Table 1 Clinical characteristics of the PCOS women with singleton and twin births (Median ± IQR (range) or n (%))

Maternal age, years

31.0 (28.0, 33.0)

30.0 (28.0, 32.0)

0.06

Preconception BMI, kg/m²

23.9 (21.3, 27.0)

24.0 (21.5, 27.3)

0.59

AFC, n

16.0 (11.0, 21.0)

16.0 (12.0, 22.0)

0.24

Testosterone, nmol/L

0.7 (0.7, 1.1)

0.7 (0.7, 1.0)

0.90

AMH, ng/mL

4.9 (2.9, 7.4)

5.2 (3.5, 8.2)

0.07

Duration of infertility, years

3.0 (2.0, 4.0)

3.0 (2.0, 5.0)

0.81

T4, μg/dL

7.9 (7.0, 9.0)

8.2 (7.2, 9.2)

0.11

FT4, ng/dL

1.3 (1.2, 1.4)

1.3 (1.2, 1.4)

0.18

TSH, μIU/mL

2.1 (1.6, 2.9)

2.1 (1.6, 3.0)

0.74

TGAb, U/mL

15.6 (15.0, 24.6)

16.0 (15.0, 27.5)

0.54

TPOAb, U/mL

30.0 (28.0, 40.7)

29.4 (28.0, 43.5)

0.98

Positive TGAb^b

No

308 (85.3)

105 (84.0)

0.72

Yes

53 (14.7)

20 (16.0)

Positive TPOAb^b

No

319 (88.4)

110 (88.0)

0.91

Yes

42 (11.6)

15 (12.0)

Infertility type

Primary

263 (72.9)

102 (81.6)

0.05

Secondary

98 (27.1)

23 (18.4)

Ovarian stimulation regimen

GnRH antagonist

274 (75.9)

90 (72.0)

0.55

Long GnRHa

80 (22.2)

31 (24.8)

Others^bc

7 (1.9)

4 (3.2)

Insemination technique

IVF

265 (73.4)

86 (68.8)

0.35

ICSI

96 (26.6)

39 (31.2)

Timing of embryo transfer

Day 3

344 (95.3)

124 (99.2)

0.16

Day 5

12 (3.3)

1 (0.8)

Day 6

5 (1.4)

0 (0.0)

Transferred embryos number, n

1

49 (13.6)

1 (0.8)

 < 0.001

2

312 (86.4)

124 (99.2)

Gestational age, weeks

 < 37

330 (91.4)

63 (50.4)

 < 0.001

37 − 42

31 (8.6)

62 (49.6)

Delivery mode

Vaginal delivery

165 (45.7)

13 (10.4)

 < 0.001

Caesarean

196 (54.3)

112 (89.6)

Neonatal sex

Male

177 (49.0)

128 (51.2)

0.62

Female

184 (51.0)

122 (48.8)

Birth weight, g

 < 2500

17 (4.7)

130 (52.0)

 < 0.001

2500 − 4000

320 (88.6)

120 (48.0)

 ≥ 4000

24 (6.6)

0 (0.0)