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Y2 LCRS 1 - RDA > Foetal growth > Flashcards

Foetal growth Flashcards

1
Q

What is foetal growth?

A

The increase in mass (and length) that occurs between the end of the embryonic period and birth

  • compared against normal - data obtained from miscarriage samples
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2
Q

What are the phases of normal fetal growth?

A
  1. Cellular Hyperplasia - The first stage takes place during 4–20 weeks of gestation, rapid cell division and multiplication (hyperplasia) occurs as the embryo grows into a fetus.
  2. Hyperplasia and hypertrophy - The second stage, 20–28 weeks of gestation, cell division declines and the cells increase in size.
  3. Hypertrophy alone - The third stage, 28–40 weeks, there is rapid increase in cell size, rapid accumulation of fat, muscle, and connective tissue.
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3
Q

What factors influence foetal growth?

A
  1. Substrate supply
    • sufficient nutrients are essential to achieve genetic potential
    • primarily based on placenta which is dependent upon both uterine and placental vascularity
  2. Maternal factors
    • mother’s age
    • drug use, alcohoL, smoking + nicotine
    • physical health, diseases (hypertension, diabetes, coagulopathy), prenatal depression
    • diet
    • environmental toxins
    • poverty
  3. Foeto-placental factors
    • Previous pregnancies
    • Genetic potential - derived from both parents

and mediated through growth factors eg insulin like growth factors

* Gender (B\>G)
* Hormones
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4
Q

Give examples of foetal hormones (under foeto-placental factors) that affect foetal growth.

A

In particular,

  • Insulin
  • Glucocorticoid
  • Thyroxine - esp 3rd TM for CNS development (remember cretinism for low iodine ? Mental retardation)
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5
Q

What are the limitations of centile charts in the assessment of foetal growth?

A
  • Maternal weight, height ethnic background, previous pregnancies affect foetal growth
  • Must allow for this when looking at charts
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6
Q

How is symphysis fundal height measured? What are the limitations?

A

Distance between pubic symphysis and top of uterus

Smaller: wrong dates, small for gestational age, oligohydramnios, transverse lie

Larger: wrong dates, molar pregnancy, multiple gestation, large for gestational age, Polyhydramnios, Maternal obesity, Fibroids

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7
Q

What are the pros and cons of SFH?

A
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8
Q

What is the importance of correct dating? Give both obsolete and current methods of dating.

A

Importance of correct dating: Small for Gestational Age or Large for Gestational Age confusion, Inappropriate inductions, Steroids in preterm delivery (NOTE: given to speed up surfactant production in fetus > prevent from preterm infant respiratory distress syndrome)

Obsolete: Dating by LMP since it is inaccurate (irregular periods; abnormal bleeding; oral contraceptives, breastfeeding)

Current:

  1. All pregnancies should be dated by Crown-rump length (top to bottom) except IVF pregnancies
  2. Head circumference is used if first scan is done after 14 weeks (CRL>84mm)
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9
Q

What are some techniques used in ultrasound monitoring of fetal growth?

A
  • Fetal growth is assessed by 4 biometrical parameters (Biparietal diameter , head circumference, abdominal circumference, femur length) and their combination (Estimated Fetal Weight)
  • Normaltive growth curves constructed from ultrasound measurements are expressed in centiles
  • They are used clinically to identify a normal intrauterine growth and detect risk of obstetric and neonatal complications
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10
Q

What are the by three underlying principles of customised standard that defines the individual fetal growth potential?

A
  1. Adjusted to reflect maternal constitutional variation maternal ht, wt, ethnicity, parity
  2. Optimised by presenting a standard free from pathological factors such as diabetes and smoking
  3. Based on fetal weight curves derived from normal pregnancies
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11
Q

What are the implications of Obstetric Ultrasound Examination?

A
  • Assessment of fetal “wellness” not just size
  • Looking at trends in growth
  • Predicting fetal metabolic compromise
  • Anticipating the need to deliver prematurely
  • Liaising with Neonatal Services
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12
Q

Why is ultrasound the preferred imaging choice for assessment of foetal growth?

A
  • Safe for mother and baby - Painless
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13
Q

Define the following:-

  • SGA
  • FGR
A
  • SGA = Small for gestational age = defined as a weight below the 10th percentile for the gestational age - newborns are those who are smaller in size than normal for the gestational age
  • FGR = Fetal growth restriction = Failure of the fetus to achieve its predetermined growth potential for various reasons (aka IUGR)
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14
Q

What are the implications of low birth weight?

