Table 2 Association between in-utero and newborn factors and differentiated thyroid cancer incidence in the Sister Study cohort.

From: In-utero and newborn factors and thyroid cancer incidence in adult women in the Sister Study cohort

Characteristic

 

Multivariable models

Total cohort, N (%)

DTC cases, N

Person-years

HRa

95% CIa

Maternal pregnancy characteristics

     

Pre-pregnancy or gestational diabetes

     

 Probably not/Definitely not

46,011 (96.0%)

230

562,673

1

—

 Definitely/Probably

432 (0.9%)

5

5198

2.36

0.97, 5.74

 Unknown

1470 (3.1%)

4

15,265

–

–

Gestational hypertension or hypertension-related disorders

     

 Probably not/Definitely not

39,918 (83.3%)

199

490,021

1

—

 Definitely/Probably

1634 (3.4%)

16

19,753

1.99

1.20, 3.32

 Unknownb

6361 (13.3%)

24

73,361

–

–

Morning sickness with vomiting

     

 Probably not/Definitely not

12,622 (26.3%)

69

157,858

1

—

 Definitely/Probably

16,953 (35.4%)

94

207,073

1.07

0.78, 1.46

 Unknownb

18,338 (38.3%)

76

218,204

–

–

Smoking during pregnancy

     

 Probably not/Definitely not

30,588 (63.8%)

154

373,485

1

—

 Definitely/Probably

14,212 (29.7%)

72

174,538

0.99

0.74, 1.31

 Unknownb

3113 (6.5%)

13

35,112

–

–

Household secondhand smoking during pregnancy

     

 Probably not/Definitely not

18,209 (38.0%)

104

224,258

1

—

 Definitely/Probably

25,430 (53.1%)

122

310,669

0.86

0.66, 1.12

 Unknownb

4274 (8.9%)

13

48,208

–

–

Time since last pregnancy

     

 First born

10,702 (22.3%)

57

130,433

1

—

 Equal or less than 2 years

17,181 (35.9%)

88

209,459

0.92

0.66, 1.30

 2–5 years

12,797 (26.7%)

66

157,276

0.91

0.64, 1.30

 More than 5 years

5274 (11.0%)

20

65,010

0.66

0.40, 1.11

 Unknownb

1959 (4.1%)

8

20,958

–

–

Time since last pregnancy (per year, continuous)c

45,954

174

431,744

0.97

0.91, 1.03

Age at delivery (years)

     

 <25 years

13,354 (27.9%)

70

160,261

1

—

 25–29 years

14,194 (29.6%)

74

174,458

0.95

0.68, 1.31

 30–34 years

10,862 (22.7%)

50

133,930

0.82

0.57, 1.19

 35+

8545 (17.8%)

41

104,668

0.86

0.58, 1.27

 Unknownb

958 (2.0%)

4

9817

-

-

Age at delivery (per year, continuous)

46,955

235

573,318

0.99

0.97, 1.01

Paternal pregnancy characteristics

     

Smoking during 3 months before conception

     

 Probably not/Definitely not

14,835 (31.0%)

78

183,156

1

—

 Definitely/Probably

29,089 (60.7%)

145

354,729

0.99

0.75, 1.30

 Unknownb

3989 (8.3%)

16

45,250

–

–

Age at delivery

     

 <25 years

6687 (14.0%)

34

79,488

1

—

 Between 25 and 29 years

12,802 (26.7%)

62

157,065

0.9

0.60, 1.37

 Between 30 and 34 years

12,174 (25.4%)

63

150,351

0.95

0.63, 1.44

 35+ years

15,032 (31.4%)

74

183,618

0.91

0.61, 1.37

 Unknownb

1218 (2.5%)

6

12,613

–

–

Age at delivery (per year, continuous)

46,695

233

570,522

1.00

0.98, 1.02

Birth and infancy characteristics

     

Birth weight (g)

     

 <2500

3562 (7.4%)

10

42,933

0.6

0.32, 1.14

 2500–3999

28,273 (59.0%)

140

349,938

1

—

 4000+

3150 (6.6%)

23

38,632

1.50

0.96, 2.33

 Unknownb

12,928 (27.0%)

66

151,632

-

-

Birth weight (per kg, continuous)

34,674

172

427,789

1.24

0.95, 1.60

Birth order

     

 First born

10,702 (22.3%)

57

130,433

1

—

 Second born

12,078 (25.2%)

61

148,388

0.91

0.63, 1.30

 Third born

9396 (19.6%)

43

115,772

0.81

0.54, 1.21

 Fourth born or more

13,778 (28.8%)

70

167,573

0.9

0.63, 1.30

 Unknownb

1959 (4.1%)

8

20,970

-

-

Birth order (per birth, continuous)

45,954

231

562,165

1.01

0.95, 1.08

Multiple birth

     

 Single birth

45,664 (95.3%)

230

557,281

1

—

 Multiple birth

1493 (3.1%)

6

18,210

0.8

0.36, 1.80

 Unknownb

756 (1.6%)

3

7644

–

–

Gestational age at birth

     

 Born post-term or <2 weeks before due date

18,956 (39.6%)

116

237,133

1

—

 Born 2 or more weeks before the due date

2778 (5.8%)

8

34,695

0.47

0.23, 0.97

 Unknownb

26,179 (54.6%)

115

311,308

–

–

Ever breastfed

     

 Probably not/Definitely not

22,246 (46.4%)

119

274,855

1

—

 Definitely/Probably

21,310 (44.5%)

104

259,040

0.97

0.74, 1.27

 <6 weeks

2241 (4.7%)

15

28,508

1.22

0.71, 2.08

 6 weeks–3 months

3175 (6.6%)

13

39,500

0.76

0.43, 1.35

 4–6 months

2933 (6.1%)

16

36,075

1.05

0.62, 1.76

 >6 months

4850 (10.1%)

21

58,399

0.86

0.53, 1.38

 Unknown durationb

8111 (16.9%)

39

96,558

–

–

 Unknownb

4357 (9.1%)

16

49,240

–

–

  1. HR Hazard Ratio, CI Confidence Interval.
  2. aMultivariable models used attained age as the timescale and were adjusted for race/ethnicity.
  3. bResults for “Unknown” categories are not shown.
  4. cIndividuals who were first born were excluded.
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