Aim: What events occur during pregnancy and childbirth?
Class notes: Conception and pregnancy:
Egg- Female sex cell. Contains the mother's DNA.
Sperm- Male sex cell. Contain the father's DNA. Determines gender- if the sperm that fertilizes the egg has an X chromosome, the fetus will be female; if the sperm carries a Y chromosome, the fetus will be male.
Conception/Fertilization- The union of sperm and egg. Only one sperm can fertilize the egg.
Blastocyst- The proper term for an egg that has been fertilized by sperm. At this stage, the fertilized egg begins to divide within itself, forming a ball of cells called a blastocyst. If, during this division process the egg completely divides, identical twins will result.
Ectopic pregnancy- Occurs when a blastocyst implants itself into tissue outside of the uterus (usually in the Fallopian Tubes).
Implantation- Attachment of the fertilized egg/blastocyst to the wall of the uterus.
Pregnancy- Occurs when implantation occurs. Usually, pregnancy occurs about one week after conception.
Embryo- Term used to describe the fertilized egg after conception. It will be called an embryo until about week 8 of pregnancy.
Yolk Sac- Sustains the growing embryo until the placenta is fully formed in the uterus (for the first 12 weeks).
Placenta- Acts as a filter and supplier of nutrients for a growing fetus. The placenta is attached to the wall of the uterus. Nutrients, and oxygen from the mother pass through the placenta on their way to the fetus. The placenta filters out many (but not all) harmful substances that may be in the mother's bloodstream. The placenta also keeps the bloodstream of the mother seperate from the bloodstream of the fetus.
Fetus- Term used to describe the embryo after about 8 weeks.
Umbilical Cord- A cord that connects the placenta to the fetus. This cord carries the nutrients, oxygen and blood necessary for the fetus to survive and grow.
Amniotic Sac- Thin "bag" that surrounds the fetus. It helps protect the fetus as it develops inside the uterus.
Amniotic Fluid- Also known as the woman's "water." This fluid is contained in the amniotic sac and surrounds the fetus. It protects the fetus.
After students have completed the vocabulary, have them use the vocabulary terms to write a paragraph that explains how two separate cells combine to form a developing fetus. The paragraph might sound like this:
After intercourse, the male sex cell (sperm) and the female sex cell (egg) meet. The sperm imbeds itself into the egg in a process called conception, or fertilization. The fertilized egg, or blastocyst, begins to travel down the fallopian tubes toward the uterus. Once it makes it to the uterus, it implants itself into the lining of the uteran wall. Once this implantation occurs, pregnancy has occurred. If the blastocyst implants itself outside of the uterus, a woman may have an ectopic pregnancy, which can be very dangerous. After the blastocyst implants, it is called an embryo. It uses the nourishment from its yolk sac until the placenta is formed. Attached to the placenta is the umbilical cord, which connects the embryo and the placenta. After the placenta is fully formed, the embryo is now called a fetus, and continues to grow and develop, living off of the nutrients, blood and oxygen it gets from its mother. It is protected by a thin membrane called an amniotic sac and is surrounded by amniotic fluid.
Signs of pregnancy:
-Missed mestruation: during a pregnancy, a woman stops menstruating until the baby is born.
-Enlarged, tender breasts.
-"Morning" sickness: some women feel sick to their stomach, particularily during the first trimester (three months).
-Weight gain, particularily in the abdominal area.
-Fatigue, particularily in the first trimester.
-Increased frequency in urination.
Prenatal care:
A woman should see a doctor when she first suspects she is pregnant and get prenatal care. Prenatal care involves:
-Frequent check-ups- to check the health of mother and fetus.
-Prenatal vitamins
-Testing- to test for fetal abnormalities, gestational diabetes (diabetes during pregnancy), STI's or other conditions that may be dangerous for mother and fetus.
-Preparation for labor and delivery.
Taking care of herself and her baby during pregnancy will reduce the risks of complications to a woman's pregnancy. Drugs, including tobacco and alcohol, poor nutrition, and lack of exercise can be very harmful to both the mother and the fetus.
Pregnancy
Pregnancy is divided into three stages called trimesters. A normal pregnancy (or period of "gestation") is 40 weeks. The 40 weeks is calculated from the first day of a woman's last period, which is how doctors determine a woman's "due date." A woman can deliver anywhere from 36-42 weeks in order for her pregnancy to be considered "full term." Any deliveries before 36 weeks is considered a "premature" delivery.
