Pregnancy and Birth Chapter 17.2 Page 555-560

Objectives Describe the process of fertilization and implantation Trace the development of a fertilized egg to the birth of a baby List the events of birth Explain how a mother’s health can affect the health of her baby

Key Terms Fetus Zygote Blastocyst Embryo Amniotic fluid Placenta

A process: From fertilization to growing fetus Fertilization is the union of a mature egg cell with a single sperm Sperm cell bind to the egg while it is in the fallopian tube Chemicals in the “head“ of the sperm cell weaken the outer coating of the egg A single sperm cell breaks through and the egg changes chemically to prevent other sperm from entering The genetic materials combine and fertilization is done

The Zygote (fertilization to 2 days) The egg and sperm combine to form a new structure called the zygote All of the trillions, (1,000,000,000, 000), 0f cells are generated by this single cell If the single cell separates into two or more separate groups at this early stage it may result in multiple births, (twins or triplets) If more than one egg is fertilized, there are multiple zygotes, (fraternal twins or triplets)

The Embryo (2 days to 2 months) As the zygote divides and moves toward the uterus it becomes a ball of cells called the blastocyst The blastocyst makes a hormone called HCG that tells the ovary that pregnancy has begun As it attaches to the uterus it now is called an embryo and has no major structures yet The amniotic sac and placenta begin developing

The Fetus (2 months after fertilization) The placenta nourishes the fetus Nutrients and oxygen are provided Wastes and CO2 are removed There is no contact between the blood of the fetus and the mother because of this barrier The umbilical cord is the point of connection The fetus grows for about 9 months and develops specialized structures

Trimesters First trimester Second trimester Third trimester Major organs have begun to form Eyes, ears, liver, lungs, heart and brain Bones, muscles, arms, and legs Second trimester Movement, heartbeat, blinking Third trimester All organs rapidly complete development The brain grows rapidly, (and continues after birth) The fetus gains weight

Birth The timing of birth Labor Babies born before 35 weeks are considered premature or “preemies” Babies are generally born at week 36 to 41 Labor Contractions of the uterus May be short and “mild” or long and “agonizing” Increase in frequency and pain as labor continues May last 12 hours or more

This diagram tells it all… The amniotic sac will break and the fluid leaks out The cervix must dilate to 10 cm or 4 inches The baby is still attached by the umbilical cord to the placenta The uterus “pushes” the baby through the cervix and down the vagina The umbilical cord is cut The placenta is the afterbirth

Healthy Baby/Healthy Mother A mother that mistreats her body is mistreating the baby Dangerous substances in the mother’s blood can pass to the fetus Illnesses, (viral infections) Drugs Nicotine, alcohol, caffeine