Factors associated with birthweight decline in Japan (1980–2004)

Table 4 Multivariate analysis with sequential adjustment, according to several time periods

All births	1980–1984 (early period)			1985–1989			1990–1994
Yearly effect	Birth weight (g)	Standard error	r²	Birth weight (g)	Standard error	r²	Birth weight (g)	Standard error	r²
Crude	−3.98	0.11	0.0002	−8.50	0.12	0.0007	−8.71	0.13	0.0008
Adjusted for gestational age	−0.07	0.10	0.2151	−3.60	0.10	0.2483	−7.58	0.11	0.2843
Plus neonatal gender	0.02	0.10	0.2289	−3.53	0.10	0.2628	−7.57	0.10	0.2991
Plus delivery number	−0.19	0.10	0.2441	−3.42	0.10	0.2805	−6.32	0.10	0.3184
Plus multiple gestation	−0.32	0.10	0.2607	−3.42	0.10	0.2948	−5.97	0.10	0.3326
Plus live birth number	−0.33	0.10	0.2607	−3.47	0.10	0.2948	−5.97	0.10	0.3226
Plus father age	−0.53	0.10	0.2592	−3.66	0.10	0.2936	−5.99	0.10	0.3316
All births	1995–1999			2000–2004 (late period)			1980–2004 (total period)
Yearly effect	Birth weight (g)	Standard error	r²	Birth weight (g)	Standard error	r²	Birth weight (g)	Standard error	r²
Crude	−7.66	0.13	0.0006	−4.84	0.13	0.0002	−8.07	0.01	0.0175
Adjusted for gestational age	−7.01	0.10	0.3150	−3.04	0.10	0.3456	−5.63	0.01	0.2872
Plus neonatal gender	−7.02	0.10	0.3302	−2.99	0.10	0.3607	−5.60	0.01	0.3015
Plus delivery number	−6.42	0.10	0.3480	−2.96	0.10	0.3754	−5.16	0.01	0.3180
Plus multiple gestation	−6.28	0.10	0.3621	−2.79	0.10	0.3884	−5.06	0.01	0.3327
Plus live birth number	−6.28	0.10	0.3621	− 2.79	0.10	0.3884	−5.07	0.01	0.3327
Plus father age	−6.26	0.10	0.3613	−2.87	0.10	0.3872	−5.13	0.01	0.3315

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