Preparation for birth & delivery

Question 1

how do we assess interuterine growth?

Answer 1

post birth - birth weigh is a good proxy

before - its difficult

Maternal weight gain, uterine fundal height and maternal abdominal girth are still used in resource-poor situations but have a low predictive value for complications of pregnancy.

Ultrasound provides more accurate estimates, and biparietal diameter, crown-rump length, femur length and abdominal diameter are routinely measured.

Question 2

how do we date pregnancies?

why is it important?

Answer 2

Obstetricians date a pregnancy from the first day of the last menstrual period (LMP), as this is usually known, unlike the date of ovulation. Pregnancy or gestational dates are therefore 14 days in advance of the dates post-fertilization or post-conception used by embryologists.

used to monitor growth rate - important§

Question 3

is absolute birth weight a good parameter?

list some better ones

Answer 3

low birthweight being defined as <2.5kg and high birthweight or macrosomia being >4kg.

but this depends on many factors

Now use centile charts, with small for gestational age (SGA) being below the 10th centile, and large for gestational age (LGA) above the 90th centile

take into account ethniciity, BMI, and other factors

Question 4

Fetuses that are growth restricted due to lack of oxygen or nutrients usually show what signs

Answer 4

Fetuses that are growth restricted due to lack of oxygen or nutrients usually show brain-sparing,

in that blood is directed to the brain at the expense of peripheral tissues.

Hence, head circumference continues to enlarge, whereas abdominal circumference reflecting development of the liver lags behind.

Question 5

what is meant by asymmetric growth,

Answer 5

Hence, head circumference continues to enlarge, whereas abdominal circumference reflecting development of the liver lags behind.

This is referred to as asymmetric growth, and the increase in blood flow to the brain can be detected by Doppler ultrasound assessment of middle cerebral artery flow.

Question 6

give some maternal factors which affect fetal growth?

Answer 6

• Uterine size.
• nutrition
• Parity
• socio-economic background + other environment factors
• Diseases
• envirionmental factors

Question 7

describe how the uterine size of the mother can affect fetal growth

Answer 7

big uterus = more growth

this is still observed after birth.

eg - shire and shetland ponies.

Human fetuses in multiple pregnancies tend to show growth retardation when total fetal weight is about 3.2kg, which occurs at week 30 with twins and week 26 with quads.

Question 8

describe how nutrition can affect a fetus growth

Answer 8

worldwide maternal undernutrition is the commonest cause of fetal growth restriction (FGR).

in developed world - its normally resttricted blood to placenta that causes FGR.

In the developed world, more and more women enter into pregnancy obese due to increased intake of a ‘Western- style’ diet that is high in sugar and fat. Maternal obesity and obesogenic diets also have impacts on fetal growth and pregnancy outcome, with those women at greater risk of preeclampsia and gestational diabetes and delivering FGR and large for gestational age/macrosomic babies.

Question 9

describe how Parity can affect baby growth

Answer 9

On average, first babies are smaller than subsequent babies.

Expansion of the uterus and remodelling of the maternal vessels together with the maternal physiological adaptations occurs more readily in subsequent pregnancies.

Question 10

describe how Socio-economic and other environmental factors can impact fetal growth

Answer 10

Low birthweight is correlated with low socio-economic status of the mother

may ge generational

Smoking and drug abuse reduce fetal growth by up to 300g in a dose-dependent fashion.

Similarly, teenage mothers give birth to smaller babies because they often are still growing themselves and apportion available nutrients less readily to the fetus.

Question 11

describe how Diseases can affect fetal growth

Answer 11

Maternal cardiovascular diseases, such as hypertension, reduce birth weight, possibly due to reduced maternal blood flow in the placental intervillous space.

In contrast, poorly controlled diabetes leads to increased birth weight due to fetal hyperglycaemia and hyperinsulinaemia.

Question 12

effect of hypertension on birthweight?

Answer 12

hypertension, reduce birth weight, possibly due to reduced maternal blood flow in the placental intervillous space.

Question 13

effect of poorly controlled diabetes on bith weight?

