Prenatal dev/premature birth Flashcards
What counts as premature?
Before 37 weeks
When is the germinal period?
First 14 days
What happens during the germinal period?
Zygote divides as it travels down the fallopian tubes and eventually forms a blastocyst - ball of 16-64 cells
When is the embryonic period?
Weeks 3-8
When does the embryonic period begin?
Begins as the blastocyst implants in the uterine wall
When does organogenesis occur?
During the embryonic period (weeks 3-8)
What happens during the embryonic period?
Organs form. Layers of cells differentiate - endoderm, mesoderm, ectoderm - to form specific organs
What forms from the endoderm?
Digestive system, lungs, UT, other vital organs
What forms from the mesoderm?
Mesoderm - skeleton and muscles, circulatory ststenm, kidney, sexual organs
Arm buds and leg (tail of embryo) begin to form
Heart begins to beat 24 days (3+ weeks) into gestation
What forms from the ectoderm?
Ectoderm - hair, skin, nervous system
Ectoderm cells flatten out and turn over neural tube
What is the neural tube? What forms from it?
Top end - brain, bottom - spinal cord
Incomplete closure results in defects; anencephaly (no brain) if top not closed, spina bifida if bottom not closed
When is the end of the embryonic period? What has happened by now?
At around 8 weeks:
All organs needed to survive are formed
Facial structures fused (Abnormal: cleft palate)
Ears formed
Sexual organs developed
60% volume is head as brain development rapid, quicker than rest of body
When is the fetal period?
Last 7 months
What happens during the fetal period?
A period of rapid growth and refinement of organ systems, most importantly the lungs
Fetus become more responsive; behaviour becomes regular and integrated
When do fetuses become viable?
23 to 28 weeks
18 weeks?
Sucking thumb, breathing-like movements. Exercising muscles that will allow lungs to work.
24 weeks/6 months?
Baby respond to light outside and sounds outside and inside mother (circulatory system; blood rushing, heart beating)
Limit of viability - 50/50 chance of surviving
28 weeks/ 7 months?
Third trimester!
Fetus begins putting on weight in the form of fat
30 weeks
Lungs start producing surfactant. Keeps alveoli (pockets in lungs) open. Keeps lungs from collapsing when breathing out
Trimesters?
1st trimester - 1-12 weeks
2nd trimester - 13-28 weeks
3rd trimester - 28 weeks to birth
When is the limit of viability?
24 weeks; 50/50 chance of survival of first year
Risk factors for preterm birth?
Indigenous mothers (possibly due to poor prenatal care; leading to gestational diabetes and high BP that are not well monitored)
Young mothers (40 years)
Multiple birth
First time mums
What % of births in Australia are preterm?
7% of births
What is done for mothers who go into labour too early?
Medication to stop contractions
Steroids - Speed up lung developm ent (surfactant) before 30-32 weeks
Chances of surviving their first year
23 - 74% mortality rate (die in NICU)
24 - 44% mortality rate
Factors in predicting outcome?
Gestational age - after 24 weeks better
Birth weight - heavier do better
Gender - girls do better (oestrogen an advantage in lung development?)
Multiple or singleton - singleton do better
Steroids - if mum’s labour is stopped and given steroids, baby does better
