Nurse

1. Germinal period- 2 weeks, zygote divides many times through mitosis forming a blast cyst--reaches the uterus about day 6 where it will spend the next 39 weeks or so ( 40 week is full term pregnancy)

Embryonic period-occurs from the third to eighth weeks of pregnancy--major organs begin to take shape-called organ genesis-outer layer amnion water tight membrane

Fetal Period- 9th week of pregnancy until birth-major growth period organs are formed but continue to develop until birth for some organs (lungs) recognizable sex organs (sex determination on ultrasound at around 20-25 weeks of pregnancy) Respond to light and sound in utero (24-25 weeks) patterns of organized behavior exhibited (sleep, breathing, swallow patterns more organized and predictable (stable) wake and sleep periods of an infant)

2. Germinal period--Day 1 fertilization usually occurs within 24 hours of ovulation

Days 8-14 the blast cyst becomes fully embedded in the wall of the uterus and has about 250 cells

Embryonic Period:

Week 3-now an embryo, 3 layers emerge ectoderm, mesoderm, and endoderm

Week 8- many structures and organs are present. Ovaries and testes are evident; embryo begins to appear more human-like.

Fetal Period-

Week 9- bone tissue emerges and embryo becomes a fetus; head is large compared to rest of body (50%); can open and close mouth and turn head.

3. Teratogen-any disease, drug or environmental agents that can harm a developing fetus.

4. Critical period- the periods of time of prenatal development that teratogen is likely to cause defects or abnormalities in a fetus (some say conception to birth, but it depend on the type of teratogen and amount of exposure. Alcohol, recreational drugs (street drugs) tobacco smoke have been said to affect development from germinal period to birth)

The more exposure (dosage and duration) the more likely serious damage will occur.

5. Drugs:

Thalidomide:

This prescription drug was proven to cause major birth defects in the 1950's; was used for morning sickness. Thousands of women who took Thalidomide in the first two months of pregnancy, delivered babies with all or parts of limbs missing, feet or hands attached directly to the torso like flippers, deformities in eyes, ears as well as the heart. Was banned for many years and is now in use again.

If taken 20-22 days after conception baby likely to be born without ears

22-27 days after conception- missing or small thumbs.

27-33 days after conception- baby often had stunted legs