By Laura Garrido BSc, MSc (embryologist).
Last Update: 05/13/2014

Embryo culture at conventional in vitro fertilisation and ICSI is essential. A fertilized egg becomes an embryo. The development stage of all embryos is assessed in order to check embryo quality and determine which the best embryos are for the transfer.

The different sections of this article have been assembled into the following table of contents.

Day 2

Two days after follicular puncture or egg retrieval and oocyte insemination, embryos would have shared the genetic information from the male and the female (pronuclei) and their cleavage pattern would be in the 2-4 cell or blastomeres stage.

At this stage, the embryo is referred to as “zygote”. Once it is at the 4-cell stage, it will contain its own genes.

Day 3

Three days after oocyte fertilisation, embryos are in the 6-8 cell stage and are prepared for glucose uptake in the uterine cavity.

Day 4

Four days after fertilisation, the embryo is at morula stage and consists of roughly 16 to 32 cells.

Day 5

Five days after fertilisation, the embryo contains about 100 cells total and is at blastocyst stage.

Day 6

Six days after fertilisation, hatching occurs. Hatching is the process in which the inner cell mass (ICM) breaks through the membrane protecting it in order to become attached to the endometrium in the woman’s uterine cavity.

Day 7

Seven days after fertilisation, implantation in the maternal uterus occurs because of the interaction between the IMC and the endometrium.

Embryo culture is conducted up to the second or the third day after follicular puncture or the fifth day after the puncture. It is determined on the basis of the type of infertility problem (e.g. the need to perform a PGD), the number of oocytes, embryo development in previous in vitro fertilisation cycles, etc.

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Authors and contributors

 Laura Garrido
BSc, MSc
Embryologist
Bachelor's Degree in Biotechnology from the Pablo de Olavide University (UPO) of Seville, Spain. Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI). Experience at IVF, andrology, and general analysis laboratories. Embryologist specialized in Assisted Reproduction. More information
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