Table I.
Baseline and stimulation characteristics of day 5 (n = 4120) and day 6 (n = 230) transfer cohorts.
| Variable | Day 5 | Day 6 | P value |
|---|---|---|---|
| Age (years) | 34 (31–38) | 36 (32–38.5) | 0.01 |
| BMI (kg/m2) | 25 (22–29) | 24 (22–28) | 0.06 |
| Gonadotrophins (IU) | 3300 (2325–5100) | 3900 (2700–6075) | <0.001 |
| Estradiol on day of trigger (pg/ml) | 2457 (1803–3217) | 2439 (1795–3201) | 0.53 |
| Progesterone on day of trigger (ng/ml) | 1.0 (0.7–1.3) | 1.1 (0.8–1.5) | 0.01 |
| Oocytes retrieved | 14 (10–19) | 14 (10–19) | 0.64 |
| Vitrified embryos | 1 (0–4) | 1 (1–2) | <0.001 |
| Blastocyst transfer | 91.6% | 90.8% | 0.92 |
| Good quality embryo transfer | 83.3% | 73.0% | <0.001 |
| Number of embryos transferred | 1 (1–2) | 1 (1–2) | 0.02 |
| Live birth (≥24 weeks gestation) | 45.6% | 34.0% | 0.01 |
Data expressed as median (interquartile range) or percentage of outcome. Statistical comparisons derived from generalized estimating equations (GEE) models.