Answer 13

In contrast, poorly controlled diabetes leads to increased birth weight due to fetal hyperglycaemia and hyperinsulinaemia.

Question 14

Environmental factors - how they affect fetal growth

Answer 14

The hypobaric hypoxia associated with pregnancy at high altitude is associated with a reduction in birthweight of 100g per 1,000m of ascent.

Indigenous populations are relatively protected due to adaptive mutations that increase blood flow to the uterus.

Question 15

_____ ______ is the major cause of FGR in developed countries.

Answer 15

Placental insufficiency is the major cause of FGR in developed countries.

Question 16

placental insufficiency is commonly associated with?

Answer 16

commonly associated with deficient remodelling of the maternal spiral arteries, leading to malperfusion of the placenta.

Question 17

how can we clinically assess the placental function

Answer 17

assessed clinically by Doppler ultrasound assessment of the waveform in the uterine artery at the point where it crosses the internal iliac artery (standardized location). High resistance is associated with FGR and pre-eclampsia.

(might look for reduced diastolic flow - showing poor spiral artery remoddeling)

Question 18

problems with malperfusion of the placenta?

Answer 18

Malperfusion causes infarction of the placenta and loss of surface area for exchange.

Question 19

T or f

Severe placental pathology affects the waveform in the umbilical arteries

Answer 19

T

Question 20

High placental resistance, as indicated by ………………whihc facotrs? ……… is associated with which conditions?

Answer 20

High placental resistance, as indicated by

• absent or reversed end-diastolic flow

is associated with

1. FGR,
2. fetal hypoxaemia
3. and impending stillbirth

Question 21

Compromise of barrier function may lead to what for the fetus/

Answer 21

Compromise of barrier function may lead to excessive levels of maternal cortisol or xenobiotics crossing the placenta, and influencing fetal growth.

Question 22

The drive to fetal growth is provided primarily by ….

Answer 22

The drive to fetal growth is provided primarily by the genes the fetus inherits.

Question 23

give 4 fetal factors influencing growth

Answer 23

• fetal sex
• fetal genome
• infection
• Endocrine factors

Question 24

describe how fetal sex can influence fetal growth

Answer 24

In all ethnic groups, male neonates are significantly heavier, longer and have a larger head circumference than females.

Question 25

describe how the fetal genome can influence fetal growth

Answer 25

Specific gene defects also alter intrauterine growth, but account for \<10% of cases of FGR.

Question 26

describe how fetal infection can affect fetal growth

Answer 26

Toxoplasmosis, rubella, cytomegalovirus, and herpes (TORCH) can all cause FGR. As they usually occur in the first trimester they cause symmetric growth reduction, and account for \<10% of cases.

Question 27

describ how fetal derived endocrine factors can affect fetal growth

Answer 27

Maternal hormones such as insulin and TSH do not cross the placenta, and fetal growth is driven by its own endocrine environment. The IGF family, IGF-I and IGF-II, is a powerful regulator of fetal growth, as evidenced by disorders of imprinting. Fetal insulin may be important in late pregnancy, and high levels are associated with increased glucose uptake and body weight.

Question 28

describe the role fetal IGF plays in fetal growth

Answer 28

The IGF family, IGF-I and IGF-II, is a powerful regulator of fetal growth, as evidenced by disorders of imprinting. IGF-II is normally only expressed from the paternal allele, but uniparental disomy or loss of imprinting control can lead to a double dose of IGF and the hypertrophic **Beckwith- Wiedemann syndrome.** Levels of IGF-I in the fetus are responsive to oxygen and nutrient availability, and correlate with birthweight. IGF activity is regulated by gene expression and also through the family of IGF-binding proteins.

Question 29

describe Beckwith- Wiedemann syndrome.

Answer 29

IGF-II is normally only expressed from the paternal allele, but uniparental disomy or loss of imprinting control can lead to a double dose of IGF and the hypertrophic Beckwith- Wiedemann syndrome.

Question 30

Levels of IGF-I in the fetus are responsive to oxygen and nutrient availability, and correlate with \_\_\_\_\_\_\_\_

Answer 30

Levels of IGF-I in the fetus are responsive to oxygen and nutrient availability, and correlate with birthweight.

