Table 4.
Logistic models of LGA and SGA risks by birth order (AOR, 95% CI)
| Independent variable/reference level | Effect | LGA in 1st birth | LGA in 2nd birth when 1st birth was not LGA | SGA in 1st birth | SGA in 2nd birth when 1st birth was not SGA |
|---|---|---|---|---|---|
| Embryo state at the 1st birth / Fresh | Frozen | 1.74 (1.45, 2.08)*** | N/A | 0.50 (0.37, 0.67)*** | N/A |
| Embryo states at the 1st/2nd birth | P value | N/A | *** | N/A | * |
| Fresh/fresh | Fresh/frozen | 1.70 (1.46, 1.98)*** | 0.65 (0.47, 0.89)** | ||
| Frozen/fresh | 0.88 (0.58, 1.35)* | 1.39 (0.77, 2.51) | |||
| Frozen/frozen | 1.40 (1.11, 1.78) | 0.80 (0.50, 1.30) | |||
| Embryo stage / non-blastocyst | Blastocyst | – | – | 0.80 (0.68, 0.94)** | – |
| Fetal heart beats on US at the 1st birth / 1 | ≥2 | 0.70 (0.52, 0.96) * | – | 1.79 (1.39, 2.31)*** | – |
| Fetal heart beats on US at the 2nd birth / 1 | ≥2 | – | 0.73 (0.54,0.98)* | – | 1.82 (1.17, 2.82)** |
| Infant gender / Male | Female | 0.85 (0.74, 0.99) * | – | – | – |
| Parity at the 1st birth / 0 | ≥1 | 1.30 (1.04, 1.62)* | – | 0.64 (0.47, 0.89)** | – |
| Maternal BMI | P value | *** | *** | ||
| Compared to 18.5–24.9 | 14.0–18.4 | 0.60 (0.26, 1.37)** | 0.88 (0.49, 1.60) | – | – |
| 25.0–29.9 | 1.91 (1.49, 2.44) | 1.66 (1.32, 2.08) | – | – | |
| 30.0–34.9 | 2.62 (1.90, 3.63)** | 2.27 (1.66, 3.11)** | – | – | |
| 35.0–39.9 | 2.44 (1.52, 3.93) | 2.11 (1.32, 3.35) | – | – | |
| ≥40.0 | 4.48 (2.33, 8.60)*** | 1.76 (0.76, 4.05) | – | – |
N/A not applicable, – non-significant (age and prior ART cycles were non-significant for all the models)
*P < 0.05; **P < 0.01; ***P < 0.001 versus reference level. P value is a test comparing all the categories when more than two categories