Haem: Obstetric Haematology Flashcards
What haematological changes are seen on FBC in pregnancy?
- Mild anaemia (DILUTION)
- Red cell mass rises (120-130%)
- Plasma volume rises (150%)
- Macrocytosis
- Normal
- Folate or B12 deficiency
- Neutrophilia
- Thrombocytopenia
- Increased platelet size
What are the 3 Hb thresholds for anaemia in pregnancy?
<110 in 1st trimester
<105 in 2nd/ 3rd trimester
<100 post partum
What are the increased demands required in pregnancy?
- Iron requirement
- 300mg for fetus
- 500mg for maternal increased red cell mass
- Folate requirements increase
- Growth and cell division
- Approx additional 200mcg/day required
How iron deficiency diagnosed?
What is the treatment for iron deficiency in pregnancy?
FBC: Low Hb, MCV < 80
200 mg ferrous sulfate daily for 3 months
What does iron deficiency during pregnancy increase risk of?
IUGR
Prematurity
Postpartum haemorrhage
What is normal iron absorption per day?
What is iron absorption during pregnancy?
Normal absorption 1-2mg a day.
This increases to 6mg during pregnancy.
Why is iron absorption increased during pregnancy?
Hepcidin decreases and ferroportin levels increase. This results in increased iron absorption.
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What are the RCOG recommendation for daily folate intake?
400 mcg daily
What does folate deficiency increase risk of during pregnancy?
Neural tube defects
What is the cut off level of platelets required for:
- Epidural anaethesia
- Delivery
- > 70 x10^9/L
- > 50 x10^9/L
Higher for epidural due to serious risk of spinal haematoma
What are causes of thrombocytopenia in pregnancy?
- Physiological:
- ‘gestational’ / incidental thrombocytopenia
- Pre-eclampsia
- Immune thrombocytopenia (ITP)
- Microangiopathic syndromes
- All other causes: bone marrow failure, leukaemia, hypersplenism, DIC etc.
What is the most commone cause of thrombocytopaenia <150x109/L in pregnancy?
Gestational thrombocytopenia
What is the most common cause of thrombocytopaenia <100x109/L in pregnancy?
ITP and pre-eclampsia
This suggests something pathological is occurring.
What is gestational thrombocytopenia?
A physiological decrease in platelet count of about 10% during pregnancy
Does not affect foetus.
What is the underlying mechanism of gestational thrombocytopenia?
Mechanism poorly defined.
Possibly due to dilution and increased consumption.
When does platelet count increase following gestational thrombocytopenia?
Platelet count rises around 2-5 days after delivery
When does platelet count fall most during pregnancy in gestational thrombocytopenia?
Most of the fallen platelet count occurs in 3rd trimester
What percent of women with preeclampsia get thrombocytopenia?
50%
Thrombocytopenia is proportionate to severity of preeclampsia.
What causes thrombocytopenia in preeclampsia?
Increased activation and consumption of platelets due endothelial injury
What percentage of thrombocytopenia during pregnancy is accounted for by immune thrombocytopenia (ITP)?
5% of thrombocytopenia in pregnancy
- TP may precede pregnancy
- Early onset
What are the treatment options for ITP in pregnancy?
- IVIG (FIRST LINE)
- Steroids (not ideal as lots of side effects)
At what point during the pregnancy does platelet count fall most due to ITP?
Platelet count tends to fall dramatically early in pregnancy if present
Does ITP affect the baby?
Yes / Potentially
Anti-platelet IgG can cross the placenta (5-10%). If foetal platelet count drops can increased risk of intracranial haemorrhage. Check platelet count at birth and give IVIG if below 50.
What is mechanism of microangiopathic haemolytic anaemia?
Deposition of platelets and fibrin in microvasculature leading to thrombocytopenia. The deposits can also shear RBCs leading to intravascular haemolysis. Organ damage can also occur due to vessel occlusion
What would you expect to see on the blood film of microangiopathic syndromes?
Schistocytes
Nucleated red cells consistent with increased red cell turnover
What are the causes of MAHA in pregnancy?
- Preeclampsia
- HELLP
- TTP (Thrombotic thrombocytopenic purpura)
- HUS (Haemolytic uraemic syndrome)
- AFLP (Acute fatty liver of pregnancy)
- SLE (Systemic lupus erythema)
- APLS (Antiphospholipid syndrome)
What is HELLP?
Haemolysis
Elevated liver enzymes
Low platelets
What is a leading cause of maternal mortality?
Coagulation changes in pregnancy - VTE
What change in pro- and anti-coagulative factors are seen in pregnancy?
Hypercoagulability
- Factor VIII and vWF - increases x3-5
- Fibrinogen - increases x2
- Factor VII -increases x0.5
Hypofibrinolytic
- Protein S - falls to half basal level
- PAI-1 - increases x5 fold
- PAI-2 produced by the placenta
What is the reason for coagulation changes seen in pregnancy?
Rapid control of bleeding from the placental site (700ml/min) at time of delivery. Coagulation changes control this bleeding.
What are the net effects of coagulation changes seen in pregnancy?
- Increased thrombin generation
- Increased fibrin generation
- Reduced fibrinolysis
- Interact with other maternal factors
This leads to an increased rate of THROMBOSIS
When do coagulation changes in pregnancy return back to normal?
Weeks/months after delivery
When are VTEs most likely to occur?
1-6 weeks post partum
When are deaths due to pulmonary embolism during pregnancy most likely to occur?
