Table 1

Maternal and infant characteristics of singleton live births in Portugal, 1995–2014

Variable1995–1999
n (%)
2000–2006
n (%)
2007–2014
n (%)
Effect size (Cohen's d)*
Total live births546 032 (26.7)762 325 (37.3)736 798 (36.0)
Maternal nationality
 Portugal530 430 (97.1)709 199 (93.0)663 963 (90.1)0.11
 Other country15 602 (2.9)53 126 (7.0)72 835 (9.9)
Paternal age, mean (±) years30.4 (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)
 ≤1937 710 (6.9)42 906 (5.6)29 734 (4.0)0.13
 20–34447 384 (81.9)605 099 (79.4)541 738 (73.5)
 ≥3560 938 (11.2)114 320 (15.5)165 326 (22.4)
Parity
 Primiparae292 274 (53.5)415 066 (54.5)399 175 (54.3)0.01
 Multiparae253 756 (46.5)347 038 (45.5)336 564 (45.7)
Maternal education
 Primary375 555 (68.8)420 124 (55.1)284 270 (39.2)0.24
 Secondary99 277 (18.2)179 741 (23.6)209 131 (28.8)
 Tertiary71 200 (13.0)162 220 (21.3)232 626 (32.0)
Maternal employment status
 Employed342 306 (62.7)544 958 (71.5)511 140 (70.8)0.18
 Unemployed24 088 (4.4)47 093 (6.2)93 950 (13.0)
 Others179 638 (32.9)169 635 (22.3)116 416 (16.1)
Paternal employment status
 Employed509 082 (96.5)707 149 (94.8)634 764 (89.2)0.13
 Unemployed9973 (1.9)17 802 (2.4)45 488 (6.4)
 Others8655 (1.6)20 652 (2.8)31 723 (4.5)
Infant sex
 Male282 468 (51.7)394 313 (51.7)378 057 (51.3)0.004
 Female263 564 (48.3)368 012 (48.3)358 741 (48.7)
 Male/female ratio1.071.071.05
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)
 <15003722 (0.7)5150 (0.7)5073 (0.7)0.04
 1500–249926 366 (4.8)40 346 (5.3)42 268 (5.7)
 2500–3999482 616 (88.4)678 757 (89.0)658 970 (89.4)
 >400033 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.