Question 31

Both SGA and LGA babies are at risk of increased neonatal morbidity and mortality; why?

Answer 31

Both SGA and LGA babies are at risk of increased neonatal morbidity and mortality; SGA: because of poor organ development and compromised nutritional reserves, LGA: because of difficulties in passing through the birth canal (obstructed labour).

Question 32

T or f? ## Footnote Longer term, adults that were born growth restricted are at increased risk of chronic diseases, such as cardiovascular disease, type 2 diabetes, obesity and some cancers.

Answer 32

T shows that intrauterine growth can affect adult life for years to come

Question 33

6 ways fetal circulation differs from adult?

Answer 33

1. supplies the placenta 2. mainly bypasses lungs 3. 2 shunts: foramen ovale and ductus arteriosus for pulmonary bypass 4. Right ventricular output is higher than left due to the shunts. 5. Total cardiac output (both ventricles) is about 4 fold higher than in the adult. 6. Oxygenated blood coming from the placenta by-passes the liver by the ductus venosus (DA)

Question 34

\_\_\_\_% of the combined fetal cardiac output goes to the placenta which has a low resistance.

Answer 34

**40-50%** of the combined cardiac output goes to the placenta which has a low resistance.

Question 35

Total peripheral resistance and blood pressure are ______ in fetuses than adults.

Answer 35

Total peripheral resistance and blood pressure are **lower** in fetuses than adults.

Question 36

Pulmonary vascular resistance is _____ in utero.

Answer 36

Pulmonary vascular resistance is **high** in utero.

Question 37

the foramen ovale does what?

Answer 37

shunts blood from the right atrium to the left atrium

Question 38

the ductus arteriosus does what?

Answer 38

shunts blood form pumlmonary atery to the aorta

Question 39

the ductus venosus does what?

Answer 39

allows the umbilical vein to bypass the liver

Question 40

fetal or adult? the heart chambers beat in parallel

Answer 40

fetus

Question 41

how does the fetus ensure the brain gets most of the oxygen delivered?

Answer 41

Preferential streaming of flow from the DA in the inferior vena cava to the FO ensures blood with the highest saturation is delivered to the brain Only after this point, will the blood mix with blood from the right ventricle through the pulmonary artery and the DA to supply the rest of the body

Question 42

does the ductus arteriosus enter the aorta after the Brachiocephalic artery has branched?

Answer 42

yes

Question 43

how is fetal haemoglobin asapted for its purpose?

Answer 43

fetal Hb has a reduced affinity for 2,3DPG, which increases O2 binding. The concentration of 2,3DPG is also lower in fetal than maternal erythrocytes. Oxygen uptake across the placenta is facilitated by the double Bohr shift which helps to maintain the diffusion gradient across the placenta but the most important thing about the increased affinity is the **higher oxygen content of blood at a relatively low pO2.**

Question 44

this is importnat: ## Footnote most important thing about the increased affinity is the higher oxygen content of blood at a relatively low pO2.

Answer 44

Yes

Question 45

describe the fetal double bohr effect

Answer 45

Question 46

when does fetal alveolar developement occur?

Answer 46

Alveolar development only occurs in the last few weeks of gestation, and continues after birth.

Question 47

The respiratory epithelium differentiates into which types of cells?

Answer 47

The respiratory epithelium differentiates into type I and type II pneumocytes.

Question 48

which pneumocytes secrete surfactant?

Answer 48

Type 2

Question 49

effect of surfactant?

Answer 49

reduces surface tension effects.

Question 50

problems in the lungs of premature babies? how can it be treeated?

Answer 50

Hence, premature babies suffer severe respiratory distress. An artificial surfactant is now available that can be introduced into the bronchi, but can also give the mother a high dose of synthetic glucocorticoids 24 hrs before having to do a premature delivery in order to stimulate lung maturation. The influence of cortisol on surfactant production is shown in sheep models where cortisol treatment in one twin increases surfactant production

Question 51

Fetal breathing movements can be detected from around ____ weeks of gestation

Answer 51

Fetal breathing movements can be detected from around 10 weeks of gestation

Question 52

describe mechanostimulation for lung developement

Answer 52

al breathing movements can be detected from around 10 weeks of gestation, and provide important mechano-stimulation for alveolar development and surfactant release.

