Mod 1 fetal development & Maternal problems Flashcards
1.1 Fetal Development, Prenatal Assessment and Pregnancy 2.2 Maternal Health & Prenatal Complications
what’s the age range for a neonate?
First 28 days of life
What is age of viability?
- 22-23 weeks
- Age fetus can be resuscitated at delivery and survive w/o significant morbidity
Extremely preterm or extremely low birth weight can be expected to be at what range of term?
< 28 weeks
What is a very preterm baby?
Less than 28-32 weeks
What is a moderate to late preterm range for a fetus?
32-37 weeks
Range for baby at term?
37-42
Define Post term range for a baby?
> 43 weeks
What are the ranges of each trimester?
1st trimester = 0-13 weeks
2nd trimester = 14-27 weeks
3rd trimester = 28 weeks-delivery
what are the 3 embryonic germ layers?
Ectoderm (outer)
Endoderm (inner)
Mesoderm (middle)
5 phases of fetal lung development
Embryonic
Pseudoglandular
Canalicular
Saccular
Alveolar
What is the estimated date of arrival (EDD) taken from?
From date of last menstrual cycle
What is viability of the fetus dependent on?
Generally speaking, Gestational age bc it determines how much of the babe has developed. That being said:
- Stability and maturity of CNS (and protective mechs)
- Circulatory system
- Respiratory system
- musculoskeletal system
- Integrity of the skin
What develops in the ectoderm?
- CNS and PNS
- Sensory epithelia of eyes, inner ears, nose
- Skin (epidermal layer)
- Teeth (enamel)
What develops in the ectoderm phase from the CNS and PNS?
CNS: Brain and spinal chord
PNS: Cranial + spinal nerves
What develops from the mesoderm layer?
Cardiovascular system
lymphatic system vessels
All connective tissue and muscle tissue
- skin
- kidneys and ureters
- reproductive tissue
- the 3 major body cavities
- serious lining of organs
- Teeth
What develops from the endoderm layer?
Digestive system
Respiratory system
Urinary system
Liver and pancreas
Tonsils etc.
epithelial lining of auditory tube and tympanic cavity
what are the 3 stages of development (for pregnancy)?
- Conception
- Embryonic stage
- Fetal development
What happens during the conception stage of development?
- What is the range?
The ovum and sperm unite
- Occurs during the First 2 weeks of pregnancy
What happens during the embryonic stage of development?
What is the range?
- Embryo development
- major organs (heart + CNS begin to develop)
- Occurs during weeks 3-8, but can continue to week 12
What happens during fetal development?
When does it occur?
Most lung development occurs during this stage
occurs @ weeks 13-40
what happens 5 days after fertilization of a egg?
(5 things happens)
- blastocyst combines w/tissue in the endometrium to form the chorionic membrane
- outer tissue envelops the embryonic structure and forms the amniotic sac
- Amniotic sac surrounds the entire embryo
- Embryo attaches via umbilical stalk -> turns into umbilical cord
- umbilical cord vili (where gas exchange occurs) connects to outer lining of the chorion
During Fetal development, in what order do the following develop?
- Alveolar sac
- Bronchi
- Terminal Bronchioles
- Respiratory bronchioles
- Bronchioles
- Alveolar ducts
- Bronchi
- Bronchioles
- Terminal Bronchioles
- Respiratory bronchioles
- Alveolar ducts
- Alveolar sacs
Why is age of viability important?
- Babe can be resuscitated (wks 22-23)
- Surfactant typically developments in weeks (24-28)
- Surfactant is immature at week 26 and matures around weeks 28+
- Surfactant is crucial to gentle ventilation
When does the Embryonic phase generally occur?
- and what is most notable about this phase?
- conception to around week 8
What are some complications during the Embryonic phase of development?
- When the trachea forms, there can congenital defects (tracheoesophageal atresia, trachea stenosis).
- Diaphragmatic Hernia
What is most notable about the embryonic phase?
- The respiratory epithelium begins to grow
- pharynx forms from endoderm
- Lung buds form (left and right)
- Diaphragm forms
- Pulmonary interstitial, smooth muscle, and blood vessels begin to form
When does the pseudoglandular phase occur?
