Introduction
Methods
Study samples
MoBa pregnancy cohort and nested case–control sample
Register-based cohort
Exposures
MoBa pregnancy cohort: questionnaire data on parental smoking
Nested case–control sample: cotinine in cord blood
Register-based cohort: maternal smoking recorded in the Medical Birth Registry of Norway
Other variables
Genotyping for celiac disease-associated risk markers
Statistical analyses
Ethics
Results
MoBa pregnancy cohort: questionnaire data on parental smoking
All | Maternal smoking in pregnancy | |||
---|---|---|---|---|
No smoking | Smoking < 18 preg. weeks | Smoking ≥ 18 preg. weeks | ||
n (%) | 94,019 (100) | 74,246 (79.0) | 12,272 (13.1) | 7501 (8.0) |
Celiac disease, n (%) | 1035 (1.1) | 851 (1.1) | 132 (1.1) | 52 (0.7) |
Calendar year of birth, median (range) | 2005 (2000–2009) | 2005 (2000–2009) | 2005 (2000–2009) | 2004 (2000–2009) |
Girls, n (%) | 45,879 (48.8) | 36,242 (48.8) | 5960 (48.6) | 3677 (49.0) |
Birth weight (gram), median (IQR) | 3600 (3250–3940) | 3600 (3260–3940) | 3635 (3290–3990) | 3498 (3130–3830) |
Gestational age (weeks), median (IQR) | 40 (39–41) | 40 (39–41) | 40 (39–41) | 40 (39–41) |
Cesarean delivery, n (%) | 13,903 (14.8) | 10,643 (14.3) | 2018 (16.4) | 1242 (16.6) |
Duration of full breastfeeding, n (%) | ||||
< 3 months | 31,987 (34.0) | 23,682 (31.9) | 4872 (39.7) | 3433 (45.8) |
3–5 months | 27,243 (29.0) | 20,814 (28.0) | 3886 (31.7) | 2543 (33.9) |
≥ 5 months | 34,789 (37.0) | 29,750 (40.1) | 3514 (28.6) | 1524 (20.3) |
Child’s infections age 0–6 months, median (IQR) | 1 (0–2) | 1 (0–2) | 1 (0–2) | 1 (0–2) |
Parity, n (%) | ||||
0 [first child] | 42,708 (45.4) | 32,654 (44.0) | 6749 (55.0) | 3305 (44.1) |
1 | 33,255 (35.4) | 26,989 (36.4) | 3741 (30.5) | 2525 (33.7) |
≥ 2 | 18,056 (19.2) | 14,603 (19.7) | 1782 (14.5) | 1671 (22.3) |
Maternal age at delivery, median (IQR) | 30 (27–33) | 31 (28–33) | 29 (26–32) | 29 (25–33) |
Maternal education level, n (%) | ||||
≤ 9 years | 7074 (7.5) | 3777 (5.1) | 1387 (11.3) | 1910 (25.5) |
10–12 years | 27,541 (29.3) | 19,203 (25.9) | 4780 (39.0) | 3557 (47.4) |
≥ 13 years | 59,404 (63.2) | 51,266 (69.0) | 6105 (49.7) | 2034 (27.1) |
Maternal occupation, n (%) | ||||
Sick leave/studying | 7690 (8.2) | 5350 (7.2) | 1296 (10.6) | 1044 (13.9) |
Unemployed | 5854 (6.2) | 4221 (5.7) | 716 (5.8) | 916 (12.2) |
Employed | 80,475 (85.6) | 64,674 (87.1) | 10,260 (83.6) | 5541 (73.9) |
Maternal annual income (NOK), n (%) | ||||
< 200,000 | 27,686 (29.4) | 19,718 (26.6) | 4300 (35.0) | 3669 (48.9) |
200,000–399,999 | 55,425 (59.0) | 45,031 (60.7) | 6964 (56.8) | 3429 (45.7) |
≥ 400,000 | 10,908 (11.6) | 9497 (12.8) | 1008 (8.2) | 403 (5.4) |
Maternal type 1 diabetes, n (%) | 528 (0.6) | 400 (0.5) | 70 (0.6) | 58 (0.8) |
Maternal celiac disease, n (%) | 1002 (1.1) | 827 (1.1) | 118 (1.0) | 57 (0.8) |
Maternal infections in pregnancy, median (IQR) | 1 (0–2) | 1 (0–2) | 1 (0–2) | 1 (0–2) |
Paternal age at delivery, n (%) | ||||
≤ 29 years | 25,563 (27.2) | 18,494 (24.9) | 4333 (35.3) | 2737 (36.5) |
30–34 years | 36,565 (38.9) | 29,693 (40.0) | 4499 (36.7) | 2373 (31.6) |
≥ 35 years | 31,890 (33.9) | 26,060 (35.1) | 3440 (28.0) | 2391 (31.9) |
Paternal education level, n (%) | ||||
≤ 9 years | 10,059 (10.7) | 6137 (8.3) | 1893 (15.4) | 2029 (27.0) |
10–12 years | 38,009 (40.4) | 28,033 (37.8) | 5230 (48.3) | 4045 (53.9) |
≥ 13 years | 45,951 (48.9) | 40,075 (54.0) | 4449 (36.3) | 1427 (19.0) |
Paternal occupation, n (%) | ||||
