OBJECTIVETo explore the effects of fertilization methods and sperm sources in intracytoplasmic sperm injection (ICSI) on the developmental capacity of surplus embryos.

METHODSWe analyzed the blastocyst formation of the surplus embryos from 2 135 patients, who were divided according to fertilization methods into an IVF (n=1803) and an ICSI group (n=332), the former again allocated to a normal fertilization (n=1642) and a rescue fertilization group (n=161), and the latter, according to sperm sources, to an ejaculated (n=248), an epididymal (n=70) and a testicular sperm group (n=14). The rates of blastocyst formation and good-quality blastocysts were compared between different fertilization methods and sperm sources.

RESULTSA total of 1884 blastocysts (28.87%) formed from 6525 surplus embryos of the patients after sequential culture, of which 974 (51.70%) were good-quality ones. The blastocyst formation rate of surplus embryos was significantly higher in the IVF (30.14%) than in the ICSI group (21.40%, P < 0.05), the rate of good-quality blastocysts was also higher in the former (52.44%) than in the latter (45.54%), but with no significant difference (P > 0.05). The rates of blastocyst formation and good-quality blastocysts were significantly higher in the normal (31.04% and 53.28%) than in the rescue fertilization IVF group (20.38% and 38.54%, P < 0.05), and in the testicular sperm ICSI group (30.23% and 53.85%) than in either the epididymal (18.36% and 42.11%) or the ejaculated sperm ICSI group (21.76% and 45.70%) (P < 0.05).

CONCLUSIONThe development potential of surplus embryos was higher in IVF than in ICSI, in the normal than in the rescue fertilization IVF group, and in the testicular than in the epididymal and ejaculated sperm ICSI groups.