1st Trimester:
Week 1-12- This trimester begins at conception and ends at week 12, usually after the placenta has been formed. Following conception, the fertilized egg travels down into the uterus where it embeds itself into the lining of the uterus. From the time of conception, the fertilized egg begins to divide, and reproduce. Shortly following conception, the mother suspects she is pregnant when she does not menstruate. Throughout pregnancy, cells continue to divide. Some cells will become bones, others will become nerves, until an entire fetus develops. Some cells will also become the placenta and umbilical cord, which is the fetus's lifeline. By the end of the first trimester, the placenta and the umbilical cord will be created, and will supply the fetus with what it needs for survival for the remainder of the pregnancy. During the first trimester, the embryo is doing a lot of growing:
* Week 3-4 the embryo has a heart beat and all of the organs are forming.
* By the end of 6 weeks, fingers, toes, ears and skin are forming.
* At week 8 all organs have begun to develop.
* By the end of week 12 all of the organs are formed and functioning.
Many changes take place in a woman's body during this time, although she may not even realize she is pregnant until about week 6-8. A woman may experience fatigue, breast tenderness, nausea and vomiting, hormonal changes, frequent urination and a missed period. These are all signs of pregnancy, although some women may not experience many of these signs.
2nd Trimester:
Week 13-28: During this trimester the fetus continues to look more and more like a human baby. It's organs become fully-functioning and it's senses begin to develop. It's movement can also be felt by the mother. If born (prematurely) at the end of this trimester, survival is possible.
* Month 4- arms, legs, fingers and toes are completely formed. THe fetus can close its fingers, curl its toes, suckle, swallow and even squint its eyes. THe circulatory system and urinary systems are now operating. At this point, the fetus is about 3-4 inches.
* Month 5- THe fetus is now covered with fine hair. Eyelashes and eyebrows can be seen. THe fetus is very active, and fetal movement can be felt by the mother. THe fetus is now approximately 12 inches and weighs about 1 pound.
* Month 6- THe eyelids open and shut, the fetus now has distinct fingerprints and toe prints. It has grown to about 14 inches and weighs 2 pounds.
* Month 7- THe fetus can suck its thumb, hiccup, cry, and respond to outside stimuli, such as music, pain, and bright light. THe fetus weighs about 3 pounds and is 15-16 inches long.
The second trimester is usually the most comfortable one for the mother. If she experienced any sickness during the first trimester, it ususally subsides during the second trimester. Because the placenta is fully formed, the mother has more energy and is not as tired. Although she can feel the movement of the fetus, she may not even show that she is pregnant.
3rd Trimester:
Week 29-40: During this time the fetus continues to grow and gain weight. During the last 4 weeks of pregnancy, the fetus may gain up to 1/2 pound each week. THe lungs also get ready during the third trimester, so that the fetus can breathe on its own after delivery.
* Month 8- THere is a great deal of brain growth and development during this time. THe fetus is also storing the necessary fat it requires for survival. By the end of this month, the fetus is approximately 18 inches long and weighs 5-6 pounds.
* Month 9- THe last few weeks of pregnancy are mainly a growth period for the fetus, making it capable of surviving on its own. By the end of the ninth month, the fetus is full-size and capable of surviving on its own.
How does the health of the mother affect the development of the fetus?
Stress, poor diet, lack of sleep, drug use and alcohol will all have a negative impact on the development of the fetus. Many babies are born prematurely, low birth weight, learning disabilities, addicted to drugs, with behavioral problems, etc. due to the poor health of the mother. However, a mother may be totally healthy and still have a baby that is born premature, low birth weight, with behavioral problems or learning disabilities.
Stages of Labor
Stage 1- Contractions cause the cervix to dialate to 10 cm. This can take over 24 hours to complete.
Stage 2- Delivery of baby.
Stage 3- Delivery of placenta.
The hormone oxytocin is responsible for stimulating labor.
After the baby is delivered, a woman will start producing milk in her breasts to feed the baby. The uterus will also contract and start shrinking down back to its normal size. During this time, the mother will experience cramping and bleeding, like a heavy period. Bleeding may continue for up to 2 weeks, until the uterus is back to its normal size.