Table 3.
Annual household income and fecundability, overall and stratified by age at baseline, cycles of pregnancy attempt time at study entry, and nationality (n=8,654)
| No. of cycles | No. of Pregnancies | Unadjusted FR (95% CI) | Adjusted FR (95% CI)a | Adjusted FR (95% CI)b | |
|---|---|---|---|---|---|
| Income (USD) | |||||
| <50,000 | 6,529 | 840 | 0.88 (0.80–0.96) | 0.91 (0.83–1.01) | 0.95 (0.86–1.06) |
| 50,000–99,000 | 13,068 | 1,970 | 0.97 (0.90–1.05) | 0.99 (0.92–1.07) | 1.01 (0.93–1.09) |
| 100,000–149,000 | 8,148 | 1,432 | 1.09 (1.01–1.18) | 1.09 (1.01–1.18) | 1.10 (1.02–1.19) |
| ≥150,000 | 5,342 | 861 | Reference | Reference | Reference |
| Age <30 years (n=4,251) | |||||
| <50,000 | 4,182 | 596 | 0.93 (0.81–1.07) | 1.10 (0.95–1.28) | 1.12 (0.96–1.31) |
| 50,000–99,000 | 6,727 | 1,095 | 1.01 (0.89–1.16) | 1.12 (0.98–1.29) | 1.12 (0.98–1.29) |
| 100,000–149,000 | 3,232 | 616 | 1.16 (1.01–1.33) | 1.20 (1.05–1.38) | 1.20 (1.04–1.38) |
| ≥150,000 | 1,390 | 230 | Reference | Reference | Reference |
| Age ≥30 years (n=4,403) | |||||
| <50,000 | 2,347 | 244 | 0.76 (0.65–0.88) | 0.88 (0.76–1.03) | 0.86 (0.73–1.01) |
| 50,000–99,000 | 6,341 | 875 | 0.92 (0.84–1.01) | 0.98 (0.89–1.09) | 0.96 (0.86–1.06) |
| 100,000–149,000 | 4,916 | 816 | 1.04 (0.95–1.15) | 1.05 (0.95–1.16) | 1.05 (0.95–1.16) |
| ≥150,000 | 3,952 | 631 | Reference | Reference | Reference |
| <3 cycles (n=5,689) | |||||
| <50,000 | 3,779 | 525 | 0.86 (0.77–0.96) | 0.91 (0.81–1.02) | 0.95 (0.84–1.08) |
| 50,000–99,000 | 8,962 | 1,438 | 0.99 (0.90–1.08) | 1.01 (0.92–1.11) | 1.03 (0.93–1.13) |
| 100,000–149,000 | 5,585 | 1,084 | 1.13 (1.04–1.24) | 1.13 (1.03–1.24) | 1.14 (1.05–1.25) |
| ≥150,000 | 3,917 | 652 | Reference | Reference | Reference |
| US women (n=7,247) | |||||
| <50,000 | 5,643 | 718 | 0.88 (0.79–0.97) | 0.96 (0.86–1.07) | 0.96 (0.85–1.08) |
| 50,000–99,000 | 10,814 | 1,597 | 0.97 (0.89–1.05) | 1.02 (0.93–1.11) | 1.01 (0.92–1.10) |
| 100,000–149,000 | 6,712 | 1,144 | 1.07 (0.99–1.16) | 1.08 (0.99–1.17) | 1.08 (0.99–1.18) |
| ≥150,000 | 4,678 | 753 | Reference | Reference | Reference |
FR=fecundability ratio, CI=confidence interval, USD=United States dollar.
a
Model 1 adjusted for age, education, male partner education, and race/ethnicity.
b
Model 2 adjusted for variables in model A and marital status, BMI, smoking, physical activity, cycle length, intercourse frequency, last method of contraception, history of sexually transmitted infection, doing something to improve chances of pregnancy, PSS score, MDI score, sleep duration, employment status, hours worked per week, and Healthy Eating Index score.