A third of cases are post-partum (within 6 weeks post-partum). However, a reasonable proportion also occur in the first trimester.
What investigations for VTE may be done during pregnancy?
Doppler and VQ scans are SAFE to perform in pregnancy CTPA in some cases although increases maternal breast cancer risk
(D-dimer is often elevated in pregnancy so is NOT useful for exclusion of thrombosis)
What are three main factors that increase risk of VTE?
Virchow’s Triad
- Changes in blood coagulation (hypercoaguability)
- Reduced venous return (stasis)
- Vessel wall changes
What are variable factors during pregnancy that increase risk of thrombosis?
- Hyperemesis/dehydration
- Bed rest/immobility
- Obesity
- Preeclampsia
- Operative delivery (C-sections)
- Previous thrombosis/thrombophilia
- Age >35 significant
- Parity - after 4th child, risk increases massively
- Multiple pregnancy
- Other medical problems: HbSS, nephrotic syndrome
- IVF: ovarian hyperstimulation
How may thrombosis be prevented in pregnant women?
Identify women with risk factors at booking
- Thromboprophylaxis - LMWH
- Mobilise early
- Maintain hydration
Describe antenatal and postnatal thromboprophylaxis management in:
1. High risk women
2. Intermediate risk women
3. Low risk women
- High risk: antenatal LMWH continued until 6 weeks postpartum
- Intermediate risk: consider antenatal LMWH either starting in first trimester (4 risk factors) or from 28 weeks (3 risk factors) until 10 days postpartum
- Low risk: mobilisation and avoidance of dehydration throughout
What is the treatment of thromboembolic disease in pregnancy?
LMWH
- Safe as does not cross placenta
- RCOG recommend once or twice daily injections
- After 1st trimester monitor anti-Xa
- Stop LMWH for labour or planned delivery, esp. for epidural
Epidural: wait 24 hours after treatment dose, 12 hours after prophylactic dose
What anticoagulant drugs must you avoid in pregnancy?
Warfarin and DOACs
- Both cross the placenta and are teratogenic
- Especially in 1st trimester
What complications of pregnancy are associated with thrombophilia?
It is hypothesised that an increased tendency to thrombosis is associated with impaired placental circulation.
This results in:
- Fetal growth restriction (IUGR)
- Recurrent miscarriage
- Late fetal loss
- Placental abruption
- Severe preeclampsia
What is the diagnostic criteria of antiphospholipid syndrome?
At least 1 clinical and 1 biochemical criteria
Clinical criteria:
- Vascular thrombosis
- Pregnancy morbidity
Biochemical criteria
(all must be on 2 occasions >12 weeks apart)
- Lupus anticoagulant
- High anticardiolipin antibodies
- Anti-b2-glycoprotein 1 antibodies
What are the diagnositic criteria of pregnancy morbidity in anti-phospholipid syndrome?
- Adverse pregnancy outcome: three or more consecutive miscarriages before 10 weeks of gestation (where anatomical, hormonal, and chromosomal causes have been excluded)
- One or more morphologically normal fetal losses after the 10th week of gestation
- One or more preeterm births before the 34th week of gestation owing to placental disease
What treatment may be given to improve outcome in women who have had recurrent miscarriages?
Aspirin
OR
Aspirin + Heparin
What is placenta praevia?
When the placenta covers the cervical os
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What is placenta accreta?
When the placenta is attached to the surface of the myometrium
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What are placenta increta and percreta?
Placenta increta: the placenta penetrates into the myometrium
Placenta percreta: the placenta penetrates through the myometrium to the uterine serosa
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What do C-sections increase the risk of in future pregnancies?
- Placenta praevia
- Placenta accreta
C-sections increase the likelihood of having issues with the site of placental implantation
What is the definition of post-partum haemorrhage?
> 500 ml blood loss
What are the main causes of postpartum haemorrhage?
4 T’s:
Tone: uterine atony (main cause)
Trauma: perineal tears
Tissue: placenta accreta
Thrombin: hypocoagulative state (DIC in aminotic fluid embolism)
Name some obstetric causes of DIC
- Amniotic fluid embolism
- Placental abruption
- Retained products of conception
- Severe preeclampsia
- Sepsis
What is amniotic fluid embolism?
AFE is a rare childbirth (obstetric) emergency in which amniotic fluid enters the bloodstream of the mother to trigger a serious reaction.
Very catastrophic with high mortality rate (86%)
What are the symptoms of AFE?
- ARDS - SoB, hypoxia
- Shock
- Neurological - confusion, coma, seizures
- DIC
Manifests during labour or immediately after but can occur up to 48 hours postpartum
Which haemoglobinopathies are screened for?
- Sickle cell disease
- Alpha thalasaemia
- Beta thalasaemia
How are individuals selected for the haemoglobinopathy screening program
- If from high prevalance area
- Family Origin Questionnaire
What diagnostic technique is used in the haemoglobinopathy screening program?
What can this techique not diagnose?
High performance liquid chromatography
HPLC can identify haemoglobin variants (EXCEPT it cannot identify alpha thalassaemia)
- Alpha thalassaemia requires DNA diagnosis.
- HPLC can quantify HbA2 (>3.5% = beta thalassemia)
What antenatal tests may be done to diagnose potential foetal haemoglobinopathies?
- CVS (10-12 weeks)
- Amniocentesis (15-17 weeks)
- