Table 1 Characteristics of women undergoing the first fresh embryo transfer cycle

Number of cases

N = 8144

N = 182

N = 5378

N = 14

Female age y^a

33.4 (5.1)

31.8 (3.8)

31.7 (4.1)

31.8 (4.7)

< 0.001

0.93

Male age y^a

34.8 (6.1)

32.5 (4.5)

33.1 (5.2)

35.1 (5.8)

< 0.001

0.09

BMI kg/m^2a

23.0 (3.6)

23.1 (3.8)

22.7 (3.5)

23.7 (3.0)

< 0.001

0.09

Infertile age y^a

3.0 (2.0-5.0)

3.0 (2.0-4.0)

3.0 (1.0-4.0)

3.5 (2.0-5.0)

< 0.001

0.99

Ectopic history

596 (7%)

26 (14%)

477 (9%)

3 (21%)

< 0.001

0.01

Ovulatory dysfunction

898 (11%)

33 (18%)

520 (10%)

1 (7%)

< 0.001

< 0.001

Endometriosis

372 (5%)

7 (4%)

264 (5%)

2 (14%)

0.26

0.51

Tubal

5054 (62%)

98 (54%)

3232 (60%)

6 (43%)

0.01

0.09

Male

3989 (49%)

78 (43%)

2766 (51%)

7 (50%)

0.01

0.02

Primary infertility

4502 (55%)

90 (49%)

3085 (57%)

5 (36%)

0.01

0.03

Parity

771 (9%)

10 (5%)

389 (7%)

1 (7%)

< 0.001

0.37

GnRH antagonist

4947 (61%)

127 (70%)

2706 (50%)

5 (36%)

< 0.001

< 0.001

Gn days^a

11.1 (2.5)

10.9 (2.5)

11.4 (2.5)

12.1 (3.6)

< 0.001

< 0.01

Gn doses IU^a

2921 (1209)

2556 (1021)

2773 (1154)

3079 (970)

< 0.001

0.01

Sperm donor

180 (2%)

6 (3%)

182 (3%)

0 (0%)

< 0.001

0.95

EMT mm^a

10.6 (1.7)

10.1 (1.5)

11.1 (1.6)

10.5 (1.6)

< 0.001

< 0.001

Thin endometrium

211 (3)%

7 (4%)

47 (1%)

0 (0%)

< 0.001

< 0.001

Oocyte yield ^a

9 (5)

11 (4)

11 (5)

10 (4)

< 0.001

0.89

Estradiol level^a

5609 (3847-8418)

6259 (4714-9602)

6072 (4214-9170)

5521 (3487-9012)

< 0.001

0.24

ICSI

2619 (32%)

42 (23%)

1772 (33%)

5 (36%)

0.04

< 0.01

Blastocyst transfer

508 (6%)

8 (4%)

236 (4%)

0 (0%)

< 0.001

1.00

Single embryo transfer

1532 (19%)

19 (10%)

534 (10%)

0 (0%)

< 0.001

0.82

At least one poor-quality embryo transferred

401 (5%)

1 (1%)

140 (3%)

1 (7%)

< 0.001

0.08