Table 2.
Baseline characteristics by smoking status for singleton births in the MATEX cohort (1991–2016)
| All | Non-smoker | Quit smoking during first trimester | Continued smoking after first trimester | |
| 1 376 778 | 84.5% (1 163 225) | 3.5% (47 819) | 12% (165 734) | |
| Mother | ||||
| Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | |
| Age (years) | 29.39 (5.34) | 29.78 (5.16) | 27.18 (5.43) | 27.3 (5.83) |
| Parity (nulliparous) | 59.5 (818 294) | 39.4 (458 010) | 58.8 (28 097) | 43.2 (71 629) |
| Marital status (married or partnership) | 62 (846 557) | 66.8 (771 065) | 35.9 (17 039) | 35.7 (58 453) |
| Socioeconomic status | % (count) | % (count) | % (count) | % (count) |
| Upper white collar worker | 14.9 (205 770) | 16.8 (195 402) | 6.4 (3081) | 4.4 (7287) |
| Lower white collar worker | 36.4 (501 780) | 37.4 (435 623) | 30.9 (14 786) | 31 (51 371) |
| Blue collar worker | 15.1 (207 962) | 13.2 (153 567) | 19.2 (9189) | 27.3 (45 206) |
| Other | 16.8 (231 481) | 16.3 (189 157) | 17.2 (8229) | 20.6 (34 095) |
| Missing | 16.7 (229 785) | 16.3 (189 476) | 26.2 (12 534) | 16.8 (27 775) |
| Child | ||||
| Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | |
| Gestational age (days) | 278.66 (12.05) | 278.74 (11.85) | 279.34 (12.11) | 277.87 (13.29) |
| Birth weight (g) | 3549.45 (542.2) | 3573.19 (536.38) | 3540.62 (535.37) | 3385.36 (556.1) |
| Body length (cm) | 50.21 (2.43) | 50.32 (2.4) | 50.12 (2.39) | 49.5 (2.59) |
| Head circumference (cm)* | 34.94 (1.64) | 34.99 (1.62) | 34.91 (1.65) | 34.55 (1.71) |
| Preterm birth | % (count) | % (count) | % (count) | % (count) |
| Preterm birth (<37 weeks) | 4.3 (58 828) | 4.1 (47 775) | 4.3 (2040) | 5.4 (9013) |
| Low/High birth weight | % (count) | % (count) | % (count) | % (count) |
| Low birth weight (<2500 g) | 3.0 (40 006) | 2.7 (30 443) | 3.0 (1387) | 5.0 (8176) |
| High birth weight (>4500 g) | 3.1 (41 054) | 3.3 (37 165) | 2.8 (1313) | 1.6 (2576) |
| Small for gestational age (<10th percentile) | % (count) | % (count) | % (count) | % (count) |
| Weight | 11.5 (158 817) | 10.4 (120 800) | 13.6 (6483) | 19.1 (31 534) |
| Body length | 6.0 (81 869) | 5.2 (60 003) | 7.0 (3345) | 11.2 (18 521) |
| Head circumference (cm)* | 10.9 (69 350) | 10.1 (54 321) | 13.3 (4675) | 16.4 (10 354) |
| Abnormal body proportions | % (count) | % (count) | % (count) | % (count) |
| High ponderal index | 11.0 (136 918) | 11.1 (116 902) | 11.8 (5111) | 10.1 (14 905) |
| Low brain-to-body ratio* | 11.1 (63 520) | 11.2 (54 554) | 12.5 (3968) | 9.2 (4998) |
| High head-to-length ratio* | 9.6 (60 358) | 9.8 (49 830) | 8.9 (3560) | 8.3 (6960) |
*Available since 1 January 2004.