Sick leave/studying | 5142 (5.5) | 3732 (5.0) | 806 (6.6) | 604 (8.1) |
Unemployed | 1710 (1.8) | 1086 (1.5) | 274 (2.2) | 350 (4.7) |
Employed | 87,167 (92.7) | 69,428 (93.5) | 11,192 (91.1) | 6547 (87.3) |
Paternal annual income (NOK), n (%) | ||||
< 200,000 | 10,619 (11.3) | 7423 (10.0) | 1730 (14.1) | 1465 (19.5) |
200,000–399,999 | 52,250 (55.6) | 40,477 (54.5) | 7170 (58.4) | 4602 (61.4) |
≥ 400,000 | 31,150 (33.1) | 26,345 (35.5) | 3371 (27.5) | 1433 (19.1) |
Paternal type 1 diabetes, n (%) | 609 (0.6) | 473 (0.6) | 87 (0.7) | 49 (0.7) |
Paternal celiac disease, n (%) | 312 (0.3) | 260 (0.3) | 28 (0.2) | 24 (0.3) |
Paternal smoking in pregnancy, n (%) | 20,689 (22.0) | 10,499 (14.1) | 5384 (43.9) | 4804 (64.0) |
Parental cohabitation, n (%) | 90,933 (96.7) | 72,597 (97.8) | 11,626 (94.7) | 6710 (89.4) |
Celiac disease n = 381 (%) | Random controls n = 529 (%) | Model I | Model II | Model III | ||||
---|---|---|---|---|---|---|---|---|
aOR | 95% CI | aOR | 95% CI | aOR | 95% CI | |||
Trichotomous cotinine groups [“Maternal exposure level”] | ||||||||
Cotinine < 1.0 nmol/L [“No smoke exposure”] | 329 (86.4) | 433 (81.9) | Ref. | Ref. | Ref. | |||
Cotinine 1.0–29.9 nmol/L [“ETS/occasional smoking”] | 32 (8.4) | 49 (9.3) | 0.84 | 0.53–1.33 | 0.84 | 0.53–1.35 | 0.83 | 0.51–1.36 |
Cotinine ≥ 30.0 nmol/L [“Daily smoking”] | 20 (5.2) | 47 (8.9) | 0.54 | 0.31–0.95 | 0.55 | 0.31–0.98 | 0.60 | 0.33–1.10 |
Per change in cotinine groupA | 0.76 | 0.59–0.97 | 0.77 | 0.60–0.98 | 0.79 | 0.60–1.03 |
Nested case–control sample: cotinine in cord blood
Register-based cohort: maternal smoking recorded in the Medical Birth Registry of Norway
All | Maternal smoking in pregnancyA | ||||
---|---|---|---|---|---|
No smoking | Smoking 10 preg. weeks | Smoking 36 preg. weeks | Inconsistent dataB | ||
n (%) | 536,861 (100) | 462,816 (86.2) | 27,331 (5.1) | 45,514 (8.5) | 1199 (0.2) |
Celiac disease, n (%) | 1919 (0.4) | 1667 (0.4) | 106 (0.4) | 143 (0.3) | 4 (0.3) |
Calendar year of birth, median (IQR) | 2008 (2004–2012) | 2008 (2004–2012) | 2007 (2004–2012) | 2008 (2004–2012) | 2008 (2004–2012) |
Girls, n (%) | 261,281 (48.7) | 225,263 (48.7) | 13,317 (48.7) | 22,137 (48.6) | 564 (47.1) |
Birth weight (g), median (IQR) | 3530 (3180–3880) | 3550 (3200–3890) | 3540 (3180–3890) | 3355 (3000–3700) | 3460 (3110–3800) |
Gestational age (weeks), median (IQR) | 40 (39–41) | 40 (39–41) | 40 (39–41) | 39 (38–40) | 40 (38–40) |
Cesarean delivery, n (%) | 90,021 (16.8) | 76,993 (16.6) | 4904 (17.9) | 7905 (17.4) | 219 (18.3) |
Parity, n (%) | |||||
0 [first child] | 226,246 (42.1) | 192,051 (41.5) | 15,416 (56.4) | 18,323 (40.3) | 455 (38.0) |
1 | 191,690 (35.7) | 168,788 (36.5) | 7705 (28.2) | 14,751 (32.4) | 447 (37.3) |
≥ 2 | 118,924 (22.2) | 101,977 (22.0) | 4210 (15.4) | 12,440 (27.3) | 297 (24.8) |
Maternal age at delivery, median (IQR) | 30 (26–33) | 30 (27–34) | 27 (23–32) | 28 (23–32) | 29 (25–33) |
Maternal education level, n (%) | |||||
≤ 9 years | 92,526 (17.2) | 63,393 (13.7) | 7767 (28.4) | 20,989 (46.1) | 377 (31.5) |
10–12 years | 160,207 (29.8) | 130,971 (28.3) | 10,960 (40.1) | 17,818 (39.1) | 459 (38.3) |
≥ 13 years | 284,127 (52.9) | 268,453 (58.0) | 8604 (31.5) | 6707 (14.7) | 363 (30.3) |
Maternal diabetes, n (%) | |||||
Pre-gestational | 3990 (0.7) | 3359 (0.7) | 215 (0.8) | 408 (0.9) | 8 (0.7) |
Gestational | 8433 (1.6) | 7304 (1.6) | 434 (1.6) | 672 (1.5) | 22 (1.9) |
Paternal age at delivery, median (IQR) | 32 (29–37) | 33 (29–37) | 30 (26–35) | 31 (26–36) | 31 (27–36) |