Table 2.
Outcome of pregnancy by embryo-state groups
| (N, pairs) | Birth | Embryo state in 1st and 2nd pregnancies | |||
|---|---|---|---|---|---|
| Order | Fresh/fresh | Fresh/frozen | Frozen/fresh | Frozen/frozen | |
| (3241) | (3371) | (310) | (873) | ||
| Single fetal heartbeat at 6-week ultrasound (%) |
1 | 92.0 | 91.2 | 95.1 | 93.1 |
| 2 | 90.8 | 94.9 | 87.1 | 95.3 | |
| Infant gender (% female)a | 1, 2 | 49.0 | 48.1 | 46.4 | 50.7 |
| Length of gestation (days, SD) | 1 | 268.9 (14.7) | 267.7 (15.9) | 269.0 (14.7) | 268.3 (16.3) |
| 2 | 267.3 (12.6) | 267.3 (13.1) | 266.2 (15.7) | 266.4 (14.4) | |
| Difference (days, SE) | –1.6 (0.3) | –0.3 (0.3) | –2.9 (1.1) | –2.0 (0.6) | |
| P value | *** | NS | ** | *** | |
| Birthweight (g, SD) | 1 | 3257 (574) | 3246 (600) | 3376 (588) | 3390 (609) |
| 2 | 3338 (548) | 3468 (569) | 3295 (618) | 3418 (615) | |
| Difference (g, SE) | +81 (11) | +222 (11) | –81 (37) | +28 (23) | |
| P value | *** | *** | * | NS | |
| Birthweight z-score (SD, SD) | 1 | 0.00 (1.02) | 0.04 (1.02) | 0.25 (1.11) | 0.34 (0.99) |
| 2 | 0.26 (1.02) | 0.55 (1.06) | 0.24 (1.00) | 0.50 (1.01) | |
| Difference (Z, SE) | 0.26 (0.02) | 0.51 (0.02) | 0.00 (0.06) | 0.16 (0.03) | |
| P value | *** | *** | NS | *** | |
| LGA birthweight % | 1 | 9.8 | 9.2 | 13.1 | 15.8 |
| 2 | 14.2 | 20.8 | 15.4 | 21.0 | |
| LGA birthweight in the 2nd birth | |||||
| When the 1st birth was not LGA % | 2 | 11.0 | 17.5 | 9.4 | 15.2 |
| SGA birthweight % | 1 | 8.8 | 8.0 | 5.6 | 3.5 |
| 2 | 4.5 | 2.8 | 5.6 | 3.3 | |
| SGA birthweight in the 2nd birth | |||||
| When the 1st birth was not SGA % | 2 | 3.3 | 2.1 | 4.5 | 2.6 |
NS not significant
aSiblings were matched on gender
*P < 0.05
**P < 0.01
***P < 0.001