Question 53

Babies with congenital diaphragmatic hernia suffer from.....

Answer 53

Babies with congenital diaphragmatic hernia suffer from **hypoplastic lungs.** Attempts have been made to rectify the defect in utero to preserve lung development.

Question 54

where does the amniotic fluid come from?

Answer 54

The lungs secrete fluid which contributes to the overall amniotic fluid volume, but the main contributor comes from the kidneys – a hypotonic urine as the Loops of Henle are not well developed. There is also fetal swallowing of amniotic fluid, and so a constant turnover.

Question 55

what is oligohydramnios.

Answer 55

Fetal stress is associated with reduced fluid volumes – oligohydramnios.

Question 56

In all species studied to date, there is an increase in ___________ concentration in the fetal circulation towards term

Answer 56

In all species studied to date, there is an increase in **glucocorticoid** concentration in the fetal circulation towards term

Question 57

increasing fetal cortisol has what effect on the fetus

Answer 57

This increase in cortisol is responsible for maturing many tissues in preparation for extrauterine life, such as stimulating gluconeogenesis in the fetal liver. It also causes concomitant changes in the fetal concentrations of other hormones, e.g. tri-iodothyronine and adrenaline, which also contribute to maturation or functional activation of key tissues essential for neonatal survival.

Question 58

describe fetal cortisols effects on the gut

Answer 58

* acid secretions * digestive enxymes * mucosal turnover

Question 59

describe fetal cortisol effecs on adipose tissue

Answer 59

leptin production UCP expression

Question 60

describe fetal cortisol effects on the kidney

Answer 60

* GFR * tubular sodium reabsorbtion * deiodinase activity * GR and MR receptors * renin-angiotensin II system

Question 61

describe fetal cortisol effecs on hte lugn

Answer 61

surfactant production alveolar density and wall thickness elastin and collagen expression ebta-adrenergic receptors ACE enzyme activity

Question 62

effect of fetal cortiso on the liver?

Answer 62

glycogen and gluconeogenesis enzyme IGF gene expression beta adrenergic and GH angiotensin II receptros

Question 63

what hormonal changes lead to initiation of partiuition?

Answer 63

involve changes in cortisol, oestrogen and prostaglandin and oxytocin concentrations as seen in other species, ## Footnote **although there is little evidence for a prepartum decline in the maternal progesterone concentration in women**

Question 64

image for initation of partuition in women:

Answer 64

Question 65

believed process of partiution: (LONG)

Answer 65

1. activation of feta ladrenal gland = more fetal cortisol and dehydroepiandrosterone sulphate, DHEAS. 2. cortisol = maturity of key fetal tissues 3. increased DHEAS production results in a rapid rise in maternal oestrogen levels close to term 4. rise in oestrogen availability in the human uteroplacental tissues (amnion, chorion, decidua and myometrium) leads to **cervical ripening** and **increased uterine contractility via enhanced PG synthesis** 5.

Question 66

T or F ## Footnote Cervical softening and ripening is essential for delivery to occur.

Answer 66

T

Question 67

in women - can removing the progesterone block myometrial contraction?

Answer 67

no ## Footnote In women, there is no evidence of removal of the progesterone block to myometrial contraction, although there may be regional changes in the oestrogen to progesterone ratio and in expression of the different progesterone receptor isoforms, which may affect contractility in different regions of the uterus by local variations in PG synthesis and metabolism.

Question 68

what does CRH do?

Answer 68

corticotrophic releasing hormone: ## Footnote CRH is detectable in fetal and maternal plasma and rises in concentration towards term and in labour.

Question 69

what dfoes CRH act on?

