Table 3.
Regression models of differences in outcomes by embryo-state groups
| Independent variable/reference level | Effect | Gestation (days) | Birthweight (g) | Birthweight z-score | |||
|---|---|---|---|---|---|---|---|
| 1st birth | 2nd birth | 1st birth | 2nd birth | 1st birth | 2nd birth | ||
| Embryo state at the 1st birth/fresh | Frozen | – | N/A | 126 (19)*** | N/A | 0.30 (0.03)*** | N/A |
| Embryo states at the 1st/2nd birth | P value | N/A | ** | N/A | *** | N/A | *** |
| Fresh/fresh | Fresh/frozen | 0.67 (0.33)* | 131 (13)*** | 0.26 (0.02)*** | |||
| Frozen/fresh | –1.10 (0.76) | –80 (31)* | –0.11 (0.06)* | ||||
| Frozen/frozen | –0.65 (0.49) | 27 (20) | 0.08 (0.04)* | ||||
| Embryo stage/non-blastocyst | Blastocyst | –2.61 (0.36)*** | –1.74 (0.31)*** | –28 (14)* | –27 (13)* | 0.06 (0.02)* | – |
| Fetal heart beats on US at the 1st birth / 1 | ≥2 | –4.93 (0.64)*** | –218 (24)*** | 55 (22)* | –0.21 (0.04)*** | 0.09 (0.04)* | |
| Fetal heart beats on US at the 2nd birth / 1 | ≥2 | N/A | –2.93(0.57)*** | N/A | –181(23)*** | N/A | –0.22 (0.04)*** |
| Infant gender / Male | Female | 1.23 (0.35)*** | 1.01 (0.29)*** | –109 (13)*** | –90 (12)*** | – | –0.07 (0.02)** |
| Parity at the 1st birth / 0 | ≥1 | –2.66 (0.57)*** | – | 58 (22)** | – | 0.22 (0.04)*** | – |
| Maternal BMI | P value | *** | *** | ** | *** | *** | *** |
| Compared to 18.5–24.9 | 14.0–18.4 | 0.39 (1.39) | 0.73 (1.16) | –134 (53)* | –56 (48) | –0.32 (0.10)*** | –0.12 (0.09) |
| 25.0–29.9 | –1.37 (0.61)* | –0.42 (0.51) | 49 (23)* | 83 (21)*** | 0.20 (0.04)*** | 0.18 (0.04)*** | |
| 30.0–34.9 | –3.74 (0.91)*** | –2.61 (0.76)*** | 65 (35) | 69 (31)* | 0.40 (0.06)*** | 0.28 (0.06)*** | |
| 35.0–39.9 | –5.13 (1.34)*** | –4.26 (1.12)*** | –58 (52) | 35 (46) | 0.21 (0.09)* | 0.28 (0.08)*** | |
| ≥40.0 | –4.97 (2.17)* | –3.89 (1.81)* | 91 (83) | 108 (74) | 0.51 (0.15)*** | 0.45 (0.13)*** | |
| Maternal age at the 1st birth | P value | ** | |||||
| Compared to 18–29 years | 30–34 years | 1.43 (0.44)** | – | – | – | – | – |
| 35–37 years | 1.99 (0.53)*** | – | – | – | – | – | |
| 38–40 years | 1.89 (0.70)** | – | – | – | – | – | |
| 41–43 years | 3.22 (1.64)* | – | – | – | – | – | |
Models at the 2nd birth also included value at the 1st birth of the factor being modeled; all tests p < 0.0001
N/A not applicable,– non-significant (prior ART cycles was non-significant for all the models)
*P < 0.05; **P < 0.01; ***P < 0.001 versus reference level. P value is test comparing all the categories when more than two categories