7 Stages in Fetal Development

A fetus passes through seven stages of development during the 42 weeks of a pregnancy. During those 42 weeks, the mother experiences the development, too, as her body changes. Many permanent features form during the first two weeks of the baby's development after conception. Maintaining good nutrition and health by the mother influences the baby's development.

A human baby develops during 42 weeks in its mother's womb. (Image: manifeesto/iStock/Getty Images)

Zygote

After conception, when sperm fertilizes the egg, the baby's formation starts as a singular cell called a zygote. The zygote is microscopic and contains the entire DNA blueprint information regarding the cellular makeup of the child. This is the first stage of fetal development, MedlinePlus reports.

Cellular Division

The next stage in fetal development has the name of the blastocyst. The tiny zygote begins to divide again and again, forming new structures and a protective membrane to cover itself. At day six, the blastocyst enters the womb of the mother and implants itself, beginning another stage of development of the baby.

Embryo

After the blastocyst has implanted itself within the womb, new cellular divisions occur. The womb works to nourish the small baby, now called the embryo. The embryo continues to divide into its distinguishable external features. The first trimester stage is called development of the embryo, MedlinePlus reports.

The Gestational Period

The gestational period occurs between two to eight weeks after conception, during which time continued development of major organs occurs within the baby. The baby's features become defined and recognizable. Eyelids form as well as the tiny spinal column. The hands and feet develop fingers and toes. Specific facial features form during this stage, as do the intestines, meaning the digestive system begins to take form.

The Embryonic Period

This stage occurs at the end of the week eight of the gestational period. The baby has the ability to make a fist and its eyes remain closed now until the opening after the 28th week of development, MedlinePlus reports. The bones of the baby become harder during this stage. The baby starts to move around within the womb and can hear during this stage. At this point, the embryonic stage begins the second trimester.

The Second trimester

During the 26th week, the beginning of the second stage of the trimester occurs, MedlinePlus indicates. The baby continues to develop and the mother notices a change in her appearance. The baby begins to become much larger and causes the mother's abdomen to become distended. A doctor can, at this point, hear the baby's heartbeat with a stethoscope. The mother also can feel the baby kick inside her womb. The baby becomes active during this stage of development, MedlinePlus states.

The Third Trimester

The baby has the ability to open its eyes in the 28th week of development, MedlinePlus reports. This begins the last trimester of the baby's development in the womb. The baby's developmental age is now well over six months. The baby continues to grow throughout the 42 weeks, developing the final distinguishable features from its individual DNA makeup. The baby's major systems form and continue to become ready for entry into the world.

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