What are some early signs of pregnancy?

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Stages of Prenatal DevelopmentZygotic (or Germinal) Stage 0-2

weeksEmbryonic Stage 2-8 weeksFetal Stage 9-40 weeks

ConceptionConception occurs when a sperm cell

penetrates and fertilizes an egg cellSuccessful conception depends on

ovaries releasing one healthy egg cellegg cell migrates most of the way down the fallopian tube

One sperm must penetrate the ovum to form a zygote.

Germinal PeriodBegins when egg is fertilized in the fallopian tube.

Period of rapid cell divisionEnds 2 weeks later when the zygote is implanted in the wall of the uterus

Germinal Period

Embryonic PeriodFrom 2 to 8 weeks after conception

Cell differentiation intensifiesLife support systems for the embryo develop

Organs Appear

Prenatal Structures

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At 2 weeks, the embryonic disk as 3 layers:Entoderm: from which develops

pharynx, tonsils, thyroid, trachea, lungs, digestive system, bladder, urethra

Mesoderm: from which develops muscles, bones, circulatory system, lymph system, kidneys, gonads

Ectoderm: from which develops skin, hair, nails, sense organs, nervous tissue

Fetal PeriodFrom 9 weeks after conception to birth

Increase in size and systems begin to function

Age of viability: 22 to 28 weeks

First MonthBy 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.

First Month

Two MonthsThe 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.

Two Months

Three MonthsBy 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. Genitals can be now identified as male or female.

Four MonthsFetus is about 6

inches long and weighs 4 to 7 ounces. His heartbeat can be heard clearly. This is when you may feel your baby's first kick.

4 months

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 12 inches long and weigh almost a pound. Fetus is more active.

Six MonthsEyebrows 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.

6 Months

Seven MonthsBy 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

Eight MonthsYour 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.

Nine MonthsYour 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.

Happy Birthday!!!

Factors Affecting to Prenatal Development

General Risk FactorsTeratogens: Diseases, Drugs, and Environmental Hazards

How Teratogens Influence Prenatal Development

Prenatal Diagnosis and Treatment

General Risk FactorsNutrition: adequate amount of food, protein, vitamins, & minerals

Stress: decreases oxygen to fetus and weakens mother’s immune system

Mother’s Age: neither too young, nor too old

Prescription and Nonprescription Drugs – Several drugs used by the mother that have negative effects on the embryos and fetuses.

Psychoactive drugs are used to alter states of consciousness, modify perceptions, and change moods. The effects of alcohol, nicotine, and illegal drugs on the fetus are well-documented.

Incompatibility of blood types where the fetus’s blood is RH positive ad the mother’s is RH negative cause antibodies to attack the fetus, resulting in serious, often life-threatening damage.

Environmental hazards of the modern world can cause chromosomal abnormalities. Exposure to toxins, radiation, pollutants, and excess heat can all contribute to a negative impact on the fetus.

Other maternal factors such as infectious diseases (Rubella, Syphilis, AIDS), all have varying degrees of impact on the fetus. Also considered are emotional stress, age, and nutrition of the mother.

Paternal factors can impact fetal growth such as pesticides at the workplace, smoking and diet.

Teratogens: Diseases, Drugs, and Environmental Hazards

• Many diseases pass through the placenta directly and attack the fetus

• Potentially dangerous drugs not limited to cocaine but include alcohol and caffeine

• Environmental hazards are treacherous because we’re often unaware of their presence

How Teratogens Influence Prenatal Development

Not universally harmfulHarm particular structures at a particular point in development in particular animals

Effects of Teratogens

Prenatal Diagnosis and Treatment

Diagnosis: ultrasound, amniocentesis, and chorionic villus sampling can detect physical deformities and genetic disorders

Treatment: fetal medicine and genetic engineering are experimental

Prenatal Diagnosis

Amniocentesis Chorionic Villus Sampling

Labor and DeliveryStage 1: starts when the muscles of the uterus contract and ends when the cervix is fully enlarged (about 10 cm)

Stage 2: baby is pushed down the birth canal

Stage 3: placenta is expelled

Three Stages of Labor