Week 5 Flashcards
What are the 3 shunts found in foetal circulation?
What does this mean for oxygenation of blood?
Ductus venosus
Ductus arteriosus
Foramen ovale
These shunts mean that blood doesn’t travel to the lungs for oxygenation
At how many weeks gestation are the following lung developmental phases?
- pseudoglandular
- canalicular
- saccular
- alveolar
At what point does surfactant production begin?
Pseudoglandular - 3 weeks
Canalicular - 16 weeks
Saccular - 24 weeks
Alveolar - 36 weeks
Surfactant is produced from the saccular stage onwards (i.e. from 24 weeks)
What are some of the preparations made by the foetus in the 3rd trimester for delivery?
Production of surfactant
Accumulation of glycogen in the liver, muscles and heart
Accumulation of brown fat between the scapulae and around internal organs
Accumulation of subcutaneous fat
Swallowing of amniotic fluid
Describe what happens to a baby within the first few seconds of birth
Initially blue, then starts to breathe
Cries, which increases intrathoracic pressure and pushes fluid out of the air spaces in the lungs and into the interstitial tissues
Baby gradually goes pink as O2 sats go up to about 90% within the first 10 mins of life
Cord is then cut after 1-2 mins, too soon and the baby may become hypovolaemic/anaemic (more of a problem in pre-term babies)
What various changes occur in foetal circulation as it transitions to post-birth?
Pulmonary vascular resistance drops
Systemic vascular resistance rises
Oxygen tension rises
Circulating prostaglandins drop (due to removal of the placenta)
Ducts constrict and the foramen ovale closes
How is the ductus arteriosus closed at birth?
O2 is typically a potent vasodilator, however in the ducts it is a potent vasoconstrictor - as respiration begins this causes closure
Removal of the placenta (a v. low resistance organ) causes systemic resistance to rise, and blood to flow to the lungs where previously it hadn’t
The placenta also produces prostaglandins, specifically prostaglandin E2 to keep the DA open. Upon removal of the placenta, this removes the amounts of prostaglandins in the circulation and causes constriction of the ducts.
How can a patent ductus arteriosus be managed?
Conservative - watchful waiting to see if the duct closes itself
Medically - prostaglandin inhibitors may be given (either indomethacin or ibuprofen)
Surgically
What happens to the 3 shunts following changes in systemic circulation at birth?
Foramen ovale - closes, or remains patent in 10% of cases
Ductus arteriosus - becomes the ligamentum arteriosus, or may remain patent
Ductus venosus - becomes the ligamentum teres on the liver
What condition arises if normal circulatory transition fails?
What are the features of this condition?
Persistent pulmonary hypertension of the Newborn (PPHN)
Pulmonary hypertension, causing hypoxaemia (metabolic acidosis) secondary to a right-to-left shunting of blood at the foramen ovale and ductus arteriosus

How is PPHN managed?
Ventilation
Oxygen (babies tend to be resuscitated with normal air, not O2)
Nitric oxide (very potent vasodilator), works in a lot of babies, depending on the aetiology
Sedation
Inotropes - milrinone, vasodilator
Extra-corporeal life support (ECLS) - ECMO requires anticoagulants so has risks of clotting. This is a very specialised treatment
Why are newborn babies at risk of being too cold?
Large surface area in relation to their body weight + wet when born
Heat loss occurs by…
- babies being unable to shiver
- main source of heat production is non-shivering thermogenesis, which is inefficient in the first 12 hours of life
- peripheral vasoconstriction
Which babies are at greater risk of developing hypothermia?
How is this risk managed in post-natal care?
Small for dates/pre-term babies are at greater risk, but all babies need help to maintain their temperature
Smaller/pre-term babies have low stores of brown fat, little sub. cut. fat and a large surface area:volume
Hypothermia is managed with…
- drying the baby as soon as it is born
- dressing them in a hat and blanket/clothes
- skin-to-skin contact with mum as soon as possible
- heated mattresses
- incubators
How might a newborn baby develop hypoglycaemia?
Increased energy demands
- if unwell
- hypothermia
Low glycogen stores
- small
- premature
Inappopriate insulin:glucagon ratios
- maternal diabetes
- hyperinsulinism
Some drugs
- e.g. labetalol (used to treat high maternal blood pressure)
If left untreated, how might hypoglycaemia affect a newborn? How is this avoided/treated?
Inappropriately high insulin shuts off ketone production, which can result in brain damage in babies
Managed by…
- identifying high risk babies
- feeding effectively
- keeping babies warm
- monitoring carefully
How does a baby’s sucking affect the mother’s hypothalamus?
Creates a positive feedback loop
Post. pituitary releases oxytocin which causes milk ejection
Ant. pituitary releases prolactin which causes milk production
Describe the change in haemoglobin from neonate to adult. How might this lead to anaemia?
What chromosome is responsible for the different subunits of Hb?
Foetal haemoglobin is made up of alpha and gamma subunits
Adult haemoglobin is made up of alpha and beta subunits
At birth, synthesis of foetal haemoglobin ceases, however adult haemoglobin is made slower than foetal haemoglobin is broken down, which can result in physiological anaemia as well as physiological jaundice
Beta and gamma subunits are synthesised on chromosome 11
For how long should folic acid be taken at pregnancy?
400 micrograms daily for 3 months prior to conception, and also the first 3 months of pregnancy
What point of a pregnancy is there the greatest amount of teratogenic risk?
1st trimester, especially weeks 4-11
1st trimester is when organogenesis takes place, and if possible all drugs should be avoided unless maternal benefit outweighs the risk
Name some known teratogenic drugs. How do they affect the foetus?
ACE inhibitors/ARBs - cause renal hypoplasia
Androgens - can cause virilisation of female foetus
Antiepileptics - can cause cardiac, facial, limb and neural tube defects
Cyotoxics (e.g. chemo) - multiple defects, abortions
Lithium - cardiovascular defects
Methotrexate - skeletal defects
Retinoids (used for acne, similar to Vit. A) - ear, cardiovascular and skeletal defects
Warfarin - limb and facial defects
How might some drugs affect outcomes around term? Examples (think labour and baby after delivery)?
Adverse effects on labour
- adaptation of foetal circulation may be affected by NSAIDs resulting in premature closure of ducts
- suppression of foetal systems e.g. opiates causing respiratory depression
- bleeding e.g. caused by warfarin
Adverse effects on baby after delivery
- withdrawal symptoms e.g. caused by SSRIs and opiates
- sedation
What drug, when taken by mothers to prevent recurrent miscarriage (didn’t work), resulted in their children developing urogenital malignancies?
Diethylstilbestrol a.k.a. desplex
What antiepileptic drugs should be avoided in pregnancy?
Is it worth treating epileptic women while pregnant?
Avoid phenytoin and valproate
YES! Benefits of treating outweigh the risks in most cases, there is a 20-30% risk of congenital malformations if on 4 drugs, so monotherapy is preferred and be sure to give folic acid as well
Which antihypertensive agents are used in pregnancy?
Which ones should be avoided?
Older antihypertensives, as more is known about their effect in pregnancy
Labetalol
Methyldopa
(Nifedipine - not ideal, reserve for patients that don’t tolerate the above)
Avoid ACE inhibitors, ARBs and antidiuretics. Beta blockers may also inhibit foetal growth in late pregnancy
What medications should be used for the following acute problems?
- nausea and vomiting
- UTI
- Pain
- Heartburn
N+V - Cyclizine is safest
UTI - nitrofurantoin, cefalexin, or if 3rd trimester use trimethoprim
Pain - paracetamol
Heartburn - antacids
