Table 1 The association between the risk factors and development of OF

171 (53)

204 (51)

1.081 (0.806–1.450)

0.60354

1.007 (0.742–1.367)

0.964131

42 (13)

28 (7)

1.986 (1.201–3.283)

0.007475

1.339 (0.761–2.355)

0.311026

119 (36)

93 (23)

1.926 (1.393–2.662)

0.00735

1.854 (1.329–2.586)

0.0275

36 (11)

32 (8)

1.443 (0.874–2.380)

0.151417

1.307 (0.773–2.211)

0.318197

122 (38)

124 (31)

1.358 (0.997–1.850)

0.05254

1.339 (0.971–1.847)

0.074891

92 (29)

88 (22)

1.412 (1.007–1.980)

0.045517

1.293 (0.901–1.856)

0.162789

Maternal age (years)

< 25

43 (14)

48 (12)

1.483 (0.904–2.432)

0.118696

1.608 (0.952–2.717)

0.075617

26–30 (reference)

87 (27)

136 (34)

1

–

1

-

30–35

102 (31)

132 (33)

1.063 (0.939–1.204)

0.335031

1.062 (0.931–1.213)

0.369834

> 35

91 (28)

84 (21)

1.151 (1.042–1.272)

0.005646

1.139 (1.027–1.264)

0.01355

Paternal age (years)

< 25

29 (9)

44 (11)

1.023 (0.584–1.792)

0.93643

1.092 (0.602–1.982)

0.771544

26–30 (reference)

67 (21)

104 (26)

1

–

1

–

30–35

122 (38)

144 (36)

1.098 (0.964–1.251)

0.158797

1.098 (0.958–1.260)

0.179591

> 35

105 (32)

108 (27)

1.106 (0.998–1.225)

0.053716

1.105 (0.993–1.230)

0.067299

Birth order

1st (reference)

158 (49)

156 (39)

1

–

1

–

2nd

83 (26)

140 (35)

0.760 (0.638–0.906)

0.002204

0.789 (0.656–0.948)

0.011335

3rd

51 (16)

72 (18)

0.887 (0.771–1.021)

0.096105

0.914 (0.791–1.057)

0.225932

4th and higher

31 (9)

32 (8)

0.997 (0.870–1.142)

0.963656

0.988 (0.856–1.142)

0.872614

323(100)

400 (100)

–

–-

–

–