TABLE 2.
Adjusteda pregnancy loss risks, differences, relative risks, and 95% confidence intervals (CI) for early ultrasound characteristics: joint categorization by small crown–rump length and low fetal heart rate
| Small crown–rump length | Low fetal heart rate | Risk (95% CI) | Difference (95% CI) | Relative risk (95% CI) |
|---|---|---|---|---|
| No | No | 5.0% (1.5–8.5%) | Reference | Reference |
| No | Yes | 12% (2.1–22%) | 7.0% (−3.3% to 17%) | 1.33 (0.12–2.53) |
| Yes | No | 15% (8.3–23%) | 10% (2.5–18%)b | 1.79 (0.86–2.71) |
| Yes | Yes | 21% (15–27%) | 16% (9.1–23%)b | 2.08 (1.24–2.91)b |
Risk differences may not calculate exactly from risk column because of rounding percentages to the nearest whole number.
a
Gestational age (in weeks) at ultrasound since last menstrual period (continuous);
b
Values are significantly different from reference category.