HTN in pregnancy Flashcards
How common in HTN in pregnancy ?
10-15% of pregnancies are affected (very common)
What percentage of primigravid (1st pregnancy) women are affected by pre-eclampsia (PET)?
- 10% are affected by mild PET
- 1% are affected by severe PET
What is the commonest cause of elective (medically induced) prematurity i.e. needing to have the baby born before premature due to risks to mother or baby?
PET
Describe the changes to BP during pregnancy and why they occur
- BP initially falls during early pregnancy reaching its lowest point at 22-24 weeks. After this is steadily rises
- This is because pregnancy causes vasodilation which results in a decreased SVR, there is an increase in CO but it is outmatched.
Note BP = SVR x CO
Following delivery of the baby what happens to the mothers BP ?
- It falls initially but then rises and peaks at days 3/4 postnatally
- By 6 weeks postnatally BP should be back to normal (easy to remember because puerperium i.e. when things are returning to normal only lasts 6 weeks)
How is HTN diagnosed in pregnancy ?
- By a BP of ≥ 140/90 on 2 occasions, followed by ambulatory BP monitoring or home BP monitoring if they cant use ABPM to confirm diagnosis
- OR by BP > 160/110 once, if severe BP (i.e. > 160/110) then consider starting on anti-HTN immediately without waiting for ABPM or HBPM
State the classifications for the severity of HTN
- Mild HTN = 140/90 → 149/99
- Moderate HTN = 150/100 → 159/109
- Severe HTN = ≥ 160/110
What are the 3 HTN disorders in pregnancy ?
- Pre-exisiting (chronic/essential) HTN
- Pregnancy induced HTN (gestational)
- Pre-eclampsia (PET)
Define what pre-existing (chronic/essential) HTN is in pregnancy
It is HTN present at booking or < 20 weeks (basically they had it prior to pregnancy because BP should be decreasing during this part of pregnancy)
Define what pregnancy induced HTN is
New HTN presenting > 20 weeks into pregnancy without any significant proteinuria
What secondary causes should you consider for pre-exisiting (chronic/essential) HTN in pregnancy ?
Renal, cardiac, cushings, conn’s, phaechromocytoma
When is pre-exisiting HTN in pregnancy often diagnosed ?
- It is often actually diagnosed prior to pregnancy
Note if it doesn’t resolve within 3 months post-delivery then can be retrospectively diagnosed as pre-exisiting HTN
What are the risks of HTN in pregnancy ?
- PET
- IUGR
- Placental abruption
What are the characteristic features of pregnancy induced HTN ?
Occurs during the second half of pregnancy and it resolves within 6/52 post delivery
The rate of recurrence of pregnancy induced HTN is high in subsequent pregnnacies - T or F?
True
Define what PET is
It is a pregnancy specific multi-system disorder with unpredictable, variable & widespread maniifestations
What are the characteristic features of PET ?
- New HTN after 20 weeks + Significant proteinuria
- +/- oedema as it is non-specific
Describe the pathogenesis of PET
- The primary defect is failure of trophoblastic invasion of spinal arteries
Spinal arteries proide blood to the interoplacental junction (from mother), normally you get cytotrophoblastic invasion which destroys some of the tunica smooth muscle allowing spiral arteries to open up and become high capacity, low resistance vessels
But in PET you get lack of cytotrophoblastic invasion ==> spiral arteries fail to adapt into high capacity low resistance vessels ==> they are narrower causing higher pressure & decreased flow to placenta ==> widespread endothelial damage & dysfunction ==> endothelial activation occurs causing increased capillary permeability, expression of CAM, prothrombotic factors, platelet aggregation and vasoconstriction
What are the symptoms of PET ?
- Headache
- Visual disturbance
- Epigastric / RUQ pain
- Nausea / vomiting
- Rapidly progressive oedema