Table 2 Descriptive statistics
Measure | Statistics | Person- years of observation | |
|---|---|---|---|
Number of VPT Children | 5587 | 13,915 | |
Mean (sd) Birth year | 2005 (2.6) | 13,915 | |
Sex | # (%) Boy | 2881 (51.6%) | 7136 |
Gestational age | # (%) 22–24 weeks GA | 198 (3.7%) | 495 |
# (%) 25–26 weeks GA | 533 (9.9%) | 1335 | |
# (%) 27–28 weeks GA | 1029 (19.1%) | 2565 | |
# (%) 29–30 weeks GA | 1716 (31.8%) | 4298 | |
# (%) 31+ weeks GA | 1922 (35.6%) | 4725 | |
# (%) Missing GAa | 189 (3.4%) | 498 | |
Birth weight | Mean (sd) Birth weight | 1275.6 (378.8) | 13,592 |
# (%) Missing birth weigha | 115 (2.1%) | 323 | |
# (%) Small weight for GA | 1575 (29.2%) | 3875 | |
# (%) Missing weight for GAa | 201 (3.6%) | 534 | |
Malformation at birth | # (%) Has Q-diagnosis | 1183 (21.2%) | 2903 |
Apgar score at 5 min | Mean (sd) Apgar score 5 min | 8.3 (1.7) | 13,592 |
# (%) Missing Apgar score 5 mina | 80 (1.4%) | 323 | |
Multiple birth | # (%) Multiple birth | 1658 (29.7%) | 4151 |
# (%) First in multiple birth | 4718 (84.4%) | 11,726 | |
Parity | # (%) No previous children | 2972 (55.3%) | 7268 |
# (%) 1 previous child | 2405 (44.7%) | 6042 | |
# (%) Missing parity | 210 (3.8%) | 605 | |
Age of mother | Mean (sd) | 30.5 (5.5) | 13,915 |
Health status of mother | # (%) Chronic hypertension | 124 (2.2%) | 302 |
# (%) Bleeding any time in pregnancy | 798 (14.3%) | 1937 | |
# (%) Hellp syndrome | 197 (3.5%) | 500 | |
# (%) Any previous abortion | 1323 (23.7%) | 3296 | |
Highest education | # (%) Primary school | 851 (17.9%) | 2199 |
among maternal grandparents | # (%) Secondary education | 2765 (58.1%) | 6937 |
# (%) University education | 1139 (24.0%) | 2824 | |
# (%) Missing grandparents education levela | 832 (14.9%) | 1955 | |
Immigration status | # (%) Non-Norwegian native | 935 (16.7%) | 2184 |
Civil status (at birth) | # (%) Single/separated/divorced | 525 (9.5%) | 1218 |
# (%) Married/Cohabiting | 4994 (90.5%) | 12,521 | |
# (%) Missing civil statusa | 68 (1.2%) | 175 | |
Mothers’ education | # (%) Primary school | 1265 (24.7%) | 3159 |
(2 years before birth) | # (%) Secondary education | 1949 (38.1%) | 4982 |
# (%) University education | 1908 (37.3%) | 4678 | |
# (%) Missing educationa | 465 (8.3%) | 1096 | |
Income (1 year before birth) | Mean (sd) in thousands | 290.4 (205.7) | 13,424 |
# (%) Missing incomea | 206 (3.7%) | 491 | |
Age of father (at birth) | Mean (sd) | 33.5 (6.7) | 13,703 |
# (%) Missing age of fathera | 92 (1.6%) | 212 | |
Geography (at birth) | Mean (sd) Travel time to hospital | 24.9 (32.5) | 13,915 |
Hospital region (at birth) | # (%) South-Eastern health authority | 3059 (54.8%) | 7581 |
# (%) Western health authority | 1254 (22.4%) | 3098 | |
# (%) Central health authority | 754 (13.5%) | 1930 | |
# (%) Northern health authority | 520 (9.3%) | 1307 |