Table 3. Relative Rate of First Childbirth Among Physicians and Nonphysicians Observed From Age 15 Years.
| Exposure group | Hazard ratio (95% CI)a | P value |
|---|---|---|
| Reproductive period | ||
| Nonphysician | 1 [Reference] | NA |
| Physician | 0.62 (0.59-0.65)b | <.001 |
| 15-28 y | ||
| Nonphysician | 1 [Reference] | NA |
| Physician | 0.15 (0.14-0.18) | <.001 |
| 29-36 y | ||
| Nonphysician | 1 [Reference] | NA |
| Physician | 1.35 (1.28-1.43) | <.001 |
| ≥37 y | ||
| Nonphysician | 1 [Reference] | NA |
| Physician | 2.62 (2.00-3.43) | <.001 |
Abbreviation: NA, not applicable.
a
Analyses were performed over the entire reproductive period, and in 3 separate intervals: 15-28 years, 29-36 years, and ≥37 years. Because hazards were nonproportional, the hazard ratios presented reflect the average relative rate between physicians and nonphysicians over respective time periods.
b
Findings were similar after restricting nonphysicians to the highest income quintile: hazard ratio, 0.78; 95% CI, 0.73-0.83; P < .001.