Table 2 Small-for-gestational age (SGA) rates, rate ratios and rate differences by gestational age among singleton live births in the United States (1990–1992 vs. 2002–2004; 2002–2004 vs. 2008–2010)
Gestational Age (weeks) | Fetuses-at-Risk (FAR) Approach | |||
|---|---|---|---|---|
1990–1992 | 2002–2004 | 2002–2004 vs. 1990–1992 | ||
SGA per 100 FAR | SGA per 100 FAR | Rate Difference | Rate Ratio (95Â % CI) | |
24–33 weeks | 0.21 | 0.25 | +0.05 | 1.22 (1.20–1.25) |
34–36 weeks | 0.82 | 0.92 | +0.10 | 1.12 (1.11–1.13) |
37–38 weeks | 2.30 | 2.84 | +0.54 | 1.24 (1.23–1.24) |
39–40 weeks | 7.99 | 7.27 | −0.72 | 0.91 (0.91–0.91) |
41 weeks | 4.72 | 4.88 | +0.16 | 1.03 (1.02–1.05) |
≥42 weeks | 5.21 | 4.88 | −0.33 | 0.94 (0.91–0.97) |
Total | 10.1 | 8.89 | −1.23 | 0.88 (0.88–0.88) |
á…Ÿ | á…Ÿ | á…Ÿ | á…Ÿ | á…Ÿ |
|  | 2002–2004 | 2008–2010 | 2008–2010 vs. 2002–2004 | |
| Â | SGA per 100 FAR | SGA per 100 FAR | Rate Difference | Rate Ratio (95Â % CI) |
24–33 weeks | 0.25 | 0.25 | 0.0 | 0.99 (0.97–1.00) |
34–36 weeks | 0.92 | 0.91 | −0.01 | 1.00 (0.99–1.01) |
37–38 weeks | 2.84 | 3.10 | +0.26 | 1.09 (1.09–1.10) |
39–40 weeks | 7.27 | 7.44 | +0.17 | 1.02 (1.02–1.03) |
41 weeks | 4.88 | 5.00 | +0.12 | 1.02 (1.01–1.04) |
≥42 weeks | 4.88 | 5.20 | +0.32 | 1.07 (1.01–1.12) |
Total | 8.89 | 9.11 | +0.21 | 1.02 (1.02–1.03) |