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Difference between Embryo and Fetus

Difference between Embryo and Fetus

Embryo and fetus are both human development stages, but they have different meanings. An embryo is a name for a developing baby before it becomes a fetus. A fetus is an unborn baby after eight weeks of development. The terms are often used interchangeably, but they have important distinctions. embryos can be frozen for future use, while fetuses cannot. The use of these words can be confusing to some people because in some cases the word “fetus” is used to describe something that is not actually human. For example, when referring to certain animals that are still in their early developmental stages, like chickens or pigs, we might say “fetal stage”.

What is Embryo?

An embryo is a baby in its earliest stage of development. In humans, this period begins at fertilization, when a sperm fuses with an egg to form a single cell. The next few weeks are characterized by rapid growth and cell division as the embryo grows and develops into a fetus. Although every pregnancy is unique, most babies born around 40 weeks after fertilization weigh between six and nine pounds and are between 19 and 21 inches long. Embryos that are born before they have reached full term (40 weeks) are considered premature and may require special care. Babies born after 42 weeks are considered post-mature and may also be at higher risk for complications.

What is Fetus?

A fetus is the unborn offspring of a mammal, typically developing inside the mother’s womb during pregnancy. In human beings, the fetal stage of development begins after about eight weeks from fertilization and lasts until birth. The average pregnancy lasts for about forty weeks from the woman’s last menstrual period (LMP). After twenty weeks, the fetus is considered viable, meaning that it could survive outside of the womb with medical intervention. However, most babies are born before they reach full-term – 37 to 42 weeks gestation. Fetal development is a complex process that is controlled by both genetic and environmental factors. During pregnancy, the mother and fetus must work together to ensure that the fetus receives the nutrients and oxygen it needs to grow and develop. Ultimately, the goal of fetal development is to produce a healthy baby that is ready to survive and thrive in the world outside of the womb.

Difference between Embryo and Fetus

An embryo is the earliest stage of human development, from fertilization (joining of an egg and sperm) to the end of the eighth week of pregnancy. By the end of the eighth week, all major structures have formed and the rapidly growing fetus (developing baby) is about 1/2 inch long. From the ninth week until birth, the developing baby is called a fetus. Major structures continue to develop during this time, but growth is much slower than during the embryonic stage. By the end of the third month, the fetus is about 3 inches long and weighs about an ounce. During the fourth month, bones begin to harden, and joints begin to form. The fetal skeleton continues to develop throughout pregnancy as do all other organ systems. By full-term delivery at about 40 weeks, a baby weighs about 7 to 8 pounds and is about 20 inches long. Although all babies are different, these are general averages.


The terms embryo and fetus are often used interchangeably, but they have different meanings. An embryo is the earliest stage of development in a pregnancy, while a fetus is an unborn baby who has developed beyond the embryonic stage. It’s important to understand the difference between these two stages because some research involving embryos may not be applicable to fetuses. For example, studies on stem cells derived from embryos can’t necessarily be applied to stem cells taken from fetuses.

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