Table 4 Small-for-gestational age (SGA) rates, rate ratios and rate differences by gestational age among singleton live births to smokers 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 | 0.3 | 0.3 | +0.06 | 1.20 (1.15–1.26) |
34–36 weeks | 1.4 | 1.6 | +0.22 | 1.16 (1.14–1.18) |
37–38 weeks | 4.2 | 5.5 | +1.28 | 1.30 (1.29–1.32) |
39–40 weeks | 14.3 | 13.2 | −1.14 | 0.92 (0.91–0.93) |
41 weeks | 9.0 | 9.0 | −0.01 | 1.00 (0.97–1.02) |
≥42 weeks | 9.9 | 9.5 | −0.38 | 0.96 (0.90–1.03) |
Total | 17.6 | 15.7 | −1.95 | 0.89 (0.88–0.89) |
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 | 0.3 | 0.4 | +0.01 | 1.04 (0.99–1.09) |
34–36 weeks | 1.6 | 1.6 | −0.01 | 0.99 (0.97–1.02) |
37–38 weeks | 5.5 | 6.0 | +0.45 | 1.08 (1.07–1.10) |
39–40 weeks | 13.2 | 13.4 | +0.20 | 1.02 (1.01–1.03) |
41 weeks | 9.0 | 9.2 | +0.20 | 1.02 (0.99–1.06) |
≥42 weeks | 9.5 | 10.0 | +0.55 | 1.06 (0.94–1.18) |
Total | 15.7 | 15.9 | +0.21 | 1.01 (1.01–1.02) |