Understanding the Stages of Embryo Growth: IVF and Pregnancy Info By Sonja Kristiansen, MD on August 30, 2016

A fertility specialist fertilizing an eggHere at the Centre for Reproductive Medicine, we want to make sure that patients undergo the most effective treatment possible. This means carefully considering their situation and how treatment can be tailored to meet their needs. This patient-center approach to custom care makes us one of the leading fertility treatment practices in Lubbock.

One of the most important parts of the in vitro fertilization (IVF) process is embryo transfer. We'd like to take a moment to consider what an embryo is and why timing is crucial when it comes to embryonic development and the IVF process.

What Is an Embryo?

In the most basic of terms, an embryo refers to an egg that is unhatched in which an offspring is in the process of developing. An embryo is what happens when sperm fertilizes an egg.

Why Embryonic Development Is So Important in IVF

During in vitro fertilization (IVF), an egg is fertilized in a lab setting. Following fertilization, the embryo is allowed to develop in a lab, undergoing cellular division under strict monitoring. By paying attention to the development of the embryo, a fertility specialist can transfer it to the womb and maximize the chances of successful pregnancy and livebirth.

Here is a basic day-by-day breakdown of embryo development.

Fertilization - The Zygote

In the first day of embryonic development, the sperm fertilizes an egg, fusing the separate genetic material. This results in zygote.

Cleavage - Cells Begin to Split

Cleavage is a process in which the zygote goes from a single-cell organism to a multi-cell organism. Through a process known as mitosis, the single cell becomes two cells, and then four cells, and then eight cells.

Compaction - A Change in Shape

As the process of cellular division continues, the shape of the embryo will begin to change. Initially the embryo will be round or spherical. As the cells divide, the embryo will still be spherical, though the multiple cells will be visible. The visibility of the multiple cells is known as compaction. By day three, up to 30 cells may be visible.

Differentiation - A Change in Cells

By the forth day of embryonic development, differentiation tends to occur. This is an important part of overall cellular growth. In essence, the simple cells of the embryo will transform into more complex cells, allowing for the formation of human tissues as well as other cell types.

About Blastocysts

By the fifth or sixth day of embryonic development, a blastocyst will have formed. This is a cluster of complex cells, with up to 200 cells present. In a natural pregnancy, the blastocyst would typically implant itself along the mother's uterine lining to develop into a fetus.

Best Stage for IVF Embryo Transfer

There are different considerations when it comes to embryo transfer during IVF. For many women, the process takes place when the embryo has divided into about eight cells, so roughly day three. In other cases, a fertility specialist may wait to transfer an embryo until a blastocyst has formed. These matters can be discussed in further detail during the actual treatment process.

Schedule a Consultation with Our Fertility Specialists

For more information about fertility treatments and how we can help you start the family of your dreams, be sure to contact our team of experienced fertility specialists today. The team at the Centre for Reproductive Medicine is here to help you overcome male and female infertility issues.

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Dr. Sonja Kristiansen

Houston Fertility Center

Dr. Sonja Kristiansen is the founder and Medical Director of Houston Fertility Center. She is a board-certified Reproductive Endocrinologist Infertility (REI) specialist who is proud to help hopeful parents fulfill their dreams of having children. Our center is affiliated with the:

  • American College of Obstetricians and Gynecologists
  • American Society for Reproductive Medicine
  • Texas Medical Association

We provide convenient care for patients from greater Houston and visitors from out of town. For more information about our services, contact our office online or call (713) 225-5375 today.

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