Lecture 36- Fetal Period Flashcards
What is the first organ system to function?
Cardiovascular system (heart forms and begins to beat at week 4)
What happens at week 5-8?
Limbs start becoming clear, heart 4 chambered
Bone formation begins
External genitalia begins to differentiate
Fetal period is mainly characterized by?
Body growth
Maturation of of organs
Embryonic period is mainly characterized by?
Tissue differentiation
Formation of organs
Rapid body growth
What is the earliest period the fetus can be born prematurely and live?
Week 25+
What happens in week 9-12
Fetal length nearly doubles
Heartbeat can be detected
Gender can be assessed by looking at external genital
When does the fetus assume upside down position?
Week 30-34
What is the body fat % of fetus before birth?
16% (8% in weeks 30-34)
What is the weight of fetus before birth?
3200-3400g
Placenta is a fetomaternal organ with 2 components
Fetal (develops from x)
Maternal (develops from y)
Fetal develops from villous chorion
Maternal develops from decidua basalis (part of endometrium lining)
As the fetus grows,the chorionic cavity x, and for amniotic cavity y, degrading thr
The chorionic cavity disappears, and the amniotic cavity expands, degrading the desidua capsillaris
What is the primary function of the placenta?
Serve as an organ for exchange between the concepts and mother
Do the maternal and fetal blood directly mix?
No
Give eg’s of nutrients that enters the fetus from the endometrial spiral arteries
Water Carbs (glucose) Amino acids Lipids Electrolytes Harmones Vit’s Iron
Give ex’s of substances that leave the fetus through the umbilical arteries
Waste products like: CO2 Water Urea Uris acid Bilirubin Other substances: RBC antigens Harmones
T/f the umbilical arteries carry oxygenated blood from the fetus’s heart to the chorion
False
The umbilical arteries Carry DEOXYGENATED blood
What’s the function of HcG harmone?
It is a harmone secreted by the placenta Rescues the corpus luteum so that it continues to produce progesterone and some estrogen to Maintain endometrium lining Prepare mammary glands for lactation Prepare mother’s body for birth
What is the function of relaxin?
A harmone secreted by the placenta
- Increases flexibility of the pubic symphysis (easier to undergo labor)
- Helps dilate the uterine cervix during labor
What is the funding
Function of Human chorionic somatomammotropin hCS
Helps prepare the Navarre glands for lactation
Enhances growth by increasing protiens synthesis
Decreases glucose used by the mother and increases fat acid use by mother for ATP ( leave glucose to the fetus)
What is the function of Corticotropin releasing harmone?
Establishes the timing of birth
Increases section of cortisol TO MATURE THE LUNGS!
Describe the placenta
A discoid structure with a diameter of 15-25cm
Thickness of about 3cm
Weirgr 500-600gm
Maternal side exhibits 15-20 cotyledons (bumpy part) separated by decidual septa
Fetal surface covered by amnion
When is the placenta expelled?
Approx 30 min after birth
What is placenta previa?
Placental abnormality where the placenta is implanted lower end of the uterus (close to cervix)
Birth will be very bloody; C section os usually advised
What is placenta accreta?
Placental abnormality where the villi will adhere superficially to the muscle wall (myometrium)
What is placenta percreta?
Placental abnormality where the placenta adhered DEEP into myometrium
The amount of amniotic fluid gradually increases during pregnancy. Usually from s ml at week 12 to ml at term
50ml at week 12
1000ml at term
What’re some of the contents of the amniotic fluid?
Electrolytes Carbs A acids Lipids Proteins Harmones Enzymes A-fetoprotein Urea Desquamated fetal cells Fetal urine Fetal feces (meconium) Fetal lung tissue
Amniotic fluid is constantly being produced
How is there inflow and outflow?
Inflow directly from maternal circulation in response to osmotic forces
Fluid content also increases by secretion of urine by the kidneys into the amniotic sac
Outflow: fetus swallows amniotic fluid
AF is absorbed into fetal blood through GIT
Excess AF is removed via placenta and passed into maternal blood
What can lead to polyhydraminos?
And what is volume of amniotic fluid typically needed to diagnose this illness?
Swallowing defects (esophageal atresia or amenecephaly) Absorption defects (duodenal atresia) 2L+
When does the amnion enlarge to the point of obliterating the chorionic cavity?
Week 8
What is the function of AF?
