Physiology of Pregnancy and Labour Flashcards by Katie Clark

List the cell stages a fertilised ovum goes through before implantation

Fertilised ovum
Cleavage (4-cell/8-cell stages)
Morula
Blastocyst

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During which days following fertilisation does the blastocyst enter the uterus?

Days 3-5

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During which days following fertilisation does the blastocyst attach to the lining of the uterus?

Days 5-8

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Which surface cells help the blastocyst penetrate and adhere to the endometrium?

Trophoblastic cells

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By what day following fertilisation does the blastocyst become fully buried in the endometrium?

Day 12

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Which tissue is the placenta derived from?

Trophoblast and decidual tissue

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How is the placental cavity formed?

Trophoblastic cells differentiate into syncitotrophoblasts which invade the decidua of the endometrium to form cavities filled with maternal blood

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How does the embryo communicate with the placenta?

Placental villi containing capillaries

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There is no direct contact between foetal and maternal blood. True/False?

True

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By which week of pregnancy are the foetal heart and placenta fully functional?

5th week

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HCG stimulates the corpus luteum to secrete what hormone?

Progesterone

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Oxygen-saturated blood goes to the foetus via which vessel?

Umbilical vein

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Oxygen-poor blood goes from the foetus to the mother via which vessels?

Uterine veins

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What 3 factors increase the supply of O2 to a foetus?

Foetal Hb has increases carrying capacity
Higher Hb concn in foetal blood
Foetal Hb can carry more O2 in low PCO2 (Bohr effect)

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Drugs can cross the placental barrier - list some teratogens

Thalidomide
Carbamazepine
Tetracyclines
Alcohol
Nicotine
Heroin, cocaine

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What is the effect of human chorionic somatomammotropin (HCS)?

Decreases insulin sensitivity of mother
Protein tissue formation
Breast development

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What effect does progesterone have on uterine contractility?

Decreases contractility

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What effect does oestrogen have on the uterus?

Increases size of uterus

Relaxation of ligaments

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What happens to the cardiac output during pregnancy?

Increases to cope with demands of uteroplacental circulation

Can be up to 50% above normal around 24wks!

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When does cardiac output typically decrease in pregnancy?

Last 8 weeks due to uterus compressing vena cava

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What happens to Hb levels during pregnancy? What is the consequence?

Decrease due to dilution of blood

Require iron supplements

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What effect does progesterone have on CO2 levels?

Stimulates brain to lower CO2 levels by increasing respiratory rate

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What is pre-eclampsia?

Pregnancy-induced hypertension and proteinuria

Taking folic acid during pregnancy reduces the risk of what?

Neural tube defects

Taking vitamin B during pregnancy helps what?

Make red blood cells (erythropoeisis)

Taking vitamin K before birthing prevents what?

Intracranial bleeding during labour

Towards the end of pregnancy, how does the ratio of oestrogen:progesterone change?

Ratio increases - oestrogen promotes contractility

Which hormone secreted from the posterior pituitary helps stimulate contractions in labour?

Oxytocin

Give an example of positive feedback from the foetus that increases contractility during labour

Cervical stretch due to foetus head | N.B. also increases oxytocin release

What are the 3 stages of labour?

1: cervical dilation (8-24hrs) 2: passage through birth canal (0-30mins) 3: expulsion of placenta

Oestrogen and progesterone inhibit milk production. True/False?

True | After birth, levels drop to facilitate lactation

Which hormone stimulates lactation?

Prolactin

What 2 stimuli cause lactation in the "milk let-down" reflex?

Baby crying | Baby suckling

What should be expelled from the uterus in normal labour?

Foetus Membranes Umbilical cord Placenta

What is Ferguson's reflex in labour?

Pressure on the cervix triggers a hormonal pathway that leads to uterine contractions and dilation of cervix

Why might hydrocortisone be given to a pre-term baby?

Help mature its lungs

There are 3 stages in labour. What does stage 1 comprise of?

Latent phase: 3-4 cm cervical dilation | Active phase: 4-10 cm cervical dilation

There are 3 stages in labour. What does stage 2 comprise of?

Full cervical dilation to delivery of baby

There are 3 stages in labour. What does stage 3 comprise of?

Delivery of baby to expulsion of placenta and membranes

Describe the clinical features of the latent phase of stage 1 of labour

Mild irregular intrauterine contractions Cervix softens and shortens May last a few days

Describe the clinical features of the active phase of stage 1 of labour

Contractions become more rhythmic and intense Cervix achieves full dilation Slow descent of presenting part of baby

When is stage 2 of labour considered prolonged in a nulliparous woman?

If it exceeds 3 hours where there is analgesia | If it exceeds 2 hours where there is no analgesia

When is stage 2 of labour considered prolonged in a multiparous woman?

If it exceeds 2 hours where there is analgesia | If it exceeds 1 hour where there is no analgesia

Why are oxytocic drugs recommended for stage 3 of labour?

Help contractions | Reduce risk of post-partum haemorrhage

What chemical causes cervical softening?

Hyaluronic acid

What causes cervical ripening during labour?

Decrease in collagen fibre alignment and tensile strength

What are Braxton Hicks contractions?

Tightening of the uterine muscles to aid body to prepare for birth Not usually felt until 2nd/3rd trimester

How long typically are the gaps between "true labour contractions"?

5 minutes

How do Braxton Hicks contractions differ from true labour contractions?

BHC: irregular, do not increase in frequency/intensity, resolve with change in activity TLC: regular, increasing frequency/intensity, don't resolve

What does it mean if a baby is "born in a caul"?

Born with some membrane/amniotic sac still surrounding it

Describe the "normal" presentation of a baby as it passes through the pelvic canal

Longitudinal lie, cephalic presentation | Occipito-anterior, then occipito-transverse with flexed head

What presentations are classified as "abnormal" in a baby's birth?

Transverse/oblique/breech lie | Occipito-posterior engagement

There is a relationship between the clinical state of the cervix and the onset of labour. Which 5 parameters are assessed under the Bishops score?

``` Effacement Dilation Firmness Position Level of presenting part ```

List options for analgesia during labour

``` Paracetamol TENS Entonox Diamorphine Epidural anaesthesia Remifentanyl ```

What would be considered an abnormal amount of blood loss during labour?

More than 500ml

When does placental expulsion occur following delivery?

5-10 mins | Considered normal up to 30 mins

How long does it take tissues to return to non-pregnant state in puerperium?

6 weeks