Table 4.
Multinomial logistic regression analysis with SSR in twins from twin gestation
| Birth* | Variables | OR | 95% CI |
|---|---|---|---|
| Female twins | Dosage of Gn (× 103 IU/L) | 0.931 | 0.805–1.076 |
| Days of Gn use (day) | 1.021 | 0.977–1.067 | |
| Age difference | |||
| Older mother | 0.815 | 0.546–1.215 | |
| Older father | 0.864 | 0.629–1.187 | |
| None | 1.000 | ||
| Embryo transfer stage | |||
| Cleavage stage | 0.783 | 0.530–1.158 | |
| Blastocyst | 1.000 | ||
| Paternal age group (year) | |||
| ≤30 | 1.056 | 0.773–1.444 | |
| 31–32 | 0.988 | 0.712–1.371 | |
| 33–35 | 1.072 | 0.794–1.448 | |
| ≥36 | 1.000 | ||
| Maternal BMI | |||
| <18.5 | 1.129 | 0.770–1.654 | |
| 18.5–23.9 | 1.048 | 0.786–1.396 | |
| ≥24 | 1.000 | ||
| Fertilization method | |||
| IVF | 1.061 | 0.703–1.600 | |
| ICSI | 0.844 | 0.514–1.386 | |
| FET | 1.000 | ||
| Boy-girl twins | Dosage of Gn (× 103 IU/L) | 0.837 | 0.715–0.980 |
| Days of Gn use (day) | 1.032 | 0.985–1.081 | |
| Age difference | |||
| Older mother | 0.917 | 0.616–1.366 | |
| Older father | 0.682 | 0.492–0.945 | |
| None | 1.000 | ||
| Embryo transfer stage | |||
| Cleavage stage | 1.754 | 1.133–2.716 | |
| Blastocyst | 1.000 | ||
| Paternal age group (year) | |||
| ≤30 | 0.939 | 0.672–1.312 | |
| 31–32 | 0.972 | 0.686–1.377 | |
| 33–35 | 0.995 | 0.719–1.377 | |
| ≥36 | 1.000 | ||
| Maternal BMI | |||
| <18.5 | 1.340 | 0.892–2.012 | |
| 18.5–23.9 | 1.160 | 0.845–1.591 | |
| ≥24 | 1.000 | ||
| Fertilization method | |||
| IVF | 0.846 | 0.546–1.312 | |
| ICSI | 0.882 | 0.531–1.464 | |
| FET | 1.000 |
*Male twins selected as the reference category
SSR Secondary sex ratio, IVF In vitro fertilization, ICSI Intracytoplasmic sperm injection, FET Frozen embryo transfer, Gn Gonadotropin, BMI Body mass index