Table 1.
Study population characteristics by type of hormonal contraceptive used 12 months before conception
| Characteristic | Study population n=44,734 % |
No hormonal contraceptive n=23,727 % |
Combination oral contraceptive n=14,012 % |
Progestin only oral contraceptive n=4,572 % |
Vaginal ring n=1,215 % |
Transdermal n=832 % |
Otherb n=376 % |
|
|---|---|---|---|---|---|---|---|---|
| Maternal age (yrs) | ||||||||
| 14-19 | 0.9 | 0.5 | 1.8 | 0.3 | 0.6 | 1.2 | 0.0 | |
| 20-29 | 42.1 | 33.1 | 56.5 | 37.7 | 54.3 | 59.0 | 47.9 | |
| 30-39 | 54.9 | 63.1 | 41.3 | 60.6 | 44.0 | 39.4 | 49.7 | |
| 40-49 | 2.1 | 3.3 | 0.4 | 1.4 | 1.1 | 0.5 | 2.4 | |
| Maternal BMI (kg/m2) | ||||||||
| <18.5 | 3.2 | 3.3 | 3.1 | 3.3 | 2.8 | 4.1 | 2.9 | |
| 18.5-24.9 | 66.0 | 65.6 | 66.8 | 65.7 | 68.8 | 65.0 | 60.1 | |
| 25.0-29.9 | 21.7 | 21.3 | 21.9 | 22.8 | 22.6 | 21.3 | 28.2 | |
| ≥30.0 | 9.0 | 9.8 | 8.2 | 8.3 | 5.8 | 9.6 | 8.8 | |
| Parity | ||||||||
| 0 | 47.1 | 37.8 | 70.6 | 17.2 | 67.4 | 57.2 | 29.5 | |
| 1 | 35.5 | 39.6 | 20.9 | 63.9 | 21.0 | 27.5 | 41.2 | |
| 2 | 13.7 | 17.6 | 7.0 | 15.0 | 9.3 | 12.7 | 21.8 | |
| 3 | 2.8 | 3.8 | 1.1 | 3.1 | 1.7 | 1.9 | 5.3 | |
| 4 or more | 0.9 | 1.3 | 0.4 | 0.8 | 0.7 | 0.6 | 2.1 | |
| Maternal education | ||||||||
| More than 4 years of university or technical | 27.2 | 29.5 | 23.4 | 30.0 | 25.8 | 16.4 | 17.8 | |
| 4 year university degree, regional technical | 40.8 | 40.0 | 40.5 | 44.7 | 46.0 | 42.0 | 33.8 | |
| 3 years high school, junior college | 13.4 | 12.7 | 15.3 | 10.6 | 13.2 | 17.7 | 17.3 | |
| Technical high school | 11.2 | 10.3 | 12.8 | 9.5 | 10.5 | 14.7 | 16.8 | |
| 1-2 years high school | 3.9 | 3.9 | 4.3 | 2.8 | 2.1 | 4.9 | 7.5 | |
| 9-year secondary | 2.2 | 2.3 | 2.3 | 1.3 | 1.1 | 2.6 | 5.3 | |
| Other | 1.4 | 1.4 | 1.4 | 1.2 | 1.4 | 1.8 | 1.6 | |
| Maternal smoking (at 17 weeks) | ||||||||
| None | 79.3 | 80.0 | 76.8 | 85.0 | 77.8 | 75.0 | 70.5 | |
| Quit | 14.5 | 13.9 | 16.5 | 10.9 | 16.5 | 16.6 | 18.6 | |
| Daily | 1.4 | 1.3 | 1.6 | 1.2 | 1.7 | 2.2 | 2.4 | |
| Sometimes | 4.8 | 4.8 | 5.1 | 3.0 | 4.1 | 6.3 | 8.5 |
a
represents unique pregnancies conceived without infertility treatments, resulting in a singleton live birth, with a date of birth ≥12 months after NorPD registry began (January 1, 2004)
b
includes the intrauterine, injectable, emergency, and implant hormonal contraceptives