Table 1. Characteristics of the Study Population.
| Characteristic | No. (%) | P Value | ||
|---|---|---|---|---|
| Total Population (N = 111 459) | Surgery Cohort (n = 59 483) | RAIT Cohort (n = 51 976) | ||
| Age at thyroidectomy or RAIT, mean (SD), y | 39.8 (6.7) | 39.8 (6.6) | 39.8 (6.9) | .70 |
| Pregnancies | 10 842 (9.7) | 5958 (10.0) | 4884 (9.4) | <.001 |
| Age at thyroidectomy, mean (SD), y | 31.2 (4.5) | 31.5 (4.4) | 30.7 (4.5) | <.001 |
| Age at RAIT, mean (SD), y | NA | NA | 31.2 (4.5) | NA |
| Age at conception, y | .39 | |||
| Mean (SD) | 33.3 (4.4) | 33.3 (4.3) | 33.2 (4.4) | |
| 20-29 | 2003 (18.5) | 1078 (18.1) | 925 (18.9) | .25 |
| 30-34 | 5063 (46.7) | 2801 (47.0) | 2262 (46.3) | |
| 35-39 | 2810 (25.9) | 1525 (25.6) | 1285 (26.3) | |
| ≥40 | 966 (8.9) | 554 (9.3) | 412 (8.4) | |
| Conception interval, mo | <.001 | |||
| 0-5 | 1545 (1.4) | 1187 (2.0) | 358 (0.7) | |
| 6-11 | 1860 (1.7) | 1150 (1.9) | 710 (1.4) | |
| 12-23 | 3378 (3.0) | 1559 (2.6) | 1819 (3.5) | |
| ≥24 | 4059 (3.6) | 2062 (3.5) | 1997 (3.8) | |
| Deliveries, No. (% of pregnancies) | 7445 (68.7) | 4129 (69.3) | 3316 (67.9) | .12 |
| Mother-infant pairs | 7096 | 3930 | 3166 | .59 |
| Infant status | .33 | |||
| Male, single birth | 3510 (49.5) | 1914 (48.7) | 1596 (50.4) | |
| Female, single birth | 3416 (48.1) | 1923 (48.9) | 1493 (47.2) | |
| Multiple birth | 170 (2.4) | 93 (2.4) | 77 (2.4) | |
Abbreviation: RAIT, radioactive iodine treatment.