Ch. 8 Prenatal Development
Caregiving Service
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Development Before Birth
Prenatal development: the development of the fetus before birth
A full term pregnancy lasts about 9 months, or 40 weeks, or 280 days
Pregnancy is broken into three sections called trimesters (3 months each)
Three stages of development: zygote, embryo, fetus
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First Trimester (1st-3rd months)
Zygote Stage
From conception to first 2 weeks of pregnancy
A fertilized egg that travels from the fallopian tube to attach itself to the uterine wall
The cells multiply as they grow
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Embryonic Stage
Lasts from the 3rd-8th week of pregnancy
Three layers of cells:
o Ectoderm- outer layer: skin, hair, nails, nervous system, brain, spinal cord, & nerves
o Mesoderm- middle layer: will be bones, muscles, blood vessels, heart, kidneys,
reproductive organs
o Endoderm- inner layer: stomach, liver, lungs
During this stage the eyes, nose, ears develop and the heart starts pumping blood
Support System for the Embryo
- The amniotic sac develops around the embryo in the mother’s uterus
- Inside the amniotic sac is amniotic fluid
- The placenta is an organ that forms to attach the amniotic sac to the uterus
- Between the embryo and the placenta is the umbilical cord
- The umbilical cord provides blood which gives nutrition, oxygen, and a way to remove waste
products
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Fetal Stage
Lasts from the 9th week till birth
Bones and muscles begin to form
At end of 3rd month: 3 inches long, liver produces bile, kidneys make urine
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Second Trimester (4th-6th months)
Fetal Stage Continued
Fetus weighs about 2 pounds (ie a quart of milk)
Eyebrows, eyelashes, and lanugo (a fine hair covering the fetus) form
Quickening occurs: the mom can feel the fetus moving
Fetus “breathes” amniotic fluid
Senses develop and eyes open and close
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Third Trimester (7th-9th months)
Organs mature such as heart, lungs, brain
Fat tissue is added to the fetus
Average baby is 7-8 pounds at birth
8th month: the baby turns upside down to get ready for birth
See p. 172 for a chart of what happens month by month
Problems in Prenatal Development
Miscarriage: the spontaneous loss of the baby before 20 weeks of pregnancy
15 – 20% of known pregnancies end in a miscarriage
Risks include:
o Women age 35 & up
o Previous miscarriage or family history of such
o Certain diseases or infections
o Exposure to alcohol, drugs, smoking, chemicals
Stillbirth: the loss of a baby after 20 weeks of a pregnancy
About one out of 200 pregnancies are stillbirths
Warning signs during pregnancy
o Heavy bleeding
o Sudden loss of fluid (before the “water breaks”)
o Absence of fetal movement after it was moving
o Painful cramping
o More than three contractions an hour before the due date
Tell doctor immediately if these occur!
If a woman has a miscarriage or stillbirth, her body must recover & both parents must deal with the
grief of losing a child
Ectopic Pregnancy
- When the fertilized egg implants itself outside the uterus
- Can lead to hemorrhaging, infertility, or death
- Tubal Pregnancy: the egg is implanted in the fallopian tube
- The zygote has no nourishment so can’t survive
- It can burst the fallopian tube and hurt the mother
- The pregnancy must be ended
Premature Labor and Birth
- Premature birth: a baby born before the 37th week
- These babies are not fully developed so have more problems ie brain, lungs
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Prenatal Testing
Tests done to determine if a fetus has a birth defect or to tell the sex of the baby
Not all pregnant mothers need all the tests
Ultrasound Imaging: using sound waves to take a picture of the fetus
o Non-invasive so very low risk
o Also called a sonogram
o Used to check the fetal position, heart rate, gender, and if there are multiple births
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- Amniocentesis: this test uses a needle inserted through the woman’s abdomen to remove amniotic fluid
o The fluid is tested for genetic diseases
o Ultrasound is used to guide procedure
o Greater risk of miscarriage
o Often used for those over age 35
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Chorionic Villi Sampling: this test takes a sample of cells from the placenta
o Done through the abdomen or vagina
o Ultrasound is used to guide procedure
o Cells are checked for genetic disorders
o Higher risks of miscarriage then amniocentesis
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Use the following words to label the parts of the baby’s world
Amniotic Fluid
Amniotic Sac
Cervix
Fetus
Placenta
Umbilical Cord
Uterus
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