Table 1 Characteristics of the training and validation cohorts(N = 2457)

Female age (years)

32.50 ± 3.60

32.62 ± 3.74

BMI (kg/m²)

23.44 ± 3.78

23.57 ± 3.82

AMH (ng/ml)

3.99 ± 3.10

4.19 ± 3.32

Baseline FSH (IU/L)

6.11 ± 2.30

6.05 ± 2.46

Duration of infertility (years)

4.07 ± 3.07

4.34 ± 3.34

Type of infertility, n(%)

 Primary infertility

991 (53.48%)

318 (52.65%)

Secondary infertility

862 (46.52%)

286 (47.35%)

Infertility diagnosis, n(%)

 Female factor

1104 (59.58%)

370 (61.26%)

 Male factor

226 (12.20%)

70 (11.59%)

 Multiple factors

461 (24.88%)

149 (24.67%)

 Unexplained and other

62 (3.35%)

15 (2.48%)

FET protocols, n(%)

 Artificial cycle

225 (12.14%)

62 (10.26%)

 Natural cycle

1628 (87.86%)

542 (89.74%)

Type of embryos transferred, n(%)

 Cleavage embryo

1009 (54.45%)

321 (53.15%)

 Blastocyst

844 (45.55%)

283 (46.85%)

No. of embryos transferred, n(%)

 1

511 (27.58%)

169 (27.98%)

 2

1342 (72.42%)

435 (72.02%)

Endometrial thickness (cm)

1.00 ± 0.22

0.99 ± 0.20

Endometrial pattern, n (%)

 Type A

639 (34.48%)

190 (31.46%)

 Type non-A

1214 (65.52%)

414 (68.54%)

VI

5.68 ± 3.67

5.56 ± 3.51

FI

32.96 ± 5.08

32.87 ± 5.15

RI

0.51 ± 0.09

0.51 ± 0.09

PI

0.75 ± 0.21

0.75 ± 0.20

No. of Sub-endometrial blood, n (%)

 A

87 (4.70%)

31 (5.13%)

 B

1076 (58.07%)

356 (58.94%)

 C

690 (37.24%)

217 (35.93%)

Endometrial blood flow classification, n (%)

 I

136 (7.34%)

53 (8.77%)

 II

1660 (89.58%)

531 (87.91%)

 III

57 (3.08%)

20 (3.31%)

Pregnancy outcomes

 Non-pregnancy

686 (37.02%)

229 (37.91%)

 Pregnancy

1167 (62.98%)

375 (62.09%