Table 1 Test dataset characteristics. Double stratification of data by age (< 35; 35–37, 38–40, 41–43, > 43 years) and by different subgroups of maternal (uterus) age, oocyte age, and oocyte source (autologous and donor oocyte recipient). Odds ratio (OR) and P-values for the associations between each subgroup and fetal heartbeat (FH) rate is shown. Mean AI score per age category is also shown. All transferred embryos in this analysis had known FH clinical outcomes

Maternal (Uterus) Age

Transferred embryos (n)

285

196

180

183

142

FH + embryos (n)

135

103

89

86

79

FH rate (%)

[95% CI]

47.36 [41.5–53.2]

52.55 [45.5–59.60]

49.44 [42.10–56.80]

46.99 [39.70–54.30]

55.63 [47.40–63.90]

Age

(mean ± SD, years)

31.3 ± 2.76

36.0 ± 0.81

39.2 ± 0.78

41.9 ± 0.83

45.7 ± 1.71

OR

[95% CI]

0.90 [0.71–1.14]

1.23 [0.86–1.77]

1.09 [0.75–1.58]

0.99 [0.68–1.42]

1.39 [0.93–2.09]

P-value

0.374

0.264

0.662

0.937

0.108

AI score (mean ± SD)

6.24 ± 2.45

5.93 ± 2.43

5.98 ± 2.29

5.82 ± 2.66

6.38 ± 2.25

Oocyte Age

Transferred embryos (n)

669

155

84

59

20

FH + embryos (n)

369

81

28

11

3

FH rate (%)

[95% CI]

55.15

[51.40–58.90]

52.25 [44.30–60.20]

33.33 [23.00-43.60]

18.64 [8.41–28.90]

15.0

[0.0-32.10]

Age

(mean ± SD, years)

27.6 ± 4.78

35.9 ± 0.82

39.0 ± 0.79

41.7 ± 0.81

44.8 ± 0.76

OR

[95% CI]

1.230

[1.056–1.432]

0.890 [0.627–1.263]

0.407 [0.252–0.656]

0.186 [0.095–0.360]

0.143

[0.042–0.494]

P-value

0.007

0.513

< 0.001

< 0.001

0.002

AI score (mean ± SD)

6.50 ± 2.22

5.82 ± 2.45

4.99 ± 2.43

4.06 ± 2.79

4.33 ± 2.63

Autologous IVF Cycles

Transferred embryos (n)

254

155

84

59

20

FH + embryos (n)

113

81

28

11

3

FH rate (%)

[95% CI]

44.48 [38.30–50.60]

52.25 [44.30–60.20]

33.33 [23.00-43.60]

18.64 [8.41–28.90]

15.0

[0.0-32.10]

Age

(mean ± SD, years)

31.2 ± 2.82

35.9 ± 0.82

39.0 ± 0.79

41.7 ± 0.81

44.8 ± 0.76

OR

[95% CI]

0.80 [0.63–1.03]

1.37 [0.92–2.04]

0.62

[0.37–1.05]

0.29 [0.14–0.57]

0.22

[0.06–0.77]

P-value

0.079

0.127

0.073

< 0.001

0.017

AI score (mean ± SD)

6.12 ± 2.51

5.82 ± 2.45

4.99 ± 2.43

4.06 ± 2.79

4.33 ± 2.63

Donor Oocyte Recipient IVF Cycles

Transferred embryos (n)

31

41

96

124

122

FH + embryos (n)

22

22

61

75

76

FH rate (%)

[95% CI]

70.96 [54.00-87.90]

53.65 [37.70–69.60]

63.54 [53.70–73.30]

60.48 [51.80–69.20]

62.29 [53.60–71.00]

Oocyte age

(mean ± SD, years)

25.9 ± 3.75

25.8 ± 4.60

25.2 ± 4.40

25.0 ± 4.26

25.6 ± 4.45

Maternal age

(mean ± SD)

31.9 ± 2.08

36.2 ± 0.759

39.3 ± 0.771

42.0 ± 0.836

45.9 ± 1.78

OR

[95% CI]

2.44 [1.13–5.31]

0.47 [0.18–1.27]

0.713 [0.30–1.72]

0.62 [0.27–1.47]

0.68 [0.29–1.59]

P-value

0.023

0.138

0.451

0.283

0.370

AI score (mean ± SD)

7.25 ± 1.56

6.34 ± 2.34

6.86 ± 1.74

6.66 ± 2.14

6.72 ± 2.00