Table 1

Characteristics of the study population (n=7092), and comparative national population data (see online supplementary file 1)

 Age of motherNational data on ageMother primiparousNational data on primiparityEducation, university/collegeNational data on education
nMean (IPR*)Mean agePer centPer centPer centPer cent
Total709229 (23 to 36)†5355
Eastern Europe153228 (22 to 34)5567
 Russia60627 (21 to 34)2756NA72NA
 Croatia17430 (24 to 36)2859476244
 Poland50027 (21 to 32)2955506342
 Serbia13129 (25 to 34)2953515929
 Slovenia12132 (26 to 37)3050497143
Northern Europe218429 (23 to 35)‡5254
 Finland48329 (22 to 35)3042425448
 Iceland65§NA51384548
 Sweden70330 (23 to 36)3064456251
 Norway93329 (23 to 35)3049424855
Australia17531 (24 to 38)3149446256
Western Europe251931 (25 to 37)5549
 Austria5130 (23 to 36)3057484523
 Italy78732 (26 to 38)3162494526
 Switzerland46131 (26 to 37)3149NA4539
 France31930 (24 to 37)3054445847
 The Netherlands4730 (23 to 36)3140462344
 UK85430 (23 to 37)3054425346
Americas68228 (21 to 36)4652
 The USA23129 (21 to 37)NA46406558
 Canada18628 (21 to 34)3052436870
 South-American Countries26527 (20 to 34)NA42NA30NA
  • *Interpercentile range (IPR) calculated 10th to 90th percentile.

  • †Calculated based on 7028 values, because 64 values from Iceland were not available.

  • ‡Calculated based on 2120 values, because 64 values from Iceland were not available.

  • §Not shown because 64 values were not available.