A
  • Many FGR babies are delivered prematurely
  • 3-10 fold increase in prenatal mortality short- and long-term morbidity
  • LBW, FGR and preterm delivery are closely associated pathologies
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15
Q

Why is the tenth centile chosen to foetal growth restriction?

A
  • When choosing which centile to use, a balance between sensitivity and specificity is being made – the tenth centile is most sensitive and the third centile is most specific.
  • The tenth centile will capture all babies with FGR, but will also include those babies that are just small for gestational age, i.e. you get a number of false positives.
  • All babies recorded using the third centile will have FGR, but some FGR babies may be missed, i.e you get a number of false negatives.
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16
Q

When should the term FGR be used?

A
  • The term FGR should only be used for fetuses with definite evidence that growth has altered.
  • Growth is a dynamic process of a change of size over time and, therefore, it can only be assessed by serial observation.
17
Q

What are the short and long term sequelae of FGR (IUGR/LBW/ Prematurity)?

A
  • The most common factor identified in stillborn babies.
  • In addition, it has serious consequences for babies who survive (figure)
  • Furthermore, there is an increased risk of FGR and intrauterine death (IUD) in mother’s subsequent pregnancy.
18
Q

How is IUGR screened and detected?

A
  • Usually ultrasound - Serial assessments of biparietal diameter, head circumference, abdominal circumference and femur length - Serial estimates of foetal size parameters - Evidence of foetal compromise on cardiotocography or abnormal Dopplers or evidence of maternal compromise
19
Q

How is IUGR managed?

A
  1. Timing delivery in these pregnancies depends on balancing risks to foetus if it remains in utero and hazards from prematurity, which decrease as gestation advances 2. Corticosteroids should be administered (if not already given) at gestations < 36 weeks in order to improve neonatal wellbeing, notably lung development 3. In some pregnancies, health of mother or infant (or both) can deteriorate rapidly, making an emergency Caesarean section a necessity
20
Q

What are the practical causes and aetiologies of FGR/SGA?

A
21
Q

What are the purposes of the first and second halves of pregnancy?

A
  • The first half of pregnancy is a time of preparation for the demands of rapid fetal growth in the second half
  • Alterations in maternal physiology facilitate transfer of nutrients to the fetus
22
Q

What is the main factor influencing fetal growth in the second half of pregnancy?

A

Placental function

23
Q

When does placentation take place?

A
  • 7–8 days after fertilization
24
Q

What are the functions of the placenta?

A
  1. Separation
    • prevents mixing of maternal and foetal blood despite the close contact between the tissues
  2. Exchange of nutrients (maternal to fetal) and waste products (fetal to maternal)
  3. Biosynthesis
    • Hormones and Growth factors are actively produced
    • Functions as a “transient hypothalamo-pituitary-gonadal axis
  4. Immunoregulation
    • ensures that there is no rejection of the conceptus
    • placenta (rather than the uterus) is the key tissue → occasional survival of ectopic pregnancy until delivery shows that the uterine lining is not completely essential for pregnancy
  5. Connection (or anchorage)
    • placenta makes strong connections with the underlying maternal decidua to last for the 9 months of pregnancy.
    • anchorage is essential as the placenta is in contact with maternal arterial blood
25
Q

How does the mother increase the supply of low pressure blood to the foetus?

A

SPIRAL ARTERY REMODELLING

NOTE: blood supply via spiral arteries, uterine arteries, arcuate arteries

How do these structure develop = MAIN CHANGES WITH SPIRAL ARTERIES BY TROPHOBLASTS FROM THE PLACENTA

  1. Spiral arteries open to form funnel shaped openings to allow trophoblast entry
  2. Endometrium undergoes decidualisation (mediate the invasiveness of trophoblast cells and triggers remodelling of spiral arteries)
  3. Cytotrophoblasts
    • invade spiral arteries (same molecular mechanisms as tumors, but are highly regulated and controlled)
    • remodel:
      • (1) destroy the smooth muscle and elastic layers and replace them with fibrinoid material → no longer vasoconstricts → narrow vessels widen to carry more blood to placenta
      • (2) line vessels with trophoblast
  4. Cytotrophoblast plug gradually breaks down to expose placenta to maternal blood → haemotrophic nutrition (end of 1st trimester)
26
Q

What are the 2 phases of spiral artery remodelling?

A

Happens in 2 waves

1st

  • When = time of primary implantation in early pregnancy and lasts for several weeks
  • Reaches the decidual (originally endometrial) layer of the spiral arteries

2nd

  • When = 14–16 weeks of gestation and is completed in 4 weeks
  • Extends to myometrial layer (much greater depth)
27
Q

Contrast the structure of the spiral artery between non-pregnant, normal pregnancy and pathological condition.

