Table 1.
Evolution for the study period of several population variables.
| Year | ||||||
| Variable |
1998 (n = 315) |
1999 (n = 316) |
2000 (n = 302) |
2001 (n = 306) |
2002 (n = 320) |
P-value |
| Age in years, mean ± SD | 28.6 ± 5.0 | 29.6 ± 5.3 | 29.9 ± 4.9 | 29.9 ± 4.5 | 30.1 ± 4.9 | < 0.001a |
| Primiparous, n (%) | 135 (42.9) | 137 (43.4) | 140 (46.4) | 130 (42.5) | 141 (44.1) | 0.603b |
| Education higher than secondary school, n (%) | 181 (57.5) | 155 (49.1) | 121 (40.1) | 121 (39.5) | 180 (56.2) | < 0.001b |
| Married, n (%) | 279 (88.6) | 292 (92.4) | 274 (90.7) | 278 (90.8) | 295 (92.2) | 0.367b |
| Employment out home, n (%) | 161 (51.1) | 173 (54.7) | 144 (47.7) | 146 (47.7) | 149 (46.6) | 0.164b |
| Social class I-II, n (%) | 41 (13.0) | 37 (11.7) | 49 (16.2) | 37 (12.1) | 36 (11.2) | 0.227b |
| Kessner index: adequate prenatal care, n (%) | 122 (38.7) | 99 (31.3) | 95 (31.5) | 128 (41.8) | 159 (49.7) | < 0.001b |
| Smokers prior to pregnancy, n (%) | 169 (53.6) | 163 (51.6) | 132 (43.7) | 135 (44.1) | 126 (39.4) | < 0.001b |
| No. cig/d, mean ± SD | 14.5 ± 7.6 | 14.9 ± 8.7 | 15.9 ± 8.6 | 17.1± 11.1 | 16.0 ± 8.9 | 0.207a |
| Smoking during the whole pregnancy, n (%) | 106 (33.7) | 115 (36.4) | 108 (35.8) | 104 (34.0) | 100 (31.2) | 0.367b |
a One-way analysis of variance
b Mantel-Haenszel trend test