Table 2.

Odds ratios (ORs)^a for thyroid cancer risk in offspring in relation to maternal, paternal, and birth characteristics and maternal and neonatal medical conditions

	Cases (n=2,437)	Controls (n=24,362)	OR	95% CI
Maternal characteristics
Age at birth (years)
<25	891 (37%)	8,694 (36%)	1·00	Reference
25-29	886 (36%)	8,676 (36%)	0·99	0·90-1·10
30-39	620 (25%)	6,611 (27%)	0·91	0·82-1·02
40+	40 (2%)	380 (2%)	1·02	0·73-1·43
Missing	0 (0%)	1 (0%)
Age at birth (per year)	2,437 (100%)	24,361 (100%)	0·99	0·99-1·00
Smoking during pregnancy
No	367 (15%)	3,826 (16%)	1·00	Reference
Yes	123 (5%)	1,150 (5%)	1·12	0·90-1·40
Missing	1,947 (80%)	19,386 (80%)
Marital status
Married/co-inhabitant	1,909 (78%)	19,196 (79%)	1·00	Reference
Single/widowed/divorced	444 (18%)	4,386 (18%)	1·02	0·90-1·14
Missing	84 (3%)	780 (3%)
Paternal characteristics
Age at birth (per year)	978 (40%)	9,791 (40%)	1·00	0·99-1·01
Missing	1,459 (60%)	14,571 (60%)
Birth characteristics
Preterm birth
No	2,316 (95%)	23,200 (95%)	1·00	Reference
Yes	116 (5%)	1,148 (5%)	1·01	0·83-1·23
Missing	5 (0·2%)	14 (0·1%)
Multiple birth
No	2,383 (98%)	23,919 (98%)	1·00	Reference
Yes	54 (2%)	443 (2%)	1·22	0·92-1·63
Cesarean delivery
No	2,254 (92%)	22,482 (92%)	1·00	Reference
Yes	181 (7%)	1,875 (8%)	0·96	0·82-1·13
Missing	2 (0·1%)	5 (0%)
Small-for-gestational age
No	2,262 (93%)	22,778 (94%)	1·00	Reference
Yes	70 (3%)	676 (3%)	1·04	0·81-1·34
Missing	105 (4%)	908 (4%)
Large-for-gestational age
No	2,275 (93%)	22,932 (94%)	1·00	Reference
Yes	57 (2%)	522 (2%)	1·10	0·83-1·45
Missing	105 (4%)	908 (4%)
Birth weight (g)
<1,500	7 (0·3%)	88 (0·4%)	0·85	0·39-1·84
1,500-2,499	89 (4%)	932 (4%)	1·02	0·81-1·27
2,500-3,499	1,096 (45%)	11,708 (48%)	1·00	Reference
3,500-4,499	1,171 (48%)	11,016 (45%)	1·14	1·04-1·24
4,500+	53 (3%)	514 (2%)	1·21	0·93-1·58
Missing	9 (0·4%)	45 (0·2%)
Birth weight (per kg)	2,428 (100%)	24,319 (100%)	1·14	1·05-1·23
Birth order
1	1,009 (41%)	9,756 (40%)	1·00	Reference
2	897 (37%)	8,569 (35%)	1·01	0·92-1·11
3	354 (15%)	3,973 (16%)	0·86	0·76-0·98
4	104 (4%)	1,330 (5%)	0·75	0·61-0·93
5+	72 (3%)	716 (3%)	0·97	0·75-1·24
Missing	1 (0%)	18 (0·1%)
Maternal conditions diagnosed before pregnancy
Diabetes	15 (0·6%)	89 (0·4%)	1·69	0·98-2·93
Hypertension	2 (0·1%)	22 (0·1%)	0·90	0·21-3·85
Maternal conditions diagnosed before/during pregnancy (Denmark only)
Hypothyroidism	38 (10%)	24 (0·6%)	18·1	10·5-31·2
Hyperthyroidism	27 (7%)	24 (0·6%)	11·9	6·8-20·9
Goiter	115 (29%)	30 (0·8%)	67·4	39·9-114
Thyroiditis	<5b	<5b	3·33	0·90-12·3
Benign thyroid neoplasms	<5b	<5b	22·5	6·93-73·1
Maternal conditions diagnosed during pregnancy
Gestational hypertension (yes vs. no)	31 (1%)	402 (2%)	0·77	0·53-1·11
Hyperemesis (yes vs. no)	23 (1%)	185 (1%)	1·24	0·81-1·92
Pregnancy anemia (yes vs. no)	20 (1%)	217 (1%)	0·92	0·58-1·46
Gestational diabetes (yes vs. no)	9 (0·4%)	72 (0·3%)	1·25	0·62-2·52
Placental abruption (yes vs. no)	7 (0·3%)	86 (0·4%)	0·81	0·37-1·76
Placenta previa (yes vs. no)	6 (0·2%)	69 (0·3%)	0·87	0·38-2·01
Preeclampsia/eclampsia (yes vs. no)	32 (0·1%)	337 (1%)	1·03	0·78-1·35
Postpartum hemorrhage (yes vs. no)	132 (5%)	1,047 (4%)	1·28	1·06-1·55
Neonatal conditions diagnosed in the first year after birth
Congenital hypothyroidism (yes vs. no)	5 (0·2%)	11 (0·04%)	4·55	1·58-13·1
Neonatal jaundice (yes vs. no)	27 (1%)	226 (1%)	1·20	0·80-1·81

NE= not estimable

^aFrom conditional logistic regression models, conditioned on birth year (of the case), sex, country, and county of birth

^bNumbers suppressed due to <5 cases and/or controls