Table 3 Relative contribution of changes in the gestational age distribution and in gestational age-specific small-for-gestational age (SGA) rates to the overall temporal changes in sga rates among singleton live births in the United States (1990–1992 vs. 2002–2004; 2002–2004 vs. 2008–2010)
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 | Â | Gestational age (%) | Gestational age-specific SGA (%) | ||
1990–1992 vs. 2002–2004 | 24–33 weeks | 0.00 | 4.58 | 4.58 | 0.0 | 100.0 |
34–36 weeks | −0.37 | 9.71 | 9.34 | −4.0 | 104.0 | |
37–38 weeks | −8.83 | 55.44 | 46.61 | −18.9 | 118.9 | |
39–40 weeks | −168.20 | 33.63 | −134.57 | 125.0 | −25.0 | |
41 weeks | −34.71 | 1.98 | −32.73 | 106.0 | −6.0 | |
≥42 weeks | −16.53 | −0.48 | −17.01 | 97.2 | 2.8 | |
Total | −228.65 | 104.87 | −123.78 | 184.7 | −84.7 | |
2002–2004 vs. 2008-2010 | 24–33 weeks | 0.01 | −0.31 | −0.30 | −3.3 | 103.3 |
34–36 weeks | 0.12 | −0.26 | −0.14 | −85.7 | 185.7 | |
37–38 weeks | 0.48 | 24.75 | 25.23 | 1.9 | 98.1 | |
39–40 weeks | −38.16 | 45.14 | 6.99 | −546.2 | 646.2 | |
41 weeks | −9.58 | 0.95 | −8.63 | 111.0 | −11.0 | |
≥42 weeks | −1.84 | 0.09 | −1.74 | 105.3 | −5.3 | |
Total | −48.96 | 70.36 | 21.41 | −228.7 | 328.6 | |