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Reproductive System > 9 > Flashcards

9 Flashcards

1
Q

How does gas exchange occur at the placenta?

A
  • diffusion barrier: shall, and decreases as pregnancy proceeds
  • fetal blood has lower partial pressure of O2 to allow a gradient transfer from mother to fetus
  • maternal pO2 increases only marginally
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2
Q

How can a pregnant woman develop a physiological respiratory alkalosis?

A

-progesterone causes physiological hyperventilation

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3
Q

Even though fetal blood has low pO2, what factors increase the O2 content?

A
  • fetal Haemoglobin variant

- fetal haematocrit is increased over that in the adult

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4
Q

What factors promote O2 exchange to the fetus at the placenta?

A

increased maternal production of 2,3 DPG

  • secondary to physiological respiratory alkalosis of pregnancy
  • normally the curve is shifted to left, but with 2,3 BPG the curve is shifted back to right to reduce Hb maternal affinity for O2

Double Bohr effect

  • Mother: as CO2 goes into intervillous blood, pH decreases causing a decreased maternal affinity for O2
  • Fetus: fetus is giving up CO2 due to gradient which increases pH and results in increased affinity for O2
Fetal Hb
-HbF is predominant by week 12
-2 alpha and 2 gamma subunits
-has greater affinity for O2 because it doesnt bind to 2,3 BPG as effectively as maternal Hb
See REPRO fetal phys slide 8-10
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5
Q

Explain the CO2 transfer between mother and fetus

A
  • progesterone-driven hyperventilation
  • thus lower pCO2 in maternal blood
  • creates a concentration gradient
  • double Haldane effect occurs
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6
Q

What is the Haldane effect?

A
  • double effect
  • mother: maternal Hb gives up O2, it can accept increasing amounts of CO2
  • fetus: fetal Hb gives up more CO2 as O2 is accepted
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7
Q

What is fetal distress?

A
  • fetal response to hypoxia
  • bradycardia occurs via vagal stimulation to try and reduce the O2 demand required by heart
  • smoking can cause chronic hypoxaemia
  • can eventually lead to intrauterine growth restriction
  • HbF and increased [Hb]
  • priority of flow to brain and heart
  • fetal chemoreceptors detecting decreased pO2 or increased pCO2

See REPRO fetal phys slide 20

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8
Q

Explain fetal circulation

A
  • receives oxygenated blood from mother via placenta in umbilical vein
  • lungs are non-functional
  • bypasses the lungs
  • returns to placenta via umbilical arteries
  • occurs through shunts
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9
Q

List and describe the shunts in fetal circulation

A

Ductus venosus

  • only small amount of blood enters liver because liver is massive and could engulf entire fetal circulation
  • ductus venosus allows blood from umbilical vein to shunt directly to IVC
  • shunting blood away from liver maintains high level of O2 in the circulation that goes to brain and rest of body

Foramen ovale

  • allows most of blood to go from RA to LA
  • occurs due to the higher pressure in RA than LA
  • at birth pressure reverses and ovale closes
  • only small amount of deoxygenated blood returns to LA which allows O2 saturation to be high

Ductus arteriosus

  • small amount of blood enters right ventricle due to the CRISTA DIVIDENS
  • ensures that RV doesnt atrophy through disuse and allows small amount of blood to travel to lungs to promote its development
  • connects pulmonary trunk to aorta

See REPRO fetal phys slide 14-19

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10
Q

What are the hormones necessary for fetal growth?

A
  • insulin
  • IGF1 and IGF2
  • IGF2 nutrient independent, dominant in first trimester
  • IGF2 nutrient DEPENDENT, dominates in T2 and T3
  • Leptin: placental production
  • plus EGF, TGFa
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11
Q

Explain the effect of nutrition on fetal growth during pregnancy

A
  • Week 0-20 (T1): hyperplasia of cells
  • Weeks 20-28 (T2): Mix of hyperplasia and hypertrophy of cells that have developed
  • Week 28term (T3): predominantly hypertrophy
  • Malnutriton can cause symmetrical or asymmetrical growth
  • nutritional hormonal status during fetal life can influence health in later life

See REPRO fetal phys slide 22

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12
Q

What is the difference between symmetrical and asymmetrical growth restriction?

