (102)		Ref (17)
30–34	1.04 (139)	0.82–1.32	1.01 (86)	0.75–1.36	1.70 (23)	0.88–3.27
⩾35	1.21 (119)	0.94–1.56	1.24 (77)	0.90–1.69	1.82 (18)	0.90–3.68
Per 1-year increase	1.02	1.01–1.03	1.02	1.00–1.04	1.02	0.98–1.06
Child's sex
Male	1.27 (348)	1.07–1.51	1.29 (221)	1.04–1.60	1.19 (47)	0.77–1.85
Female	Ref (235)		Ref (142)		Ref (38)
Gestational age
⩽36 weeks	1.02 (42)	0.71–1.45	1.02 (26)	0.65–1.60	0.92 (7)	0.42–2.04
37–40 weeks	Ref (349)		Ref (218)		Ref (52)
>40 weeks	0.98 (173)	0.81–1.18	0.94 (105)	0.74–1.19	0.93 (24)	0.56–1.53
Plurality
Single birth	Ref (570)		Ref (356)		(82)
Multiple birth	1.32 (13)	0.74–2.36	1.13 (7)	0.52–2.48	(3)
Birth order
First	Ref (261)		Ref (170)		Ref (34)
Second	0.82 (178)	0.67–1.00	0.72 (105)	0.55–0.92	1.01 (25)	0.59–1.74
Third	0.70 (82)	0.54–0.91	0.57 (48)	0.40–0.80	1.23 (15)	0.64–2.34
Fourth +	0.75 (59)	0.55–1.02	0.69 (38)	0.47–1.01	1.12 (11)	0.51–2.48
Birth weight
<2000 g	0.52 (7)	0.22–1.24	0.59 (4)	0.20–1.71	(1)
2000–2499 g	0.66 (15)	0.38–1.14	0.67 (9)	0.33–1.35	(1)
2500–3999 g	Ref (476)		Ref (294)		Refc (75)
4000–4499 g	1.08 (64)	0.82–1.42	1.21 (44)	0.87–1.69	0.48 (5)	0.19–1.19
⩾4500 g	1.21 (15)	0.70–2.08	1.55 (11)	0.84–2.86	(2)
Per 500 g increase	1.18	1.09–1.29	1.27	1.14–1.42	0.92	0.74–1.14

Abbreviations: CI=confidence interval; OR=odds ratio; RMS=rhabdomyosarcoma.

^aAdjusted for birth year, state, maternal age, maternal race, child's sex, plurality and birth order.

^bAdjusted for birth year, state, maternal race, child's sex, plurality, gestational age, birth weight and birth order.

^cBirth weight <4000 g was used as a reference and compared with birth weight ⩾4000 g. Terms given in bold mark statistically significant results.