Fetal DevelopmentLesson 4-9

Let’s view a baby’s growth from conception to birth. Take a

peek inside the womb to see how a baby develops from

month to month.

FERTILIZATION/CONCEPTION

• Fertilization happens when a sperm meets and penetrates an egg. • It’s also called conception.

• At this moment, the genetic makeup is complete, including the baby’s sex, coloring, and facial features.

• Within about three days after conception, the fertilized egg, called a zygote, is dividing very fast into many cells.

• It passes through the fallopian tube into the uterus, where it attaches to the uterine wall. • This is called implantation.

• The placenta, which will nourish the baby, also starts to form.

4 WEEKS

• The zygote becomes an embryo between 3-8 weeks.

• The embryo is inside a thin, fluid-filled membrane called the amniotic sac, which surrounds and protects it.

• At this point the baby is developing the structures that will eventually form his/her face and neck.

• The heart and blood vessels continue to develop, and the lungs, stomach, and liver start to develop.

• A home pregnancy test would show positive.

8 WEEKS

• The embryo is now a little over half an inch in size.

• Eyelids and ears are forming, and you can see the tip of the nose.

• The arms and legs are well formed. The fingers and toes grow longer and more distinct.

• Notice the umbilical cord, a rope-like structure that connects the embryo and the mother’s placenta.

12 WEEKS

• Sometime between 9-14 weeks the embryo becomes a fetus.

• The fetus measures about 2 inches and starts to make its own movements.

• The doctor may hear the baby’s heartbeat with special instruments.

• The sex organs of the baby should start to become clear.

16 WEEKS

• The fetus now measures about just over 4 inches and weighs about 3.5 ounces.

• The baby’s eyes can blink, it develops eyebrows and eyelashes.

• The heart and blood vessels are fully formed.

• The baby’s fingers and toes have fingerprints.

20 WEEKS

• The baby weighs about 10 ounces and is a little more than 6 inches long.

• The baby can suck a thumb, yawn, stretch, and make faces.

• The mother may already feel the baby moving, which is called “quickening.”

TIME FOR AN ULTRASOUND

• An ultrasound is usually done at 20 weeks.

• During this ultrasound the doctor will make sure that the placenta is healthy and attached normally and that the baby is growing properly.

• You can see the baby’s heartbeat and movement of its body, arms, and legs on the ultrasound.

• You can usually find out if it’s a boy or a girl at 20 weeks.

24 WEEKS

• The baby weighs about 1.4 pounds now and responds to sounds, like music and conversations, by moving or increasing his/her pulse.

• The mother may feel jerking motions if the baby hiccups. With the inner ear fully developed, the baby may be able to sense being upside down in the womb.

• The baby probably also has a scheduled sleeping pattern.

28 WEEKS

• The baby weighs about 2 pounds 6 ounces, and changes position often at this point.

• If the mother delivered prematurely now, there is a good chance (90 %) that the baby would survive.

32 WEEKS

• The baby weighs about 4 pounds and is moving around often.

• The baby’s skin has fewer wrinkles as a layer of fat starts to form under the skin.

• Between now and delivery, the baby will gain up to half his/her birth weight.

• Sometime between 29-40 weeks, the baby can use all 5 senses and has dreams.

• Most women go to the doctor every two weeks at this stage of pregnancy.

36 WEEKS

• Fetuses differ in size depending on many factors such as gender, the number of babies being carried, and the size of the parents.

• On average, a baby at this stage is about 18.5 inches and weighs close to 6 pounds.

• The brain has been developing rapidly.

• Lungs are nearly fully developed.

• The head is usually positioned down into the pelvis by now.

• A pregnancy is considered “at term” once it’s past 37 weeks.

BIRTH

• A mother’s due date marks the end of her 40th week.

• The delivery date is calculated using the first day of her last period.

• Based on this, pregnancy can last between 38 and 42 weeks with a full-term delivery happening around 40 weeks.

• GENETICS: HEREDITY, passing traits from parent to offspring.

• Genes contain instructions that help determine a certain characteristic of an individual.

• DNA the genetic information that makes up chromosomes, tiny threadlike structures that carry heredity information from generation to generation

• Chromosomes are divided into smaller units called genes.

• Every cell contains 46 chromosomes, 23 from the mother and 23 from the father

• TRAIT a characteristic that an organism can pass to its offspring through its genes

Exit Ticket

•Socrative.com, Room:DSKA8Y5MF

•COMPLETE THE FETAL DEVELOPMENT QUIZ