Arounds week 8-16
What is most notable about the pseudoglandular phase?
Formation of conduction airways (complete) and development of Terminal bronchioles (immature)
- lobes complete ( 3 right, 2 left)
- cartilage beings to form around airways
- Cilia develop
- presence of mucus, goblet cells, and bronchial glands
- Pulmonary vasculature develops
- Larynx begins developing
- Oropharynx and nasopharyngeal develop
what are some complications that occur during the pseudogalndular phase?
Congenital disorder can development in the oropharynx/nasopharyngeal
- Choanal atresia
When does the Canalicular phase occur?
Weeks 16-26
What is most notable about the Canalicular phase?
- surfactant becomes to form.
- they’re viable because we can provide it for them
they also have the framework for that (systems) - can start to test at this range aka can sample amniotic fluid to gauge condition
What develops in the canalicular phase?
- Immature surfactant (begin to differentiate between type I and type II cells)
- Capillary network forms
- Airway complete branching
- Acinar units appear
- Fetal lung fluid
When does gas exchange become possible in a developing fetus?
During the Canalicular phase, around weeks 22-24
What is apart of the Acinar?
- Respiratory bronchiole
- alveolar ducts
- alveolar sacs
What are premature neonates susceptible to during the canalicular phase?
RDS
when does the saccular phase occur?
Weeks 26-36
what is notable about the saccular phase in fetal development?
Last gen of growth in airways
- Immature alveoli (saccules) form
- Surfactant Matures @ week 35
When does the alveolar phase occur?
Week 36 to term
What is notable about the alveolar phase of fetal development
- Immature alveolar saccules mature to alveolar sacs
- O2 uptake increases
- Alveoli proliferate into millions by full term birth (continues till ages 8-10)
When would you provide glucoticoidsteroids?
Given systemically to moms to help accelerate lung maturation of baby
- its a type II pneumocytes
what is pulmonary hypoplasia
When there is a growth limitation in lung development
what are 3 tests for examining fetal lung maturity?
- L/S Ratio
- PG presence
- S/A ratio
In a fetus what is hypoxic pulmonary vasoconstriction and why does it occur?
Hypoxic pulmonary vasoconstriction occurs when there is low O2 in the lungs, causing the arteries to all constrict, increasing resistance in the pulmonary arteries.
What conditions would you expect to increase lung maturation of a fetus?
- Giving birth to multiples
- Glucocorticoid steroids (Type II pneumocytes)
In a fetus, what conditions would slow down lung development?
- Maternal diabetes
- Chest wall compression (diaphragmatic hernia)
- Oligohydramnios
- Diminished respirations in utero
- Other hormonal/metabolic abnormalities
what is Oligohydramnios?
Decreased amniotic fluid
Immature surfactant production begins in which phase?
Canalicular phase
when does immature surfactant mature?
at 35 weeks gestation
What does mature surfactant gain when it reaches full maturation?
lipids and glycoproteins
- phosphatidylcholine
- and Phosphatidylglycerol (PG)
What phases does surfactant mature?
Saccular, but potentially Alveolar phase as well.
What are characteristics/traits of Type I pneumocytes (Surfactant)?
Type 1 pneumocytes facilitate gas exchange
- structure of the alveoli
- Gas permeable membrane area
- flat
What are characteristics/traits of Type II pneumocytes (Surfactant)?
Cuboidal in shape, they produces:
- Type I cells,
- surfactant
- fetal lung fluid
Infants born before mature surfactant is present are at risk of what?
- what is the treatment?
At risk of RDS
- admin surfactant within 1 hour after birth
What is the golden hour?
Time frame to admin surfactant to a baby lacking mature surfactant
- basically supportive management in the first hour that determines if a babe lives.
Factors that affect surfactant
- Aspiration syndromes
- Meconium
- Severe bleeding (pulmonary hemorrhage)
- Amniotic fluid
- PDA
How is fetal lung fluid different from amniotic fluid?
- Lower pH, HCO3, and protein levels
- Higher sodium and chloride concentrations.
