Table 3 Cumulative Live Births and Pregnancy Outcomes (Intention-to-Treat Analysis)

From: Effect of single blastocyst-stage versus single cleavage-stage embryo transfer on cumulative live births in women with good prognosis undergoing in vitro fertilization: Multicenter Randomized Controlled Trial

Outcomes, No./total (%)

Blastocyst-stage embryo transfer group (n = 497)

Cleavage-stage embryo transfer group (n = 495)

Absolute difference (95% CI)a

Relative risk (95% CI)

P valueb

Primary outcome

Cumulative live birthsc

372 (74.8)

328 (66.3)

8.6 (2.9 to 14.2)

1.13 (1.04 to 1.22)

0.003

 Singleton live births

363 (73.0)

324 (65.5)

7.6 (1.9 to 13.3)

1.12 (1.03 to 1.21)

0.010

 All twin live births

9 (1.8)

4 (0.8)

1.0 (−0.4 to 2.4)

2.24 (0.69 to 7.23)

0.17

 Monozygotic twin live births

7 (1.4)

2 (0.4)

1.0 (−0.2 to 2.2)

3.49 (0.73 to 16.70)

0.18

Secondary outcomes

Cumulative biochemical pregnanciesd

430 (86.5)

399 (80.6)

5.9 (1.3 to 10.5)

1.07 (1.02 to 1.13)

0.01

Cumulative clinical pregnanciese

416 (83.7)

378 (76.4)

7.3 (2.4 to 12.3)

1.10 (1.03 to 1.17)

0.004

Cumulative ongoing pregnanciesf

385 (77.5)

336 (67.9)

9.6 (4.1 to 15.1)

1.14 (1.06 to 1.23)

0.00070

Cumulative pregnancy loss

 Biochemical pregnancy loss

37 (7.4)

36 (7.3)

0.2 (−3.1 to 3.4)

1.02 (0.66 to 1.59)

0.92

 Clinical pregnancy loss

54 (10.9)

54 (10.9)

−0.0 (−3.9 to 3.8)

1.00 (0.70 to 1.42)

0.98

  Miscarriage <12 weeks gestation

43 (8.7)

49 (9.9)

−1.2 (−4.9 to 2.4)

0.87 (0.59 to 1.29)

0.50

  Miscarriage 12-24 weeks gestation

11 (2.2)

5 (1.0)

1.2 (−0.4 to 2.8)

2.19 (0.77 to 6.26)

0.13

Ectopic pregnancy

7 (1.4)

11 (2.2)

−0.8 (−2.5 to 0.8)

0.63 (0.25 to 1.62)

0.34

Live birth after first embryo transferg

256/486 (52.7)

200/491 (40.7)

11.9 (5.7 to 18.2)

1.29 (1.13 to 1.48)

0.00018

Live birth after second embryo transfer

89/189 (47.1)

85/261 (32.6)

14.5 (5.4 to 23.6)

1.45 (1.15 to 1.82)

0.002

Live birth after third embryo transfer

21/52 (40.4)

36/123 (29.3)

11.1 (−4.5 to 26.7)

1.38 (0.90 to 2.12)

0.15

Live birth after natural conception

6 (1.2)

7 (1.4)

−0.2 (−1.6 to 1.2)

0.85 (0.29 to 2.52)

0.78

Median time to livebirth since randomization, daysh

344 (334−353)i

373 (353 − 416)i

−31.3 (−32.2 to −30.4)

1.26 (1.09 to 1.47)j

0.002k

No. of unused frozen embryos, mean (SD)

4.1 (3.3)

5.9 (4.0)

−1.8 (−2.3 to −1.3)

-

3.37e-14

No. of unused frozen embryos in women with a live birth, mean (SD)

4.7 (3.3)

6.4 (3.8)

−1.7 (−2.2 to −1.2)

-

7.15e-10

No. of unused frozen embryos in women without a live birth, mean (SD)

2.2 (2.6)

4.9 (4.2)

−2.7 (−3.4 to −1.9)

-

2.03e-09

No. of women without a frozen embryo

71 (14.3)

23 (4.6)

9.6 (6.0 to 13.2)

3.07 (1.95 to 4.84)

2.18e-07

 No. of women without a frozen embryo without a livebirth

46 (9.3)

22 (4.4)

4.8 (1.7 to 7.9)

2.08 (1.27 to 3.41)

0.003

 No. of women without a frozen embryo with a livebirth

25 (5.0)

1 (0.2)

4.8 (2.9 to 6.8)

24.90 (3.39 to183.05)

1.94e-06

  1. SD standard deviation.
  2. aAbsolute differences in percentages are indicated in percentage points, and absolute differences in other values are indicated in units of that value.
  3. bAll P values are for superiority, two-sided. No adjustments were made for multiple comparison. Two-sample t-test was used for continuous variable; Chi-square test was used for categorical data.
  4. cCumulative live births were calculated from up to the first 3 embryo transfers in 1 year after randomization (with a 3-months extension for those affected by Covid-19) from one oocyte retrieval cycle. Live birth was defined as delivery of any neonate ≥24 weeks gestation that had a heartbeat and was breathing. P = 5.60e-11 for non-inferiority (with margin = −0.1, α = 0.025, one-sided).
  5. dBiochemical pregnancy was defined as serum human chorionic gonadotropin ≥25 IU/L 14 days after embryo transfer.
  6. eClinical pregnancy was defined as detection of intrauterine gestation sacs at 30–35 days after embryo transfer. One woman in the cleavage-stage group was lost to follow-up after confirmation of clinical pregnancy.
  7. fOngoing pregnancy was defined as detection of a viable fetus with heartbeat at 12 weeks’ gestation. One woman in the cleavage-stage group was lost to follow-up after confirmation of an ongoing pregnancy.
  8. gLivebirth after the first embryo transfers included 235 livebirths from 536 fresh embryo transfer and 221 livebirths from 441 first frozen embryo transfer (freeze-only strategy).
  9. hThe length of time from randomization to 50% of the participants who achieved a livebirth.
  10. i95% confidence interval for median time to live birth.
  11. jHazard ratio (95% confidence interval).
  12. klog-rank test.
Back to article page