A
  • symmetrical: all parts of the fetus are small

- asymmetrical: “head sparing” aka restriction on abd but it is disproportionately smaller than the head

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13
Q

What is amniotic fluid?

A
  • fluid that fills amniotic sac which surround fetus during pregnancy
  • function: protection and contains substances critical for lung development
  • volume is proportional to the size of the fetus
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14
Q

How is amniotic fluid produced?

A
  • composed of fetal urine
  • production of urine starts around 9 weeks
  • up to 800ml/day in T3
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15
Q

How is amniotic fluid recycled?

A
  • inhale fluid by fetus practicing breathing movement
  • helps with production of lung especially surfactant
  • fetus can also swallow fluid so it goes to GI tract
  • eventually becomes meconium

See REPRO fetal phys slide 24

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16
Q

What is the composition of amniotic fluid?

A
  • 98% water
  • electrolytes, creatinine, urea, bile pigments, renin, glucose, hormones and fetal cells, lanugo, and vernix caseous

See REPRO fetal phys slide 25

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17
Q

What is lanugo?

A

-fine hair covering fetus

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18
Q

WHat is vernix caseosa?

A

-waxy substance that covers fetus

19
Q

What is meconium?

A
  • debris from amniotic fluid plus intestinal secretions including bile
  • it should only be released from fetus after delivery
  • if fetus is in distress one clinical sign is meconium staining
20
Q

What is amniocentesis?

A
  • sampling of amniotic fluid
  • allows for collection of fetal cells
  • useful diagnostic test (ex. Fetal karyotyping)
  • can be used for D
  • invasive and does carry risk of miscarriage
21
Q

Explain physiological jaundice in a fetus

A

-common in newborns
-during gestation, clearance of bilirubin is handled by placenta
-because delay in newborn’s ability to conjugate and excrete bilirubin
-jaundice should disappear within 24 hours
-otherwise it is pathological
See REPRO fetal phys slide 27

22
Q

Describe the fetal period

A
  • longest period of development
  • 9 weeks to term
  • term of physiological maturation of structures and growth

See REPRO fetal g&d slide 3-4

23
Q

Describe the pattern of weight gain during the fetal period

A
  • main tissue contributing to weight at first is protein because of muscle development
  • later on in fetal period, adipose tissue is developed for metabolic purposes and for regulation of heat

See REPRO fetal g&d slide 5-6

24
Q

Describe the proportion of growth during the fetal period

A
  • at 9 weeks, 50% of length of fetus is head
  • as pregnancy proceeds, limbs and trunk elongate so body proportions change

See REPRO fetal g&d slide 7-8

25
Q

What are the main things for the ante-natal assessment of fetal well-being

A

Ask mom

  • fetal movements (occurs around 20 weeks
  • mom is aware and sensitive of movements

Regular measurements of uterine expansion

  • Symphysis-fundal height
  • non-invasive way to assess growth by measuring length from pubic symphysis to top of fundus of uterus
  • at 20 weeks SFH should be roughly at umbilicus
  • thereafter, it should fought equal the week of pregnancy (28cm = 28 weeks)

Ultrasound scan (USS)

  • safe
  • can be used early in pregnancy to calculate age and to rule out ectopic or number of fetuses
  • usually carried out at ~20 weeks because structures have developed and big enough to be seen
  • in order to assess fetal growth and fetal anomalies

See Wkbook and REPRO fetal g&d slide 9-10

26
Q

How can you estimate fetal age?

A

LMP (last menstrual period)

  • but prone to inaccuracy
  • pregnancy happens roughly two weeks after LMP

Developmental Criteria

  • allows accurate estimation of fetal age
  • done by comparing USS measurements of fetus to an average value
27
Q

What is Crown Rump Length (CRL)?

A
  • measurement of dating pregnancy between 7-13 weeks
  • due to the linear nature of its progression
  • used to estimate EDD
  • scan in T1 also used to check location, number, viability
  • length of fetus from head to tail

See REPRO fetal g&d slide 12

28
Q

What is biparietal diameter?

A
  • the distance between the parietal bones of the fetal skull

- used in combination with other measurements to date pregnancies in t2 and T3

29
Q

What is abd circumference and femur length?