How much fluid do fetal lungs secrete a day?
250-300 mL
What do we analyze to determine if fetal lungs are at full maturity?
Fetal lung fluid
How is fetal lung fluid removed from a baby at birth?
- Decreased production in late gestation
- Contractions during vaginal delivery
- Lymphatic absorption after birth
Fetal Lung Maturity Testing: What is the L/S ratio and what do we ideally want?
Tests the ratio of Lethicin to sphingomyelin
- Week 31-32 = 1:1
- Week 35 gestation 2:1 (only 2% chance of RDS @ this ratio)
- we want a ratio of 2:1 or greater at week 35
What does the ratio 2:1 mean from the L/S ratio?
The lecithin to sphingomyelin ratio of 2:1 or greater is characteristic of mature fetal lungs (around wk 35)
- Fetuses delivered prior to this gestational age are at increased risk of neonatal respiratory distress syndrome. (before week 35)
Fetal Lung Maturity Testing: what is PG presence?
- why is it important?
- when does it appear
- It indicates surfactant maturity
- Appears around week 35
- Good predictor of lung maturity, but not maturity
- full name of PG is Phosphatidylglycerol/Phosphatidylcholine
Fetal Lung Maturity Testing: What is the S/A Ratio?
- what does it tell us?
- why is it important?
Measures concentration of albumin and surfactant.
- only requires a small amount of amniotic fluid
- > 55 mg of surfactant per 1 g of albumin indicates maturity
- < 40 mg surfactant per 1 g of albumin indicates immature
What is the primary function of amniotic fluid?
- Protects the fetus from injury (cushions)
- Control thermal environment
- Assists in effacement and dilation of the cervix during labour
What is amniotic fluid composed of?
- Maternal blood products
- Amniotic cells
- fetal skin, hair, & urine
How much amniotic fluid is produced in the period of a term?
1.5L by term
- Begins production at week 10, 30mLs are produced a day.
How much fluid does a fetus swallow a day?
500 mLs, it also excretes the same amount of hypotonic urine back into the mix
Fetal Heart Development: Label the following structures
How does fetal circulation differ from adult circulation?
Blood is mostly shunted around the lungs
Fetal circulation: Describe how vascular resistance differs from adults
Fetus have high vascular resistance in pulmonary circulation and low vascular resistance in the systemic circulation.
Why do fetus’s have low systemic vascular resistance?
The placenta
- It has a large volume (surface area) and has a very low resistance.
In adults, pulmonary vascular resistance is usually low and systemic high.
- Why do fetus’s have high vascular resistance in pulmonary circulation?
- Vasoconstriction is response to low PO2’s
- Fluid filled lungs pressing on vasculature
Fetal Circulation:
- What are SaO2 saturations throughout normal fetal circulation?
- What SaO2 is blood throughout fetal circulation from umbilical vein to mom and back to the placenta?
Umbilical vein = SaO2 80%
Right Atrium (RA) = 40%
Left Ventricle (LV) = 65%
what does the placenta develop from?
The Chorionic villi
- where gas exchange occurs
- Turns into the embryonic blastocyst
- The blastocyte expands and grows into the placenta
what are the parts make up the chorionic villi?
- The maternal compartment
- The fetal compartment
What is the function of the Chorionic Villi?
Site of maternal and fetal passive exchange of nutrients and waste.
- A structural anchor
- exchange of gases, nutrients, & metabolic wastes
What are some precautions for the mother that involve the Chorionic Villi/Placenta?
Toxic substances (alcohol, nicotine, opiates, cocaine, caffeine) and some infectious organisms (rubella) and viruses (HIV) can pass to the fetus
Describe the role of the Umbilical Vein in fetal circulation
Returns oxygenated blood from the placenta.
- Enters the fetal body through the umbilicus
- Connects to fetal circulation under the liver
- Diverts with 50% of blood going through liver, the rest diverting to become the ductus venosus
Describe the role of the Ductus Venosus in fetal circulation
- Shunt that allows about 50% of blood returning from placenta
- Drains into the inferior vena cava, then the right atrium