Embryos Culture / Blastocyst Culture


The embryos are examined 48 hrs after egg retrieval. At this stage, best embryo contains 4 to 6 cells (blastomere). If there is timely division starting from the egg retrieval till the embryo transfer, pregnancy rates are higher. Embryo transfer can be done 56 hours to 90 hours. The timing of embryo transfer will be decided by the doctors depending upon the patient’s and embryos. 3 to 4 nos (56-72 hours) of best morphologically seen embryos are chosen for embryo transfer. If it is a blastocyst stage one to two embryos are transferred. Transforming more than 4 embryos is associated with risk of multiple pregnancy.

4 Cell – 48 hrs

8 Cell – 72 hrs

4 Cell – 48 hrs



Co-culture Technique :

Embryos are cultured along with other supporting cells example, corona cumulus cells of egg, endometrium or tissue of animal origin. This is called Co-culture. Co-cultures (feeder layers) enhances the culture medium by releasing or absorbing 10 components into or from it. These components have not been identified but might include metabolites or substrates that are important for embryonic development. Various papers have been published on this technique claiming better quality of embryos and higher implantation rates.

Blastocyst Culture

Blastocyst :-

Blastocyst is an embryo that has developed for five days after fertilization.

Most of Embryo transfers are performed on day 2 or day 3. Recently, improvement in embryo culture condition have allowed sustained embryo development to the blastocyst stage. It is stage at which embryo naturally arrives to the uterine cavity and implantation occurs. Preliminary studies with new media and age in good responder woman have shown that ~50% of the fertilized eggs reach blastocyst stage.

Disadvantages of Blastocyst culture :
  • Longer time interval between retrieval and transfer
  • No embryos or fewer embryos for freezing
  • Risk of embryo arrest
Candidate for blastocyst transfer :
  • Woman with atleast six number of good quality embryos on day II after oocyte pick up
  • Woman under age 35
  • Oocyte recipients who receives young oocytes from donor