Table 1.
Maternal and infant characteristics of singleton live births in Portugal, 1995–2014
| Variable | 1995–1999 n (%) |
2000–2006 n (%) |
2007–2014 n (%) |
Effect size (Cohen's d)* |
|---|---|---|---|---|
| Total live births | 546 032 (26.7) | 762 325 (37.3) | 736 798 (36.0) | |
| Maternal nationality | ||||
| Portugal | 530 430 (97.1) | 709 199 (93.0) | 663 963 (90.1) | 0.11 |
| Other country | 15 602 (2.9) | 53 126 (7.0) | 72 835 (9.9) | |
| Paternal age, mean (±) years | 30.4 (6.14) | 31.5 (6.24) | 32.6 (6.33) | |
| Maternal age (years) | ||||
| Mean (±) | 27.6 (5.49) | 28.7 (5.57) | 30.1 (5.63) | |
| ≤19 | 37 710 (6.9) | 42 906 (5.6) | 29 734 (4.0) | 0.13 |
| 20–34 | 447 384 (81.9) | 605 099 (79.4) | 541 738 (73.5) | |
| ≥35 | 60 938 (11.2) | 114 320 (15.5) | 165 326 (22.4) | |
| Parity | ||||
| Primiparae | 292 274 (53.5) | 415 066 (54.5) | 399 175 (54.3) | 0.01 |
| Multiparae | 253 756 (46.5) | 347 038 (45.5) | 336 564 (45.7) | |
| Maternal education | ||||
| Primary | 375 555 (68.8) | 420 124 (55.1) | 284 270 (39.2) | 0.24 |
| Secondary | 99 277 (18.2) | 179 741 (23.6) | 209 131 (28.8) | |
| Tertiary | 71 200 (13.0) | 162 220 (21.3) | 232 626 (32.0) | |
| Maternal employment status | ||||
| Employed | 342 306 (62.7) | 544 958 (71.5) | 511 140 (70.8) | 0.18 |
| Unemployed | 24 088 (4.4) | 47 093 (6.2) | 93 950 (13.0) | |
| Others | 179 638 (32.9) | 169 635 (22.3) | 116 416 (16.1) | |
| Paternal employment status | ||||
| Employed | 509 082 (96.5) | 707 149 (94.8) | 634 764 (89.2) | 0.13 |
| Unemployed | 9973 (1.9) | 17 802 (2.4) | 45 488 (6.4) | |
| Others | 8655 (1.6) | 20 652 (2.8) | 31 723 (4.5) | |
| Infant sex | ||||
| Male | 282 468 (51.7) | 394 313 (51.7) | 378 057 (51.3) | 0.004 |
| Female | 263 564 (48.3) | 368 012 (48.3) | 358 741 (48.7) | |
| Male/female ratio | 1.07 | 1.07 | 1.05 | |
| Gestational age at birth (weeks) | ||||
| <32 (very preterm) | 4013 (0.7) | 4871 (0.6) | 5637 (0.8) | 0.08 |
| 32–36 (moderate–late preterm) | 26 860 (5.0) | 35 716 (4.7) | 42 049 (5.7) | |
| 37–41 (term) | 497 387 (92.3) | 691 779 (90.9) | 679 439 (92.4) | |
| >41 (post-term) | 10 685 (2.0) | 28 743 (3.8) | 8583 (0.9) | |
| Birth weight (g) | ||||
| Mean (±) | 3262.7 (506.56) | 3229.3 (498.66) | 3197.3 (491.23) | |
| <1500 | 3722 (0.7) | 5150 (0.7) | 5073 (0.7) | 0.04 |
| 1500–2499 | 26 366 (4.8) | 40 346 (5.3) | 42 268 (5.7) | |
| 2500–3999 | 482 616 (88.4) | 678 757 (89.0) | 658 970 (89.4) | |
| >4000 | 33 328 (6.1) | 38 072 (5.0) | 30 487 (4.1) | |
*The p value for the comparison of the three periods using the χ2 test or analysis of variance, as appropriate, is <0.001 for all variables.