Table 4. Pregnancy Outcomes in Double-Embryo Transfer (DET) vs Single-Embryo Transfer (SET) Pregnancies, Stratified by Fresh or Frozen Cycle and Cleavage Stage or Blastocyst Transfers.
| Fresh cycles (n = 23 982) | Frozen cycles (n = 11 854) | P valueb | Cleavage stage (n = 24 339) | Blastocyst transfers (n = 24 339) | P valueb | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| AAR, % (95% CI) | ARD, percentage points (95% CI) | RRR or OR (95% CI)a | AAR, % (95% CI) | ARD, percentage points (95% CI) | RRR or OR (95% CI)a | AAR, % (95% CI) | ARD, percentage points (95% CI) | RRR or OR (95% CI)a | AAR, % (95% CI) | ARD, percentage points (95% CI) | RRR or OR (95% CI)a | |||||||
| DET | SET | DET | SET | DET | SET | DET | SET | |||||||||||
| Gestational age (vs term) | .09 | .01 | ||||||||||||||||
| Moderately preterm | 5.4 (4.6 to 6.1) | 6.3 (6.0 to 6.7) | −1.0 (−1.8 to −0.1) | 0.84 (0.72 to 0.98) | 4.8 (3.4 to 6.2) | 4.8 (4.4 to 5.2) | 0.0 (−1.5 to 1.5) | 1.00 (0.72 to 1.38) | 5.2 (4.5 to 5.8) | 5.8 (5.5 to 6.1) | −0.6 (−1.4 to 0.1) | 0.89 (0.76 to 1.03) | 6.0 (3.9 to 8.1) | 5.8 (5.3 to 6.2) | 0.3 (−1.9 to 2.4) | 1.05 (0.72 to 1.54) | ||
| Very preterm | 1.3 (0.9 to 1.7) | 1.3 (1.2 to 1.5) | 0.0 (−0.4 to 0.4) | 0.98 (0.71 to 1.35) | 2.0 (1.0 to 2.9) | 1.0 (0.8 to 1.2) | 0.9 (−0.1 to 1.9) | 1.90 (1.11 to 3.27) | 1.3 (0.9 to 1.6) | 1.3 (1.1 to 1.4) | 0.0 (−0.4 to 0.4) | 0.98 (0.72 to 1.35) | 3.0 (1.5 to 4.5) | 1.2 (0.9 to 1.4) | 1.8 (0.3 to 3.4) | 2.64 (1.50 to 4.63) | ||
| Low birth weight (<2500 g vs ≥2500 g) | 4.6 (3.9 to 5.3) | 5.6 (5.3 to 5.9) | −1.0 (−1.7 to −0.2) | 0.82 (0.69 to 0.97) | 5.4 (3.9 to 6.9) | 3.3 (3.0 to 3.7) | 2.0 (0.5 to 3.5) | 1.64 (1.19 to 2.25) | <.001 | 4.5 (3.8 to 5.1) | 5.2 (4.8 to 5.5) | −0.7 (−1.4 to 0.0) | 0.86 (0.73 to 1.01) | 7.4 (5.1 to 9.7) | 4.2 (3.8 to 4.6) | 3.2 (0.9 to 5.5) | 1.83 (1.29 to 2.60) | <.001 |
| BWGA percentile (vs 25.0-74.9) | .45 | .58 | ||||||||||||||||
| <10.0 | 22.6 (20.8 to 24.3) | 22.7 (22.0 to 23.4) | −0.1 (−2.0 to 1.8) | 0.99 (0.89 to 1.11) | 18.8 (15.4 to 22.2) | 16.3 (15.4 to 17.3) | 2.5 (−1.0 to 6.0) | 1.19 (0.94 to 1.50) | 21.9 (20.3 to 23.6) | 21.8 (21.1 to 22.5) | 0.1 (−1.7 to 1.9) | 1.01 (0.90 to 1.12) | 20.7 (16.1 to 25.3) | 18.5 (17.5 to 19.4) | 2.3 (−2.5 to 7.0) | 1.16 (0.86 to 1.55) | ||
| 10.0-24.9 | 27.9 (26.1 to 29.7) | 27.0 (26.3 to 27.8) | 0.9 (−1.1 to 2.8) | 1.04 (0.95 to 1.15) | 22.3 (18.9 to 25.8) | 22.5 (21.5 to 23.5) | −0.2 (−3.8 to 3.4) | 0.99 (0.80 to 1.22) | 27.3 (25.6 to 29.0) | 25.9 (25.1 to 26.7) | 1.4 (−0.5 to 3.2) | 1.07 (0.97 to 1.18) | 23.5 (18.8 to 28.3) | 24.9 (23.8 to 25.9) | −1.3 (−6.2 to 3.6) | 0.93 (0.71 to 1.22) | ||
| 75.0-89.9 | 17.5 (15.9 to 19.1) | 17.8 (17.1 to 18.6) | −0.4 (−2.1 to 1.4) | 0.98 (0.86 to 1.10) | 21.0 (17.7 to 24.2) | 23.1 (22.1 to 24.1) | −2.1 (−5.5 to 1.3) | 0.88 (0.72 to 1.08) | 17.8 (16.3 to 19.3) | 18.8 (18.1 to 19.5) | −0.9 (−2.6 to 0.7) | 0.94 (0.84 to 1.05) | 22.1 (17.5 to 26.7) | 21.6 (20.6 to 22.6) | 0.5 (−4.3 to 5.2) | 1.03 (0.78 to 1.36) | ||
| ≥90.0 | 10.8 (9.5 to 12.1) | 11.8 (11.1 to 12.4) | −1.0 (−2.5 to 0.5) | 0.90 (0.78 to 1.05) | 15.1 (12.2 to 18.0) | 18.1 (17.1 to 19.0) | −3.0 (−6.0 to 0.0) | 0.80 (0.63 to 1.02) | 11.4 (10.1 to 12.6) | 13.2 (12.6 to 13.8) | −1.8 (−3.3 to −0.4) | 0.84 (0.73 to 0.97) | 14.6 (10.5 to 18.6) | 15.9 (15.0 to 16.9) | −1.4 (−5.5 to 2.8) | 0.90 (0.64 to 1.26) | ||
Abbreviations: AAR, adjusted absolute risk; ARD, absolute risk difference; BWGA, birth weight for gestational age; OR, odds ratio; RRR, relative risk ratio.
a
Odds ratios for binary outcomes and RRRs for categorical outcomes.
b
P value for interaction. Likelihood ratio tests for interaction between each outcome and fresh or frozen cycle with cleavage stage embryos, or fresh or frozen cycle with blastocyst embryos. Models were adjusted for maternal age at delivery, birth order, delivery year, maternal country of birth, previous spontaneous abortion, previous extrauterine pregnancy, and total number of stimulations.