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Table 5 Relative contribution of changes in the gestational age distribution and in gestational age-specific small-for-gestational age (SGA) rates to temporal changes in sga rates among singleton live births to smokers in the United States (1990–1992 vs. 2002–2004; 2002–2004 vs. 2008–2010)

From: The association between temporal changes in the use of obstetrical intervention and small- for-gestational age live births

Period Gestational Age (weeks) Modified Kitagawa decomposition (per 10,000 fetuses-at-risk)
Contribution of changes in Total change Relative contribution of changes in
Gestational age Gestational age-specific SGA   Gestational age (%) Gestational age-specific SGA (%)
1990–1992 vs. 2002–2004 24–33 weeks 0.00 5.71 5.71 −0.1 100.1
34–36 weeks −0.90 22.55 21.66 −4.1 104.1
37–38 weeks −20.04 126.93 106.89 −18.8 118.8
39–40 weeks −300.73 65.70 −235.02 128.0 −28.0
41 weeks −61.97 −0.14 −62.11 99.8 0.2
≥42 weeks −31.95 −0.20 −32.15 99.4 0.6
Total −415.59 220.57 −195.02 213.1 −113.1
2002–2004 vs. 2008–2010 24–33 weeks 0.02 1.22 1.24 1.6 98.4
34–36 weeks 0.22 −1.07 −0.86 −25.3 125.3
37–38 weeks 0.25 41.99 42.25 0.6 99.4
39–40 weeks −77.13 77.82 0.68 −11290.7 11390.7
41 weeks −20.00 1.46 −18.54 107.9 −7.9
≥42 weeks −4.01 0.12 −3.89 103.2 −3.2
Total −100.67 121.54 20.88 −482.2 582.2