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Table 1 Characteristics of women undergoing fresh cycle

From: Risk factors for twin pregnancy in women undergoing double cleavage embryo transfer

variables

Twins

(n = 1511)

Singleton

(n = 4778)

No delivery

(n = 9170)

P valuea

Female age y

29.4 ± 3.2

30.2 ± 3.7

30.7 ± 4.3

< 0.001

  >35

41 (3%)

391 (8%)

1224 (13%)

 

  ≤35

1470 (97%)

4387 (92%)

7946 (87%)

 

Male age y

31.7 ± 4.3

32.1 ± 4.6

32.9 ± 5.3

< 0.001

  >35

244 (16%)

991 (21%)

2424 (26%)

 

  ≤35

1265 (84%)

3786 (79%)

6737 (74%)

 

Female BMI kg/m2

21.8 ± 2.7

21.9 ± 2.8

22.1 ± 2.9

< 0.001

  ≥25

191 (13%)

661 (13.8%)

1450 ± (16%)

0.24

  <25

1317 (87.3%)

4116 (86.2%)

7717 ± (84%)

 

Male BMI kg/m2

23.7 ± 3.7

23.7 ± 3.6

23.7 ± 3.6

0.88

  ≥25

487 (33%)

1573 (33%)

2936 (33%)

 

  <25

992 (67%)

3135 (67%)

6038 (67%)

 

Primary infertility

742 (49%)

2278 (48%)

4302 (47%)

0.25

FSH mIU/ml

7 (6–8)

7 (6–8)

7 (6–8)

0.44

LH mIU/ml

5 (3–6)

5 (3–6)

5 (3–6)

0.10

Estradiol pmol/l

113 (81–145)

111 (79–148)

114 (82–153)

0.008

Progesterone nmol/l

1.6 (1.1–2.3)

1.5 (1.1–2.1)

1.6 (1.1–2.2)

< 0.001

Total testosterone nmol/l

0.8 (0.5–1.1)

0.7 (0.5–1.1)

0.79 (0.5–1.1)

0.22

Reason for IVF

  Tubal factor

842 (56%)

2601 (54%)

4993 (54%)

0.64

  Ovulatory dysfunction

85 (5.6%)

316 (6.6%)

643 (7.0%)

0.12

  Male factor

447 (30%)

1586 (33%)

2960 (32%)

0.033

  Endometriosis

188 (12.4%)

571 (12.0%)

866 (9.4%)

< 0.001

  Down-regulation

   

< 0.001

  GnRH agonist

1310 (86.7%)

3671 (76.8%)

7185 (78.4%)

 

  GnRH antagonist

182 (12%)

1019 (21.3%)

1807 (19.7%)

 

  Other

19 (1.3%)

88 (1.8%)

178 (1.9%)

 

Sperm donor

27 (2.0%)

77 (2.1%)

108 (1.4%)

0.012

ICSI

392 (8.7%)

1392 (30.9%)

2723 (60.4%)

0.01

Poor-type endometrium

60 (4.8%)

253 (7.5%)

432 (6.0%)

0.001

Embryo quality

   

< 0.001

  GG

1360 (92.2%)

3864 (82.2%)

7010 (78.1%)

 

  GP

97 (6.6%)

663 (14.1%)

1257 (14.0%)

 

  PP

18 (1.2%)

175 (3.7%)

712 (7.9%)

 

  High education

703 (46.6%)

2276 (47.7%)

3792 (41.4%)

< 0.001

Smoking

   

0.275

  Yes

5 (0.3%)

27 (0.6%)

61 (0.7%)

 

  No

1505 (99.7%)

4747 (99.4%)

9102 (99.3%)

 

Endometrial thickness mm

11.3 ± 2.4

11.1 ± 2.4

10.7 ± 2.4

< 0.001

  Moderate

1288 (86%)

4068 (87%)

7938 (88%)

 

  Thin

18 (1%)

81 (2%)

271 (3%)

 

  Thick

184 (12%)

545 (12%)

824 (9%)

 

Total number of oocytes

11.4 ± 4.8

10.9 ± 4.9

10.8 ± 5.0

< 0.001

Ovarian response

   

< 0.001

  Moderate

1067 (71%)

3348 (70%)

6297 (69%)

 

  Poor

155 (10%)

639 (13%)

1349 (15%)

 

  High

289 (19%)

790 (17%)

1519 (17%)

 
  1. χ2, non-parametric test, or t test as appropriate. Data expressed with Mean ± SD or Median (IQR) or Number (percent) as appropriate. GG, two good-quality embryo; GP, one good-quality embryo and one poor-quality embryo; PP, two poor-quality embryo
  2. Notes: Poor-type endometrium: A multilayered endometrium consisting of prominent outer and midline hyperechogenic lines and inner hypoechogenic regions. Good quality embryos: Grade I-II embryos; Poor-quality embryos: Grade III-IV embryos. Thin endometrium: Endometrial thickness lower than 7 mm; Moderate endometrium: Endometrial thickness at 7–14 mm; Thick endometrium: Endometrial thickness higher than 14 mm. High education: A master degree or PhD degree. Poor ovarian response: 0–5 oocytes retrieved; Moderate ovarian response: 6–15 oocytes retrieved; High ovarian response: > 16 oocytes retrieved
  3. Sex hormones (FSH, LH, Progesterone, and Total testosterone) were measured on day 2–5 of menstrual cycle