Fetal Stages of Growth

0-2 weeks of gestation

Pre embryonic stage

What occurs during the pre embryonic stage?

1. day 1 = mitiotic cell division

2. 3 days post fetilization cell becomes a 16 cell morula

3. day 5 = blastocyte enters the uterus

4. day 6-10 = implantation in upper uterus

What occurs between 3-8 weeks of gestation?

All major body organs and external features are complete including interal organs

blastocytes becomes __________ at 2 weeks gestation

embryoblast (inner cell mass)

trophoblast becomes _____________ at 2 weeks gestation

placenta

When does the baby heart begin to beat?

At 3 weeks

Germ layer: CNS, special senses, skin and glands

Ectoderm

Germ layer: Circulatory, reproductive organs, muscoloskeletal, urinary

Mesoderm

Germ layer: Digestive, respiratory, liver, pancreas

Endoderm

Which week of gestation does the neural tube close?

At 4 weeks

When is the embryo heartbeat visible on ultrasound?

At 4 weeks

Embryonic stage length

3-8 weeks

Fetus stage length

9 + weeks (until birth)

When does the lanugo form?

At 13-16 weeks cover whole body by 17-23 weeks

The fine hair that develops on fetus body

Lanugo

When is the vernix formed?

By week 20

Cheesy white substance that protects and water proofs the skin d/t fetus sitting in amniotic fluid

Vernix

Substances encountered during pregnancy which can lead to birth defects

Teratogen

When are teratogens the most harmful for the fetus?

During the first 8 weeks of gestation

Medication Pregnancy categories:

Examples: Folic acid

Category A

Medication Pregnancy categories:

Penicillin, Zyrtec

Category B: Animal studies show of risk, but no good human studies have been done

Medication Pregnancy categories:

Macrobid

Category C: No adquate evidence or human studies exist

Medication Pregnancy categories:

Tertracyline, Paxil, Dilantin

Category D: Evidence of fetal risk is clear-cut, but the benefits may outweigh the risks

Medication Pregnancy categories:

ETOH, Warfarin, DES, Valporic Acid, Accutane

Category X: proven fetal risks clearly outweigh any benefit

When are the fetal lungs formed?

At week 6

What occurs during 28-31 weeks of gestation?

• Fetus is capable of breathing air → still not enough surfactant

• vertex position (vaginal birth)

• vernix and lanugo still present

• fetus could develop RDS d/t not having enough surfactant

• subcutaneous fat develops

• fetus is red, cheesy, hairy, and smaller

When does the aveoli develop?

24-27 weeks which increases fetus chance of survial outside the womb

• help provide fetus with energy and maintains temp/keep fetus warm

• developed during 17-23 weeks of gestation

brown fat

At which weeks of gestation does the pulmonary and nervous system mature?

33-38 weeks