Table 3.

Risks for childhood asthma in relation to delivery modes and birth conditions.

	Controls	Ever asthma			Early-onset asthma†			Late-onset asthma‡
	N (%)§	N §	OR	95%CI	N	OR	95%CI	N §	OR	95%CI
Modes of delivery
Vaginal	255 (66.2)	128	1.00		61	1.00		67	1.00
Scheduled CS	58(15.1)	25	1.04	(0.59, 1.83)	13	1.19	(0.49, 2.88)	12	0.97	(0.45, 2.09)
Emergent CS	72(18.7)	38	1.13	(0.70, 1.83)	16	0.76	(0.37, 1.57)	22	1.63	(0.81, 3.28)
Forceps usage during vaginal delivery
No	250(98.0)	118	1.00		59	1.00		59	1.00
Yes	5(2.0)	9	2.12	(0.57, 7.91)	2	0.41	(0.04, 3.95)	7	5.10	(0.84, 30.93)
Vacuum usage during vaginal delivery
No	243(95.3)	103	1.00		51	1.00		52	1.00
Yes	12(4.7)	24	3.68	(1.34, 10.1)*	10	2.01	(0.47, 8.63)	14	5.16	(1.29, 20.60)*
Low birth weight
No	338(90.4)	158	1.00		78	1.00		80	1.00
Yes	36(9.6)	31	1.73	(0.96, 3.1)	13	1.99	(0.77, 5.13)	18	1.76	(0.81, 3.8)
2000–2500 gm	25(6.7)	22	1.70	(0.86, 3.35)	9	1.61	(0.56, 4.62)	13	1.60	(0.72, 3.55)
< 2000 gm	11(2.9)	9	1.79	(0.66, 4.87)	4	4.18	(0.65, 26.77)	5	5.69	(0.49, 65.67)
P for trend			0.08			0.10			0.09
Preterm delivery¶
No	356(92.2)	169	1.00		80	1.00		89	1.00
Yes	30(7.8)	24	1.83	(0.98, 3.41)	11	2.47	(0.94, 6.50)	13	1.4	(0.63, 3.27)
34–36 wk	22(7.2)	16	1.74	(0.81, 3.74)	8	2.51	(0.82, 7.72)	8	1.16	(0.40, 3.36)
< 34 wk	2(0.7)	5	4.31	(0.81, 2.88)	3	4.80	(0.44, 52.14)	2	4.48	(0.39, 51.97)
P for trend			0.03			0.04			0.32

Models are adjusted for parental education, mother's age at birth of her child, parental history of asthma, parental history of atopy, and in utero maternal smoking.

*P < 0.05.

^§Number of subjects does not add up to total n because of missing data.

^†Early onset: asthma diagnosed ≦3 yr of age.

^‡Late onset: asthma diagnosed >3 yr of age.

^¶Preterm delivery was defined as children born at gestational age less than 37 weeks.