Table 1.
Baseline characteristics of the study population, comprising women with four or more embryos available during IVF treatment. Values are number (percentage) unless stated otherwise
| Characteristics | Blastocyst stage group (n=603) | Cleavage stage group (n=599) |
|---|---|---|
| Mean (SD) age (years) | 33.9 (4.2) | 34.1 (4.2) |
| Mean (SD) BMI | 24.2 (4.4) | 24.5 (4.5) |
| Smoker | 44 (7.4) | 45 (7.6) |
| Pregnancy history: | ||
| Primary subfertility | 308 (51.2) | 333 (55.6) |
| Previous live birth | 203 (33.7) | 182 (30.4) |
| Reason for IVF or ICSI: | ||
| Male factor | 259 (43.0) | 232 (38.7) |
| Female factor | 112 (18.6) | 137 (22.9) |
| Male and female factor | 37 (6.1) | 39 (6.5) |
| Unexplained | 175 (29.1) | 155 (25.9) |
| Other | 19 (3.2) | 36 (6.0) |
| Duration of infertility (months) | 33.6 (22.3) | 33.4 (22.5) |
| Type of protocol: | ||
| GnRH antagonist | 190 (31.8) | 175 (29.3) |
| GnRH agonist | 407 (68.2) | 422 (70.7) |
| Fertilisation method: | ||
| IVF | 279 (46.3) | 271 (45.2) |
| ICSI | 316 (52.5) | 315 (52.6) |
| IVF and ICSI | 7 (1.2) | 13 (2.2) |
| No of oocyte retrievals*: | ||
| 1 | 441 (73.6) | 432 (72.4) |
| 2 | 112 (18.7) | 118 (19.8) |
| 3 | 46 (7.7) | 47 (7.9) |
| No of aspirated oocytes | 11.45 (4.9) | 11.52 (5.2) |
| Mean (SD) No of embryos on day 2 after oocyte retrieval | 7.5 (3.2) | 7.6 (3.6) |
| Type of transfer: | ||
| Fresh SET | 497 (82.4) | 494 (82.5) |
| Fresh DET | 54 (9.0) | 52 (8.8) |
| Frozen-thawed SET | 633 | 828 |
| Frozen-thawed DET | 13 | 51 |
| Fresh embryo | 52 (8.6) | 53 (8.8) |
| Risk of OHSS | 48 (8.0) | 46 (7.7) |
| Illness | 0 | 2 (0.3) |
| Technical problems | 1 (0.6) | 0 |
| Poor embryo development | 0 | 0 |
| Other reasons | 3 (0.5) | 5 (0.8) |
| Method of cryopreservation†: | ||
| Slow freeze | 2 (0.3) | 51 (8.5) |
| Vitrification | 511 (84.7) | 505 (84.3) |
BMI=body mass index; DET=double embryo transfer; GnRH=gonadotrophin releasing hormone; ICSI=intracytoplasmic sperm injection; IVF=in vitro fertilisation; OHSS=ovarian hyperstimulation syndrome; SD=standard deviation; SET=single embryo transfer.
*
Women could participate in their first, second, or third IVF or ICSI oocyte retrieval cycle, but they could only participate in one treatment cycle.
†
When possible.