Fetal development begins shortly after conception. Find out how a baby grows and develops during the first trimester. you are pregnant. our end! You will undoubtedly spend the following months thinking about how your baby is growing and developing. What does the child look like? How often do you feed him? When will you feel the first kick? Normally, the fetus develops in a predictable way. Find out what
Occurs during the first trimester by checking these events weekly. Keep in mind that measurements are approximate.
Weeks 1 and 2: Get ready
It may sound strange, but the fact is that you do not consider yourself pregnant in the first or second week of your pregnancy. Yes, what you read is correct!
Pregnancy usually occurs about two weeks after the start of your last menstrual period. To calculate the time of delivery, the health care provider will calculate 40 weeks since the start of the last menstrual period. This means that the period of menstruation is counted as part of the pregnancy period - even if pregnancy did not occur at the time.
Week 3: Fertilization
The sperm and egg unite together in one of the fallopian tubes to form a one-celled organism called a zygote. If more than one egg is released and fertilized, it may result in multiple zygotes.
Normally, a zygote consists of 46 chromosomes - 23 from you and 23 from the father. These chromosomes help determine the sex of the child and its characteristics such as eye and hair color, and to some extent, personality and intelligence.
Shortly after fertilization, the zygote travels from the fallopian tube down to the uterus. At the same time, it begins to divide to form a group of cells resembling small berries - thymus.
Week 4: Implantation
Upon reaching the uterus, the dividing ball of cells rapidly separates into two to become the blastocyst.
The inner group of cells becomes the embryo. while the outer group becomes the cells that nourish and protect the embryo. Upon contact, the blastocyst burrows into the uterine wall to feed. This process is called implantation.
The placenta also begins to form and nourishes the baby throughout the pregnancy.
Week 5: The embryonic cycle begins
The fifth week of pregnancy, or the third week after conception, is marked by the beginning of the embryonic cycle. Where the child''s brain, spinal cord, heart and other organs are formed.
The embryo now consists of three layers. The upper layer - the ectoderm - which will be the outermost layer of the baby''s skin, central and peripheral nervous systems, eyes, inner ear and many connective tissues.
The development of the baby''s heart and primitive circulatory system takes place within the middle layer of cells - the mesoderm. This layer of cells also makes up the baby''s bones, muscles, kidneys, and much of the reproductive system.
The inner layer of cells - the endoderm - becomes a simple tube lined with mucous membranes. This is where the baby''s lungs, intestines and bladder develop.
By the end of this week, the baby may be about the size of a pencil tip.
Week 6: The neural tube closes
Growth is fast during this week. Immediately four weeks after conception, the neural tube that runs along the baby''s back closes and the baby''s heart begins to pump blood.
Basic facial features begin to appear, including the passages that will be the inner ear and the arches that will be the jaw. The baby''s body begins to form a C curve. Soon after, the young shoots become arms and stems.
Week 7: Baby''s head development
Seven weeks after conception, or five weeks after conception, a baby''s brain and face are growing rapidly. Small nostrils become visible, and the lenses of the eyes begin to form. The arm buds that appeared in the previous week take the form of paddles.
By the end of this week, the fetus may be slightly larger than the tip of a pencil.
Week 8: Baby''s eyes become visible
During eight weeks of pregnancy, or six weeks after conception, the baby''s arms and legs are getting longer, and fingers are beginning to form. The shell-like parts of the baby''s ear also form, and the baby''s eyes become visible. It consists of the upper lip and nose. The torso of the baby''s body begins to straighten.
By the end of this week, the baby may be about 1/2 inch (11 to 14 millimeters) long.
Week 9: Baby''s toes are formed
In the ninth week of pregnancy, or seven weeks after its occurrence, the baby''s arms are growing and the bones are growing and bending at the elbows. Toes are forming, and baby''s eyelids and ears continue to develop.
By the end of this week, the baby may be about 3/4 inch (20 millimeters) long.
Week 10: The baby''s neck begins to grow
By the tenth week of pregnancy, or eight weeks after conception, the baby''s head will become more round. The neck begins to develop, and his eyelids begin to close to protect his developing eyes.
Week 11: The baby''s reproductive organs are developing
At the beginning of the eleventh week of pregnancy, or after the ninth week of its occurrence, the baby''s head is still approximately half its length. However, the baby''s body is almost complete, as it grows rapidly in the following weeks.
The baby is then officially described as a fetus. This week, the baby''s eyes are widely separated, the eyelids are fused, and the ears are lowered. Red blood cells begin to form in the baby''s liver. By the end of this week, the baby''s external genitalia will begin to develop in the form of a penis for males or a clitoris and labia majora for females.
When the baby is 2 inches (50 millimeters) long from head to rump and weighs about 1/3 ounce (8 grams).
Week 12: Baby''s toenails are growing
By 12 weeks of pregnancy, or 10 weeks after conception, your baby''s toenails are growing in. The child''s face is now human.
When the baby is 2 1/2 inches (60 millimeters) long from head to rump and weighs about 1/2 ounce (14 grams).
