Minnesota State University Moorhead



Chapter 4 – Prenatal Development and Birth

Prenatal Growth

Three main periods of prenatal development

Germinal Period (1st two weeks after conception): rapid cell division and beginning of cell differentiation

Embryonic Period (3rd through 8th week): basic forms of all body structures develop

Fetal Period (9th week until birth): fetus grows in size and matures in functioning

The Germinal Period

Zygote begins duplication and division within hours of conception

Development of the placenta

Organ that surrounds the developing embryo

Sustains life via the umbilical chord

Implantation (about 10 days after conception)

Developing organism burrows into the placenta that lines the uterus

The Embryonic Period

Embryo

3rd through the 8th week after conception

Eyes, ears, nose, and mouth form

Heart begins to pulsate

Extremities develop and webbed fingers and toes separate

The Fetal Period

9th week after conception until birth

Genitals form and sex hormones cause differences brain organization

Cephalocaudal and proximodistal growth

Heartbeat detectable via stethoscope

Cortex is not fully mature at birth

Brain at birth is biggest part of baby

Age of viability

Age at which a preterm newborn may survive outside the womb with medical care

About 22 weeks after conception

Brain is able to regulate basic body functions

Birth

Fetal brain signals the release of hormones to trigger the mother’s uterine muscles

Labor begins

Average duration for first babies: 12 hours

Apgar scale

Quick assessment of newborn’s heart rate, breathing, muscle tone, color, and reflexes

Completed twice (1 minute and 5 minutes after birth)

Score of 0, 1, or 2 in each category

Desired score: 7 (total) or above

Medical Assistance

Cesarean Section (c-section) Surgical birth

Fetus can be removed quickly

Rates and reasons for c-sections vary

Less trauma for the newborn but slower recovery for the mother

Subsequent cesarean deliveries may be necessary

Newborn Survival

Infant mortality has decreased due to better medical care

1900: 5%

Today: ................
................

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