By Neus Ferrando Gilabert BSc, MSc (embryologist).
Last Update: 05/07/2014

Oocyte insemination is the 3rd step within the conventional in vitro fertilisation process.

Following egg retrieval via follicular puncture, both the female’s eggs and the male’s sperm are cultured together in a sterile dish to enable the sperm to fertilise an egg. Since oocytes are surrounded by granulosa cells, the sperm may have to pass through them.


The culture plate is placed in the incubator to the same temperature as the mother’s womb (approximately 37ºC).

Within 16-19 hours later, the granulosa cells surrounding each fertilised egg are removed.

Fertilised egg

The oocyte is observed under the microscope to determine whether it has been fertilised. Fertilised eggs have two pronuclei containing the maternal as well as the paternal genetic information.

The couple is reported whether the eggs have been properly fertilised or not. Sometimes it may also occur that, the day in which insemination has been performed (day 1), some eggs have not been fertilised, some have not engaged in a dialog with the sperm (and, thus, only have one pronucleus), or eggs with more than two pronuclei within their cytoplasm, which have no potential for life.

Authors and contributors

 Neus Ferrando Gilabert
BSc, MSc
Bachelor's Degree in Biology from the University of Valencia (UV). Postgraduate Course in Biotechnology of Human Assisted Reproduction from the Miguel Hernández University of Elche (UMH). Experience managing Embryology and Andrology Labs at Centro Médico Manzanera (Logroño, Spain). More information