Surrogacy and the medical terms involved can feel overwhelming. That's why we're here to help simplify every concept you need to understand.
One term that often confuses is "zygote," especially when discussing early pregnancy or IVF. Simply put, a zygote is the very first stage of human development after fertilization, but it is not yet an embryo. Understanding this crucial difference can bring clarity to the earliest phases of life.
Whether you're looking to understand more about embryos, fetuses or zygotes, we offer free information to help guide you. And if you're considering surrogacy, we can begin matching you with a potential surrogate mother once you fill out our online contact form.
What Is a Zygote
A zygote is the single-cell stage of human development that occurs when an egg and sperm unite. It contains 23 chromosomes from each parent and lasts about four days before progressing to the next phase.
Embryo vs. Zygote: Understanding the Key Differences
The zygote is the first single-cell stage, while the embryo is the next developmental phase after the zygote undergoes several cell divisions.
Once the zygote reaches the blastocyst stage (around 5-6 days post-fertilization), it is called an embryo.
During IVF, a blastocyst is the stage of development that is typically transferred into the uterus for the best chance of implantation.
The blastocyst will eventually develop into both the embryo and the placenta.
The key difference: a zygote becomes an embryo after a series of developmental stages.
Here’s a quick overview of those stages:
The zygote undergoes rapid cell division, becoming a cluster of cells known as a morula. These divisions increase cell numbers without the zygote growing in size. By now, the zygote has divided into 16 or more cells, forming a solid ball. Cells begin to specialize during this stage. At this stage, the zygote transforms into a blastocyst, a hollow ball of cells. The inner cells will develop into the embryo, while the outer cells help form the placenta. This stage is crucial for embryo transfer and successful implantation in the uterus. Now preparing for implantation, the blastocyst attaches to the uterine lining, officially marking the transition to the embryonic stage. Once the blastocyst embeds into the uterus, it becomes an embryo, beginning the formation of the placenta and amniotic sac. This stage also marks the start of the development of vital organs like the brain, heart, and spinal cord.
Is a Zygote Just a Fertilized Egg?
Yes, a zygote is essentially a fertilized egg. Within 24 hours of fertilization, the egg and sperm form a single cell, marking the official start of pregnancy.
If you'd like more detailed information about zygotes, embryos, or fetuses, we're here to provide that for free. If you're considering surrogacy, feel free to reach out to us online to start the matching process with a prospective surrogate mother today.