Pregnancy and Birth Prenatal Development

Objectives: To name the three stages of pregnancy Describe the prenatal development during each of the three stages of pregnancy Describe how the embryo is protected and nourished Describe the stages of childbirth

What Happens Before Birth? When an egg leaves the ovary, it is covered by a protective layer of cells

What Happens Before Birth? The Fallopian tube is lined with a layer of cilia to help move the egg down to the uterus.

What Happens Before Birth? Sperm swim through the cervix and uterus and into a fallopian tube to meet an egg.

What Happens Before Birth? Sperm secrete an enzyme the erodes the egg’s outer layer to allow penetration.

What Happens Before Birth? When sperm enter the vagina – they swim through the uterus and fallopian tubes. Fertilization occurs in fallopian tubes

Prenatal Development Prenatal development is the development of the baby during the period before birth. Before birth, the zygote develops first into an embryo and then into a fetus. Zygote Embryo Fetus

Period of the Zygote Super brief When the fertilized egg divides into 2 cells

Period of the Embryo From the 2 cell stage through the 8th week After zygote divides into two cells, the cells continue to divide as they travel to the uterus. Embryo is over 100 cells by the time it reaches the uterus. Ball of cells attaches to the lining of the uterus Placenta forms around week 4

Attaching to wall of the uterus

Period of the Fetus From the end of 8 weeks until birth Internal organs start to develop The body parts, organs and systems which were formed during the embryo period will become much more developed and begin to function. During the fetal period the baby may increase in length as much as twelve inches.

Protecting and Nourishing the Embryo Membranes and structures that from in the uterus during pregnancy protect and nourish the developing baby

Protecting and Nourishing the Embryo Membranes and structures that from in the uterus during pregnancy protect and nourish the developing baby Membranes Amniotic sac Placenta Structures Umbilical Cord

Amniotic Sac Surrounds the embryo and is filled with fluid Fluid cushions and protects the embryo and fetus

Placenta Links the embryo to the mother Allows substances to be exchanged between bloodstreams

Umbilical Cord Ropelike structure that forms between the embryo and placenta. Contains blood vessels from embryo that link it to the placenta

What Happens During Childbirth? The birth of a baby takes place in three stages: labor, delivery, & afterbirth

Labor 1st stage of birth Contractions of uterus cause cervix to open May last from 2 – 20+ hours

Delivery 2nd stage of birth Head first – hopefully Can last several minutes – 2 hours After umbilical cord is cut

Afterbirth 3rd and final stage of birth Soon after delivery Muscles in uterus contract Pushes placenta and amniotic sac out Usually lasts less than 1 hour

Birth and the Baby During birth, pressure from contractions causes baby’s O2 supply to decrease. Baby’s heart rate increases because of the release of adrenaline in endocrine system

Multiple Births Twin births are most common multiple birth Two types of twins Identical 1 zygote splits into 2 embryos Fraternal 2 sperm fertilize 2 eggs

Timeline of pregnancy conception 1 month pregnant 2 months pregnant

What two things are happening during labor? Questions for review What is the placenta? How many eggs and sperm are needed for the development of identical twins? What two things are happening during labor?

More questions… The umbilical cord forms between what 2 “things”? What is the function of the amniotic sac? After fertilization occurs, what are the 3 stages of baby development? When does a zygote become an embryo?

Stop here If interested…more detail of what happens each month is in the following slides.

Period of the Embryo First Month By the end of the first month, the embryo is about 1/10 of an inch long. The heart, which is no larger than a poppy seed, has begun beating.

Embryo -Two Months The embryo is about 1 inch long and has distinct, slightly webbed fingers. Veins are clearly visible. The heart has divided into right and left chambers.

Three Month Fetus By now the fetus is 2 1/2 to 3 inches long and is fully formed. He has begun swallowing and kicking. All organs and muscles have formed and are beginning to function.

Fetus - Fourth Month Your baby is covered with a layer of thick, downy hair called lanugo. His heartbeat can be heard clearly. This is when you may feel your baby's first kick

Fetus- 4th Month

Fetus Five Months A protective coating called vernix caseosa begins to form on baby's skin. By the end of this month, your baby will be nearly 8 inches long and weighs almost a pound

Fetus Six Months Eyebrows and eyelids are visible. Your baby's lungs are filled with amniotic fluid, and he has started breathing motions. If you talk or sing, he can hear you.

Six Month Fetus

Fetus Seven Months By the end of the seventh month, your baby weighs about 3 1/2 pounds and is about 12 inches long. His body is well-formed. Fingernails cover his fingertips

Fetus Eight Months Your baby is gaining about half a pound per week, and layers of fat are piling on. He has probably turned head-down in preparation for birth. He weighs between 4 and 6 pounds.

8th Month Fetus

Fetus Nine Months Your baby is a hefty 6 to 9 pounds and measures between 19 and 22 inches. As he becomes more crowded, you may feel him move around less.

Lightening Sometimes during the ninth month, the baby’s weight seems to shift down and the mother feels more comfortable in her upper abdomen. This is called Lightening This means the baby has dropped into the birth canal and birth is not far off

Weight Gain Baby 7.5 lb Placenta 1.5 lb Uterus 2 lb Amniotic Fluid Extra Blood & Water Retention 4.5 lb Breast Tissue 3 lb Maternal Stores of Protein 4 lb The recommended weight gain for the average woman during pregnancy is 25-30 pounds and is distributed as follows: