Table 4 Associations of birth weight and gestational age with lung function in z-scores at ~17.5 years in Hong Kong’s “Children of 1997” birth cohort (After inverse probability weighting and multiple imputation).

From: Birth weight and prematurity with lung function at ~17.5 years: “Children of 1997” birth cohort

Sex	Exposures	FEV₁, z-score				FVC, z-score				FEV₁/FVC, z-score				FEF_25–75%, z-scores
		Crude		Model 1^a		Crude		Model 1^a		Crude		Model 1^a		Crude		Model 1^a
		β	95%CI	β	95%CI	β	95%CI	β	95%CI	β	95%CI	β	95%CI	β	95%CI	β	95%CI
Both	Gestational age, w	0.01	−0.02 to 0.03	0.01	−0.02 to 0.03	0.00	−0.02 to 0.03	0.00	−0.02 to 0.03	0.01	−0.02 to 0.04	0.02	−0.01 to 0.05	0.02*	0.00 to 0.05	0.02*	0.00 to 0.05
	Preterm
	Full term birth	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—
	Preterm birth	−0.07	−0.25 to 0.12	−0.07	−0.26 to 0.11	0.08	−0.10 to 0.26	0.07	−0.10 to 0.25	−0.26*	−0.48 to 0.04	−0.26*	−0.48 to −0.04	−0.26*	−0.46 to 0.05	−0.26*	−0.46 to −0.06
	Birth weight, kg ^b	0.20*	0.11 to 0.29	0.26*	0.15 to 0.37	0.12*	0.03 to 0.21	0.18*	0.07 to 0.28	0.19*	0.08 to 0.30	0.22	−0.09 to 0.36	0.26*	0.16 to 0.37	0.31*	0.19 to 0.43
	Birth weight z-score ^c	0.07*	0.03 to 0.12	0.07*	0.03 to 0.12	0.07*	0.03 to 0.11	0.07*	0.03 to 0.11	0.03	0.02 to 0.08	0.03	−0.02 to 0.08	0.07*	0.03 to 0.12	0.07*	0.02 to 0.12
	Size for gestational age
	AGA	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—
	LGA	0.12	−0.02 to 0.25	0.12	−0.02 to 0.26	0.13*	0.00 to 0.27	0.14*	0.00 to 0.27	0.04	−0.13 to 0.20	0.04	−0.13 to 0.20	0.15*	0.00 to 0.30	0.15*	0.00 to 0.30
	SGA^#	−0.19*	−0.34 to −0.05	−0.19*	−0.34 to −0.04	−0.14	−0.29 to 0.01	−0.13	−0.28 to −0.01	−0.11	−0.29 to 0.07	0.10	−0.28 to 0.08	−0.20*	−0.36 to −0.03	−0.19*	−0.36 to −0.02
Girls	Gestational age, w	0.03	−0.01 to 0.07	0.03*	0.00 to 0.07	0.01	−0.03 to 0.04	0.01	−0.03 to 0.04	0.05*	0.01 to 0.10	0.06*	0.02 to 0.11	0.06*	0.02 to 0.10	0.07*	0.02 to 0.11
	Preterm
	Full term birth	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—
	Preterm birth	−0.21	−0.51 to 0.08	−0.23	−0.53 to 0.06	0.05	−0.22 to 0.33	0.03	−0.25 to 0.31	−0.48*	−0.82 to −0.14	−0.47*	−0.82 to −0.12	−0.31*	−0.53 to −0.09	−0.31*	−0.53 to −0.09
	Birth weight, kg ^b	0.17*	0.03 to 0.31	0.17*	0.03 to 0.31	0.11	−0.02 to 0.25	0.11	−0.02 to 0.25	0.14	−0.02 to 0.31	0.14	−0.02 to 0.31	0.25*	0.10 to 0.41	0.25*	0.10 to 0.41
	Birth weight z-score ^c	0.06*	0.00 to 0.12	0.06*	0.00 to 0.12	0.06*	0.00 to 0.12	0.06*	0.00 to 0.12	0.02	−0.05 to 0.09	0.02	−0.06 to 0.09	0.07*	0.01 to 0.14	0.07*	0.00 to 0.14
	Size for gestational age
	AGA	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—
	LGA	0.12	−0.08 to 0.31	0.11	0.09 to 0.31	0.19*	0.00 to 0.38	0.18	−0.01 to 0.37	−0.04	−0.27 to 0.19	−0.05	−0.28 to 0.19	0.12	−0.02 to 0.34	0.12	−0.10 to 0.34
	SGA^#	−0.14	−0.35 to 0.06	−0.12	−0.33 to 0.09	−0.07	−0.27 to 0.13	−0.06	−0.25 to 0.14	−0.12	−0.36 to 0.13	−0.10	−0.35 to 0.14	−0.22	−0.44 to 0.01	−0.20	−0.43 to 0.03
Boys	Gestational age, w	0.00	−0.03 to 0.04	0.00	−0.03 to 0.03	0.00	−0.03 to 0.03	0.00	−0.04 to 0.03	0.01	−0.03 to 0.05	0.01	−0.03 to 0.05	0.02	−0.02 to 0.05	0.01	−0.02 to 0.05
	Preterm
	Full term birth	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—
	Preterm birth	−0.03	−0.25 to 0.20	−0.03	−0.26 to 0.20	0.10	−0.14 to 0.33	0.09	−0.15 to 0.32	−0.23	−0.50 to 0.04	−0.22	−0.50 to 0.05	−0.23*	−0.49 to 0.02	−0.24*	−0.49 to −0.02
	Birth weight, kg ^b	0.16*	0.04 to 0.28	0.22*	0.07 to 0.36	0.13*	0.01 to 0.26	0.20*	0.05 to 0.35	0.08	−0.06 to 0.22	0.09	−0.08 to 0.27	0.17*	0.04 to 0.30	0.20*	0.03 to 0.36
	Birth weight z-score ^c	0.08*	0.03 to 0.14	0.08*	0.02 to 0.13	0.08*	0.02 to 0.14	0.07*	0.02 to 0.13	0.03	−0.03 to 0.10	0.03	−0.04 to 0.10	0.07*	0.01 to 0.13	0.06*	0.00 to 0.12
	Size for gestational age
	AGA	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—	Ref	—
	LGA	0.12	−0.06 to 0.30	0.10	−0.08 to 0.29	0.08	−0.11 to 0.27	0.08	−0.11 to 0.27	0.11	−0.10 to 0.33	0.10	−0.12 to 0.32	0.18	−0.03 to 0.38	0.16	−0.04 to 0.36
	SGA	−0.21*	−0.41 to −0.01	−0.20*	−0.40 to 0.00	−0.21	−0.43 to −0.01	−0.20	−0.42 to 0.02	−0.03	−0.27 to 0.22	−0.02	−0.27 to 0.22	−0.12	−0.35 to 0.11	−0.11	−0.34 to −0.12

Abbreviations: SGA, small-for-gestational age; AGA, appropriate-for-gestational age; LGA, large-for-gestational age; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; FEF_25–75%, forced expiratory flow at 25–75% of the pulmonary volume.
^aAdjusted for birth order, maternal age at birth, maternal smoking, maternal birthplace, and parental social-economic positions (SEP, including household income, the highest parental occupation at recruitment and the highest parental occupation).
^bApart from the adjustment in footnote a, adjusted for gestational age.

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Table 4 Associations of birth weight and gestational age with lung function in z-scores at ~17.5 years in Hong Kong’s “Children of 1997” birth cohort (After inverse probability weighting and multiple imputation).

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