A
  1. Spiral arteries in non-pregnant within + blood supply to endometrium
  2. Normal pregnancy
    • Spiral arteries open to form funnel shaped openings to allow trophoblast invasion
    • Invasion depth up to myometrium
  3. Pre-eclampsia
    • Spiral arteries do not open properly
    • Invasion depth up to decidua
    • 30–50% of the spiral arteries of the placental X undergo remodeling
    • Poor placental perfusion
    • Vessel contraction
28
Q

What is the clinical definition of pre-eclampsia?

A
  • Multisystem disease that usually manifests as hypertension and proteinuria
    • BP>140/90mmHg and proteinuria >0.3g/24hour (PCR>30).
    • Mild140-149/90-99mmHg
    • Moderate 150-159/100-109mmHg
    • Severe ≥160/110mmHg
  • arising de novo
  • after the 20th week of gestation in a previously normotensive woman and resolving completely by the 6th postpartum week
29
Q

Describe the pathophysiology of pre-eclampsia.

A

Causes

  • Impaired trophoblast differentiation
  • Spiral arteries do not open properly > impaired trophoblast invasion
  • Placenta does not embed properly

Results

  • Limited invasion of spiral arteries to decidua (X myometrium)
  • 30–50% of the spiral arteries of the placental X undergo remodeling

Compensation to HIGH BP

  • Poorly perfused placenta > reduction in blood flow to the intervillous space + placental hypoxia and ischaemia X meet the needs of the foetus
  • Compensate by raising maternal blood pressure to increase flow through the placental system
30
Q

Which fetuses need growth monitoring?

A

Bad Obstetric History

  • Previous maternal hypertension
  • Previous FGR
  • Stillbirth
  • Placental Abruption

Concerns in index pregnancy

  • Abnormal serum biochemistry PAPP-A <0.3 MoM
  • Reduced symphysis fundal height
  • Maternal systemic disease e.g. hypertension, renal, coagulation
  • Antepartum haemorrhage
31
Q

How can we predict which fetuses become growth restricted ?

A

Maternal history - risk factors

  • Poor Obstetric History
  • Primips
  • Obese
  • Afro-Carribean / African
  • Strong Family History
  • Essential hypertension
  • Diabetes / Impaired Glucose Tolerance
  • Systemic vascular disease
  • Renal disease
  • Thrombophilias
32
Q

What are the events from FGR leading up to IUD?

A
33
Q

What are the results of foetal hypoxia?

A

Mainly reduced movements - to conserve energy

34
Q

How can foetal hypoxia be detected?

A

Measured flow in:

  • Middle cerebral artery
  • Umbilical artery
  • Ductus venosus

Fetal movement countings:

  • A reduction in fetal movements may precede fetal death by a day or more; therefore, fetal movement counting may be of value in assessing fetal wellbeing.
  • Cardiff kick chart is the most commonly used method.
  • Women who report a reduction in fetal movements, and particularly those who report an absence of fetal movements, need cardiotocography and/or an ultrasound assessment of the fetus to reassure the mother and ensure fetal wellbeing.
35
Q

What are the general principles of management of FGR pregnancies?

A
  1. Problems in the index pregnancy: Manage according to serial fetal biometry, fetal Doppler, BPP and CTG
  2. Screening of “at risk” pregnancies: 24/40 Ut A screening
  3. Delivery: Aim to deliver when ≥28 weeks and / or ≥500g, Caesarean section for compromised fetuses
36
Q

How are deliveries managed with pregnancies complicated by FGR?

A
  1. Timing delivery in these pregnancies depends on balancing the risks to the fetus if it remains in utero and the hazards from the prematurity, which decrease as the gestation advances
    • Evidence of fetal compromise on CTGs or abnormal Dopplers/ ultrasound finding / maternal compromise
  2. Corticosteriods should be administered (if not already given) at gestations < 36 weeks in order to improve neonatal wellbeing
  3. The mode of delivery will depend upon:
    • Gestation of the pregnancy
    • Condition of the pregnancy
    • State of the cervix
    • Presentation of the fetus
    • Other factors: oligohydramnios - labour may be poorly tolerated due to cord compression
37
Q

Contrast between the incidence, causes, and managment of early and late IUGR.

A
38
Q

Describe the foetal circulation.

A

Y2 LCRS 1 - RDA (11 decks)

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