Sudden infant death syndrome: a re-examination of temporal trends

Table 2 SIDS rates, rate ratios and rate differences, by plurality and gestation, United States, 2004-05 vs. 1995–96

Plurality and gestational age (weeks)	Traditional approach				Fetuses-at-risk approach
	1995-96	2004-05	2004-05 vs 1995-96		1995-96	2004-05	2004-05 vs 1995-96
	SIDS rate (per 10,000 live births)	SIDS rate (per 10,000 live births)	Rate difference	Rate ratio (95% CI)	SIDS rate (per 10,000 FAR)	SIDS rate (per 10,000 FAR)	Rate difference	Rate ratio (95% CI)
Singletons
22-36 weeks	20.34	12.31	−8.0	0.61 (0.60-0.61)	1.52	1.08	−0.4	0.71 (0.71-0.71)
≥37 weeks	7.32	4.93	−2.4	0.67 (0.67-0.67)	6.74	4.48	−2.3	0.67 (0.67-0.67)
Total	8.30	5.58	−2.7	0.67 (0.67-0.67)	8.26	5.56	−2.7	0.67 (0.67-0.67)
Twins
22-36 weeks	17.65	12.27	−5.4	0.70 (0.69-0.70)	9.35	7.59	−1.8	0.81 (0.81-0.82)
≥37 weeks	10.34	7.96	−2.4	0.77 (0.76-0.78)	10.32	7.95	−2.3	0.77 (0.76-0.78)
Total	14.25	10.64	−3.6	0.75 (0.74-0.75)	14.12	10.58	−3.5	0.75 (0.74-0.75)

95% CI denotes 95% confidence intervals; SIDS cases were defined by the underlying cause of death 7980 (ICD-9) in 1995–06 and R95 (ICD-10) in 2004–05. The discrepancy in total SIDS rates under the traditional and fetuses-at-risk approaches is because stillbirths were included in the denominator for the latter calculation. Rate differences were calculated per 10,000 live births and 10,000 fetuses-at-risk.

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