Prenatal Development and Birth

Have you ever thought about what an absolute miracle your life is?

You began with two microscopic cells and NOW look at you! You are trillions of cells all working together to allow you to sit up, read, feel, digest, and even, when the time is right, make a miracle of your own.

Development begins with conception. Conception occurs when fertilization creates a zygote, a one-celled organism formed by the union of sperm and an egg.

Prenatal development is the process in which an embryo or fetus gestates during pregnancy, from fertilization until birth.

The Course of Prenatal Development

The prenatal period is divided into three phases:

1.Germinal Stage

• A zygote is created through fertilization. •Within 36 hours, rapid cell division begins, and the zygote becomes a microscopic mass of multiplying cells.• This mass of cells slowly migrates along the mother’s fallopian tube to the uterine cavity. •On about the seventh day, the cell mass begins to implant itself in the uterine wall.

2. Embryonic Stage

• Most of the vital organs and bodily systems begin to form in the developing organism, which is now called an embryo. •Structures such as the heart, spine, and brain emerge gradually as cell division becomes more specialized.

Although the embryo is typically only about an inch long at the end of this stage, it’s already beginning to look human.

3. Fetal Stage

•The developing organism, now called a fetus, becomes capable of physical movements as skeletal structures harden. •Organs formed in the embryonic stage continue to grow and gradually begin to function. •Sex organs start to develop during the third month. The fetus is far from being a passive passenger in its mother’s womb. It kicks, turns, flexes its body, somersaults, squints, and swallows, makes a fist, hiccups and sucks its thumb. It responds to both sound and vibrations, showing that it can hear and feel.

Stages of Prenatal Development

First month: Fertilization occurs.Zygote implants itself in the lining of the uterus.Rapid cell division occurs.Embryonic stage lasts from

2 weeks to 8 weeks.

Nervous system begins to develop Embryo is 1/2 inch long

6-Week-Old Embryo (Rear View)• Embryo is just over half an inch long. •As shown in this photograph, the arms and legs are just beginning to grow, and the head area is extremely large compared to its size after birth.•The embryo is shown here in the amniotic sac, which is filled with fluid to protect it.

Heart and blood vessels formHead area develops rapidlyEyes begin to form detailInternal organs grow, especially the digestive systemSex organs develop rapidly and sex is distinguishedArms and legs form and growHeart begins to beat faintlyEmbryo is 1 inch long and weighs 1/10 ounce

Two Months

Head growth occurs rapidly.Bone formation begins to form rapidly.The digestive organs begin to function.Arms, legs, and fingers make spontaneous movements.Fetus is 3 inches long and weighs 1 ounce.

Three Months

4½-Month-Old Fetus Sucking Thumb

Fetus is about 10 inches long and weighs approximately 9 ounces. As shown in this photograph, the fetus shows the reflexive movement of sucking its thumb. This activity appears remarkably similar to thumb-sucking in neonates.

Six months

Eyes and eyelids fully formedFat is developing under the skinFetus is 14 inches long and weighs 2 pounds

Nine months

Fetus settles into position for birthThe average baby is more than 19 inches long and weighs nearly 7 pounds now, but babies vary widely in size at this stage

Miscarriage and Abortion

Causes • chromosomal abnormalities• viral or bacterial infections• abnormalities of reproductive tract. • severe trauma

Maternal CharacteristicsMother’s age

-Infants born to adolescents are often premature and mortality rate of infants born to adolescents is double than that of one born to mothers in their 20s.

Nutrition-Nutrition is very important too as children born to malnourished mothers are likely to be malformed.

Emotional states-Stress during pregnancy leads to physiological changes and production of adrenaline-Maternal anxiety during pregnancy.

Teratology and Hazards to prenatal Development

The field of study that investigates the causes of birth defects is called teratology. Teratogen is any agent that causes a birth defect.

The probability of structural defects is greatest early in the embryonic period. During the fetal period they are likely to stunt growth or create problems in the way organs function.

For example, brain is most vulnerable at 15-25 daysafter conception; eyes 24-40 days; heart at 24-40 days, and legs at 24-36 days.

Maternal Diseases and Conditions

Rubella, syphilis and genital herpes are found to cause death or deformities in children born to mothers who are infected.

AIDSMothers can infect their offspring's: (1)during gestation across the placenta; (2) during delivery through contact with blood or fluids; (3) post-partum through breast-feeding.

Drugs• Tranquilizers like thalidomide, taken for morning sickness are known to cause devastating effects on fetus. e.g. if a woman took on day 26, an arm might not grow.

• Fetal alcohol syndrome (FAS) is a cluster of abnormalities that appear in the offspring of mothers who drink heavily during pregnancy.

Environmental Hazards

Radiation can cause gene mutation, an abrupt but permanent change in genetic material. Even radiation from X-rays can affect the fetus.

BirthStages of Birth:.

Stage 1(average of 12-24 hrs)

uterine contractions are 15 - 20 mins apart and lasts up to a min; contractions come closer as it progresses increasing in intensity; and dilates the cervix to an opening of 4“ for baby to move from uterus to birth canal.

Stage 2(lasts 1 and half hrs.)

head starts to move through the cervix and birth canal.

Stage 3/ Afterbirth

placenta, umbilical cord and other membrane are detached and expelled.

Delivery Complications

• Precipitate delivery is a delivery that takes place too rapidly - takes less than 10 minutes to be squeezed through the birth canal.

• If delivery takes too long, anoxia or the insufficient supply of oxygen to the infant can take place.

The breech position can cause respiratory problems and some cannot pass through the cervix and has to be delivered by a cesarean section

The Postpartum Period

It is a time when a woman’s body adjusts, both physically and psychologically, having completed the process of childbearing.

Physical adjustment:

Emotional and Psychological Adjustments:

Stages of Physical development

Name of the stage Approximate age

1. Prenatal 0 250 or 300 days

Germinal Stage 0 2 weeks

Embryonic stage 2-8 12 weeks

Fetal stage 8/12 weeks birth

Birth After an average days of 280 days.

2. Neonate 2 weeks after birth

3. Infancy First two years

4. Early Childhood From 2 6 years

5. Middle Childhood From 6 10 Years

6. Later Childhood(Pre-puberty) From 10 13 years

7. Puberty At an average of 12/13 years

8. Early adolescence From 13 15 years

9. Later Childhood From 15 20 years

10. Adulthood From 20 and beyond.

Types of Physical Development

Cephalocaudal progression Proximodistal progression

Develops from the head on down to the toes.

Develops from the central axis of the body on outward.

The infant has more motor control of the head than of the muscles lower down the body.

Trunk and shoulder movements occur earlier than separate arm movements.

Motor control follows this pattern: first the head; then the shoulders, arms, and abdomen, and finally the legs and feet.

Controls of the hands and fingers comes last.