Permits symmetrical growth of thr embryo or fetus
Acts as a barrier to infection
Prevents adherence of amnion to embryo and fetus
Permits normal fetal lung development (corticotropin releasing harmone)
Cushions the embryo/fetus
Enables movement of fetus to aid in muscle development
Maintains homeostasis
Oligohydraminos is having less that xml of amniotic fluid
What May cause oligopolyhydraminos?
400ml and below
Renal agenesis May cause oligohydraminos (no urine secretion to AF)
The umbilical cord at term is what color?
Diameter, and length?
Contains how many umbilical arteries and veins?
Pearl white 1-2cm in diameter 50-60cm long 2 umbilical arteries 1 vein
What is Wharton jelly?
Mucus connective tissue of the umbilical cord
Monozygotic twins will have resemblance in development to dizygotic twins if…
Splitting occurs at the 2 cell stage
If splitting of monozygotic twins is at blastocyst stage (2 inner cell masses) embryos will have x chorion and placenta, and have y amnion
If splitting occurs at blastocyst stage (2 cell masses)
There will be a single chorion and placenta,
But seperate amnion
If splitting occurs AFTER the formation of the inner cell mass, the embryos Will have how many amnion?
Just one amnion that will be shared
How common are birth defects?
1/16 of live births
What is the critical period (when the embryo is most at risk of abnormal development)?
During embryonic stage (3-8 weeks)
Why is the critical period not during early embryonic period?
Because rather than abnormal development occurring, death normally occurs of strong regulation mechanisms prevent abnormalities
What is the major cause of congenital malformations?
Unknown (for 50-60% of cases)
What % of congenital malformations are genetic?
Around 15%
7-8% due to mutant genes
6-7% due to chromosomal abnormalities
What % of congenital malformations is due to multi factorial inheritance?
20-25%
What % of congenital malformations is due to environmental agents?
7-10%
What are the main categories of environmental factors of birth defects?
Infectious agents
Physical agents
Chemical agents
What congenital malformations can the rubella virus cause?
Cataracts Glaucoma Heart defects Hearing loss Tooth abnormalities
What congenital malformations can cytomegalovirus cause?
Microcephalic
Visual impairment
Intellectual disability
Fetal death
What congenital malformations can toxoplasmosis cause?
Hydrocephalus
Cerebral calcifications
Microphthalmia
What congenital malformations can X-rays cause?
Microcephaly
Spina bifida
Cleft palate
Limb defects
What congenital malformations can Thalidomide cause?
Limb defects
Heart malformations
What congenital malformations can Warfarin (anticoagulant) cause?
Skeletal abnormalities (nasal hypoplasia, stippled epiphyses)
What congenital malformations can ACE inhibitors cause?
Growth retardation
Fetal DEATH!
What congenital malformations can alcohol cause?
Fetal alcohol syndrome (low birth weight)
Short palpebral fissures
Heart defects
Intellectual disability
Is Vit A healthy for the Fetus?
NO! Consuming it can cause CONGENITAL MALFORMATIONS!
small abnormally shaped ears
Cleft palate
Heart defects
Maternal diabetics and maternal obesity can cause?
Congenital malformations
What congenital malformations can Androgenic agents cause?
Masculinization of female genitalia
Fused labia
Clitoral hypertrophy
Why is ultrasound a good technique to assess fetus?
Or is noninvasive
Can assess
Fetal age and growth
Presence or absence of NTD, abdominal wall defects, heart and facial defects
Amount of AF
Placental position and umbilical blood flow
Multiple pregnancies
Why would maternal serum screening be performed?
To assess activity of Alfa-fetoprotein conc
The levels are high during week 12- 15 of pregnancy.
Then the concentration decreases
A high level of AFP after w 16 indicates neural tube defects
A low level of AFP indicates Down Syndrome
Amniocentesis
It is an invasive procedure performed performed form 15-20 week of pregnancy
Amniotic fluid is withdrawn by a needle through the anterior abdominal wall
Squamous fetal cells are cultured for testing purposes (karyotyping analysis can be used to diagnose chromosomal abnormalities)
Also assess lung maturity
What is chorionic villus samplingamd when is it indicated?
A non common, slightly invasive procedure that is conducted form weeks 8-12 of pregnancy
The tube is inserted through the vagina between the uterus and chorion with the aid of Ultrasound
Sample of chorionic villi is taken
Can be used]]]