Answer 69

CRH acts on (i) the fetal adrenal to increase DHEAS production directly and indirectly via the fetal pitiutary (ii) the uteroplacental tissues to increase PG availability and (iii) the myometrium to inhibit contractions via increasing cAMP

Question 70

In culture, trophoblast CRH production is inhibited by _________ and stimulated by _________ & \_\_\_\_

Answer 70

In culture, trophoblast CRH production is inhibited by **progesterone** and stimulated by **catecholamines** and **glucocorticoids**

Question 71

how does fetal growth cause myometrial activation

Answer 71

stretch of the human uterus with fetal growth appears to have an important role in increasing GAP junction proteins and, hence, in causing myometrial activation

Question 72

statement L ## Footnote Initiation and progression of human labour, therefore, involves a combination of fetal, local, mechanical and maternal factors

Answer 72

Initiation and progression of human labour, therefore, involves a combination of fetal, local, mechanical and maternal factors

Question 73

Answer 73

Question 74

describe the mechanism of myometrial contraction (7)

Answer 74

1. rising oestrogen increases contractile protein expression (actin and myosin) 2. Contraction of the filaments requires ATP generated by myosin light chain kinase 3. MLCK is activated by the calcium binding protein, calmodulin (CAM) which, in turn, is activated by Ca2+ ions. 4. During contractions, [Ca++]i increases by increase of Ca++ influx through Ca++ channels and by release of Ca++ stored in the sacroplasmic reticulum. 5. Uterotonins increase Ca2+i 6. agents that reduce myometrial activity act by inhibiting Ca++ release from the intracellular stores or by reducing MLCK activity. These inhibitory activities are often mediated via cAMP or cGMP 7. Contraction of the myocytes is coordinated by cell to cell coupling effected by formation of intercellular GAP junctions between adjacent myocytes. These GAP junctions depend on connexin proteins, expression of which is influenced by steroids and mechanical stretch on the uterus. Connexin abundance and the number of GAP junctions increase with the onset of labour.

Question 75

Agents that increase cAMP or cGMP, therefore, ______ uterine contractility (tocolytics).

Answer 75

Agents that increase cAMP or cGMP, therefore, decrease uterine contractility (tocolytics).

Question 76

These GAP junctions depend on connexin proteins, expression of which is influenced by ...... (myometrial muuscle developemnnt)

Answer 76

These GAP junctions depend on connexin proteins, expression of which is influenced by steroids and mechanical stretch on the uterus.

Question 77

image

Answer 77

Question 78

Labour is preceded by...

Answer 78

Labour is preceded by Braxton-Hicks contractions

Question 79

how many stages does labour have?

Answer 79

3

Question 80

describe the first stage of labour

Answer 80

**Stage 1: Increasing uterine activity and cervical dilation.** The ‘show’ of blood and mucus occurs at this stage. Cervix dilates to 10cm. Regular contractions force the babies’ head down into the birth canal, encouraging dilation and evoking neuroendocrine reflexes that produce the positive feedback element to labour. Lasts 10- 12h in primagravida (first pregnancy) and 6-8h in multigravida. Mild maternal hyperventilation.

Question 81

describe stage 2 of labour

Answer 81

**Stage 2: Expulsion of fetus.** This stage involves voluntary effort as well as uterine contractions. The baby also needs to engage, flex and rotate. Lasts 45-120min in primagravida and 15-45min in multigravida. Maternal breath holding. Most dangerous stage for the baby.

Question 82

describe stage 3 of labour

Answer 82

**Stage 3: Expulsion of placenta.** The uterus continues to contract until the placenta and membranes are delivered. Lasts 10min. Uterus cannot contract down effectively until the placenta is removed.

Question 83

Women with retained pieces of placenta are at risk of ...

Answer 83

Women with retained pieces of placenta are at risk of postpartum haemorrhage.

Question 84

3 factors which influence the time fo delivery?

Answer 84

 Light/dark cycle  Food supply  Infection

Question 85

Indications for C section include ....

Answer 85

Indications for C section include * cephalic-pelvic disproportion, * FGR and evidence of acute fetal distress, * previous C-section or uterine damage.

Question 86

Indications for induced delivery; (2) Methods of induction are either....

Answer 86

Indications for induced delivery; membranes ruptured \>72h, overdue \>10days. Methods of induction are either endocrine or mechanical.

Question 87

fat

Answer 87

mamba