What are the Stages of Prenatal Development?

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  • Written By: Anna T.
  • Edited By: Melissa Wiley
  • Last Modified Date: 28 October 2019
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There are three stages of prenatal development: the conception stage, the embryonic stage, and the fetal stage. Each stage of prenatal development is carried out over the course of approximately 40 weeks, which is the average length of most pregnancies. The conception stage is the shortest, and the fetal stage is the longest. It is a good idea for a mother to be aware of exactly what occurs during each stage of development so that she can have a better understanding of what is going on with her baby and her body.

The conception stage only lasts for about two weeks, and during this time the sperm finds its way to the egg and implants itself inside. After implantation, the egg travels through the fallopian tubes into the uterus. It can take the egg an entire week to get to the uterus and implant itself inside. At this stage, the egg is referred to as a zygote, and cell division has already begun. Cell division continues until the zygote becomes a blastocyst, which is already made up of the primitive basic components that form a human body.


Once the blastocyst attaches itself to the uterine wall, it becomes known as an embryo, and the embryonic stage of prenatal development begins. At this stage of development, the embryo begins to look like something that resembles a baby as the cells continue to divide. The embryonic stage typically lasts until a woman is 11 weeks pregnant. By the end of the embryonic stage, the embryo will have arms, legs, and a heartbeat. It is at this stage of prenatal development that most women go for their first ultrasound, which helps a doctor to determine that the baby is developing normally.

At the end of 11 weeks, the embryo becomes known as a fetus, and the fetal stage begins. Most women associate the fetal stage with the beginning of the second trimester, which occurs at the end of the third month of pregnancy. During this time, a baby's sex and other major body organs start to form, and the fetus may have hair, teeth, and even small fingernails and toenails before the end of this stage. This is the stage of pregnancy when most women feel their babies kick for the first time, and the sex can typically be determined with an ultrasound at around 20 weeks. By the end of the fetal stage, at roughly 40 weeks, the fetus will normally be fully developed and ready for delivery.


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Post 3

@fify-- I believe the threshold for that is 28 weeks (7 months). The lungs might still be developing but the baby can be kept in an incubator for several weeks after birth if that's the case. When the birth is at 25 weeks or before though, it starts to get dangerous. I had read somewhere that only half of the babies born at 24 weeks survive. So even one week can make a huge difference with the baby's development.

If the baby is born anytime after 28 weeks, it will be just fine.

Post 2

What happens if there is a premature birth and the baby hasn't completed it's development? At how many weeks, will the baby be okay outside of the mom's womb?

Post 1

I can't believe that an embryo has a heartbeat at just four weeks old and eyes start to form at five weeks. It's just amazing to me how quickly it develops. They say that at nine weeks, the fetus has already developed every single organ in the body. And it does all of this on its own which is just fascinating.

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