Please contact us at: 732-758-6511

Blastocyst Culture

Blastocyst Culture and Development

Once an embryo is created it can be left in the laboratory to culture for up to six days. Some patients are good candidates for extended culture or Day 5 culture based on the following guidelines:

  • Number of embryos growing in the lab is more than five.
  • Overall high quality embryos.
  • Day three development shows embryos growing with 6 – 8 cells.
  • Day three development shows embryos with low fragmentation and good cell symmetry (Grade 1-2 embryos).
  • Patient is concerned about getting pregnant with twins or triplets.
  • You can put back less embryos and still have a high chance of becoming pregnant.
  • Patient does not want to freeze extra embryos.
  • Patient is using PGS with their IVF cycle.
All patients are counseled on the option of having blastocyst culture with their IVF cycle. A final decision – except in the case of using PGS – cannot be made until day two or three of embryo development. The staff will keep you informed of the embryos’ progress and a recommendation will be made at the appropriate time.

It is not considered a “failed cycle” if embryos are not grown to day 5 of development. Some patients have between two and four high quality embryos on day 3 and there is no need to keep them in the laboratory any longer. Also, it may be beneficial to some patients to have Assisted Hatching done on their embryos. For the safety of the embryos, this procedure is performed on day 3 of development just before the embryos are placed back in the patient.

The photographs above are embryos at day 3 and day 5 of development.

  • Day 3 embryos are generally between 5-8 cells.
  • Day 5 embryos have over 100 cells and have begun to differentiate into different cell structures.
  • Inner Cell Mass – Cluster of cells that develops into the baby – this is where embryonic stem cells come from.
  • Trophectoderm – outer cells of Blastocyst, with the appearance of a soccer ball – these cells become the placenta that will support the baby during pregnancy.
  • Zona Pellucida – The shell of the embryo – this thins out as the days progress further toward implantation which occurs on day 6 or 7 of development. You can see the difference in the thickness of the zona pellucida between the embryos in these two pictures.

Stages of Blastocyst Development

There are five general stages that we use to describe the progress of a day 5 embryo:


The cells from the day 3 embryo become compacted and loose their individual appearance. There is no change in the thickness of the zona pellucida.

Early Blastocyst

At this next stage of development the blastomeres or cells start to pinch off and a cavity develops. Inside the cavity the inner cell mass will form. The outside cell layer is the trophectoderm. The zona pellucida has had little to no change in thickness. At this stage it is still difficult to tell the quality of the inner cell mass. Blastocyst embryos at this stage are too early to freeze for later use.

Full Blastocyst

The cavity of the blastocyst has expanded and the inner cell mass is more visible. The zona pellucida is visible thinning. We recommend freezing blastocyst embryos with a good inner cell mass and trophectoderm at this point.

Expanded Blastocyst

The cavity is clearly expanded, the inner cell mass clearly defined and the zona pellucida has become so thin it is hardly visible. This stage of blastocyst embryo are also suitable for freezing.

Hatching Blastocyst

This is the final stage of development before implantation. The blastocyst has expanded beyond the capacity of the zona pellucida. This expansion has caused the shell to tear. The blastocyst slowly exits and leaves this shell behind. It is believed at this point Assisted Hatching may demonstrate its benefits. By placing an opening in the shell a few days prior, the blastocyst already will have its exit when it reaches this point of development. Patients with shells that prove too difficult or impossible to tear may prohibit an otherwise healthy blastocyst from leaving the shell and implanting into the uterus.


Damien Fertility Partners
655 Shrewsbury Avenue
Shrewsbury, NJ 07702
Phone: 732-758-6511
Fax: 732-758-1048


Damien Fertility Partners
60 Park Place, Suite 210
Newark, NJ 07102
Phone: 973-732-2909
Fax: 732-758-1048

Jersey City

Damien Fertility Partners
138 River Drive South
Jersey City, NJ 07310
Phone: 201-377-0500
Fax: 732-758-1048