A
  • these measurements are used in combination with biparietal diameter during T2 and T3 (when abd is widest)
  • used for dating and growth monitoring
  • also useful for anomaly detection
  • must look at structures to ensure they’re developing normally such as heart and neural tube
30
Q

What are 3-D or 4-D USS?

A
  • new wave of obstetric ultrasonography
  • doesnt replace standard USS as of yet

See REPRO fetal g&d slide 15

31
Q

Explain the classification of birth weights (i.e. normal, too big, too small etc.)

A
  • 3500g is NORMAL
  • <2500g suggests growth restriction
  • > 4500g is macrosomia (maternal diabetes)
  • many factors influence birth weight such as if mother is petite, baby will be petite
32
Q

What are some reasons for low birth weight?

A
  • premature
  • could be petite since mom is petite
  • may have growth restriction (associated with neonatal morbidity and mortality)
33
Q

How is the respiratory system developed in the fetus?

A
  • lungs develop relatively late
  • lungs develop as an outouching of foregut to create the bronchopulmonary tree during embryonic period
  • budding and branching of bronchioles starts in week 8-16 (pseudoglandular stage)
  • further branching happens to form respiratory bronchioles in weeks 16-26 (canicular stage)
  • alveoli develop from ends of respiratory bronchioles at weeks 26 to term
  • only then doe Type 1 and 2 pneumocytes develop in order to produce surfactant

See REPRO fetal g&d (slide 19-23)

34
Q

What determines fetal “viability”?

A
  • whether pneumocytes are present or not

- otherwise gas exchange cant occur

35
Q

What happens to the lungs during T2 and T3?

A
  • gas exchange conducted at placenta but lungs must be prepared to assume full burden at birth; they need to practice
  • “breathing” movements allows respiratory muscles to work and practice
  • conditions of the respiratory musculature
  • fluid filled
  • crucial for normal lung development
  • ensures that baby take in amniotic fluid into lungs
  • allows to drive the development for the lungs
36
Q

What is respiratory distress syndrome?

A
  • often affects infants born pre-maturely
  • insufficient surfactant production
  • if pre-term delivery is unavoidable or inevitable
  • then glucocorticoid treatment (of the mother)
  • increases surfactant production in fetus
37
Q

How is the CVS system developed in the fetus?

A
  • fetus CVS system is arranged to ensure oxygenated blood is collected by umbilical vein at the placenta and is circulated around fetus
  • average fetal HR is 110-160 bpm
  • HR is acheived around 15 weeks
  • must know in order to assess fetal bradycardia as a sign of fetal distress
38
Q

How does the urinary system develop in the fetus?

A
  • fetal kidney function begins in week 10
  • fetal urine majorly contributes to amniotic fluid
  • fetal kidney function isnt necessary for survival in utero but without it oligohydramnios can occur
  • largely reliant on maternal renal function for excretion
39
Q

What is oligohydramnios and polyhydroamnios?

A

Oligohydramnios

  • too little amniotic fluid
  • may be due to placental insufficiency
  • can indicate poor renal function in the fetus

Polyhydramnios

  • too much amniotic fluid
  • indication of issue in recycling amniotic fluid
  • such as problem in swallowing (CNS defect) or congenital abnormalities (eg. Trachea-oesophageal fistula)
40
Q

How does the nervous system develop in the fetus?

A

-first to start developing and last fo finish
-so it is most vulnerable to injury
-coordinated voluntary movements require the CORTICOSPINAL tract which begins to form in the 4th month
-only myelination of brain occurs at 9th month
See REPRO fetal g&d (slide 30)

41
Q

How do the sensory and motor systems develop in the fetus?

A
  • no movement until 8th week
  • thereafter a large number of movements occur
  • these all happen to “practice” for life after birth (ex. Suckling, breathing)
  • baby is “rehearsing” movements in utero so that it is prepared to do it immediately after birth

See REPRO fetal g&d slide 31

42
Q

What is “quickening” in regards to the fetus?

A
  • maternal awareness of fetal movements from 17 weeks onwards
  • low cost, simple method of ante-part I’m fetal surveillance
  • reveal those fetuses requiring follow-up
43
Q

Describe the development of the lungs and brain in the fetus

A

See REPRO fetal g&d slide 33

44
Q

Why might the symphysis-fundal height not correlate to the week of gestation?

A

-due to polyhydramnios or oligohydramnios

Reproductive System (11 decks)

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