Comparison of in-vitro development of embryos originating from either conventional in-vitro fertilization or intracytoplasmic sperm injection

In this retrospective study on 1628 consecutive cycles performed during a period of 4 years, development in vitro is compared of embryos obtained after either conventional in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). At 39-42 h after insemination or injection, embryos obtained after ICSI were significantly (P < 0.01) further developed (mean cell number 3.48 +/- 0.03) as compared with those obtained after IVF (3.22 +/- 0.03), whereas after 63-66 h of in-vitro development this difference was no longer present (mean cell number 6.11 +/- 0.15 versus 6.09 +/- 0.13 respectively). Culture of surplus embryos obtained after IVF resulted in a significantly higher (P < 0.001) mean incidence of blastocyst formation per cycle as compared with the ICSI group (31.8 +/- 1.9 versus 23.0 +/- 1.4 respectively). Blastocysts from both groups consisted of comparable numbers of cells. Blastocyst formation was also significantly higher when embryos were cultured in groups (31.2 +/- 1.8) compared to single culture (23.1 +/- 1.5; P < 0.01), in human tubal fluid (HTF) medium (29.2 +/- 1.7) compared with IVF-50(TM) medium (24.2 +/- 1.6; P < 0.01), and when they were cultured under 5% O(2) (30.3 +/- 1.5) compared with 20% O(2) (21.7 +/- 1.7; P < 0.01). In all culture conditions used, the mean incidence of blastocyst formation per cycle showed comparable differences in favour of the IVF group as compared with the ICSI group.