Table 2.
Demographic, health and lifestyle characteristics of primiparous women giving birth 1986–2002.
| Mode of conception | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Characteristic | Night shift workers (N = 11,000) | Day workers (N = 84,991) | Night shift vs. day workers | Not in paid employment (N = 32,861) | Fertility treatment conceptions (N = 2,058) | Natural conceptions (N = 126,794) | Treatment vs. Natural | |||||
| N | % | N | % | P-value | N | % | N | % | N | % | P-value | |
| AGE (YEARS) | ||||||||||||
| <30 | 7,139 | 64.9 | 60,185 | 70.8 | <0.001 | 28,717 | 87.4 | 579 | 28.1 | 95,462 | 75.3 | <0.001 |
| 30–34 | 2,951 | 26.8 | 19,057 | 22.4 | 3,059 | 9.3 | 909 | 44.2 | 24,158 | 19.1 | ||
| 35–39 | 797 | 7.3 | 5,027 | 5.9 | 913 | 2.8 | 474 | 23.0 | 6,263 | 4.9 | ||
| ≥40 | 113 | 1.0 | 720 | 0.8 | 169 | 0.5 | 96 | 4.7 | 906 | 0.7 | ||
| ETHNICITY | ||||||||||||
| Caucasian | 10,716 | 97.4 | 81,581 | 96.0 | <0.001 | 28,369 | 86.3 | 1,978 | 96.1 | 118,688 | 93.6 | <0.001 |
| Non-Caucasian | 284 | 2.6 | 3,410 | 4.0 | 4,492 | 13.7 | 80 | 3.9 | 8,106 | 6.4 | ||
| SOCIOECONOMIC STATUS | ||||||||||||
| Q1 (lowest quartile) | 1,708 | 15.5 | 17,114 | 20.1 | <0.001 | 11,069 | 33.7 | 350 | 17.0 | 29,541 | 23.3 | <0.001 |
| Q2 | 2,386 | 21.7 | 21,010 | 24.7 | 9,112 | 27.7 | 428 | 20.8 | 32,080 | 25.3 | ||
| Q3 | 3,012 | 27.4 | 21,165 | 24.9 | 7,941 | 24.2 | 493 | 24.0 | 31,625 | 24.9 | ||
| Q4 (highest quartile) | 3,851 | 35.0 | 25,497 | 30.0 | 4,625 | 14.1 | 784 | 38.1 | 33,189 | 26.2 | ||
| Missing | 43 | 0.4 | 205 | 0.2 | 114 | 0.3 | 3 | 0.2 | 359 | 0.3 | ||
| SMOKINGa | ||||||||||||
| Non-smoker | 3,561 | 79.8 | 28,906 | 76.0 | <0.001 | 8,431 | 56.3 | 1,512 | 82.3 | 39,386 | 70.8 | <0.001 |
| Smoker | 877 | 19.6 | 8,855 | 23.3 | 6,158 | 41.1 | 324 | 17.6 | 15,556 | 28.0 | ||
| Unknown | 26 | 0.6 | 283 | 0.7 | 378 | 2.5 | 1 | 0.1 | 686 | 1.2 | ||
| PRE-EXISTING MEDICAL CONDITIONS | ||||||||||||
| Hypertension | 140 | 1.3 | 925 | 1.1 | 0.08 | 327 | 1.0 | 28 | 1.4 | 1,364 | 1.1 | 0.2 |
| Diabetes | 27 | 0.3 | 210 | 0.2 | 0.97 | 103 | 0.3 | 6 | 0.3 | 334 | 0.3 | 0.8 |
| Asthma | 541 | 4.9 | 3,881 | 4.6 | 0.1 | 2,134 | 6.5 | 82 | 4.0 | 6,474 | 5.1 | 0.02 |
a
Routine reporting of maternal smoking on the perinatal record form did not begin until 1998. Therefore, smoking data are unavailable for 71,377 pregnancies occurring before this date.