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Trend test in spontaneous preterm birth incidence rates in multiparous women
| P1 | P2 | P3 | P4 | P-value* | |
|---|---|---|---|---|---|
| Spontaneous PTB | |||||
| < 37 weeks | 8065 (2.8%) | 2761 (2.6%) | 893 (2.9%) | 347 (3.7%) | 0.0178 |
| < 32 weeks | 873 (0.3%) | 349 (0.3%) | 121 (0.4%) | 58 (0.6%) | <.0001 |
| < 28 weeks | 367 (0.1%) | 142 (0.1%) | 64 (0.2%) | 37 (0.4%) | <.0001 |
| 34–37 weeks | 6406 (2.2%) | 2118 2.0%) | 675 (2.2%) | 251 (2.7%) | NS |
Abbreviations: PTB preterm birth
* Two-sided Cochran-Armitage Trend Test
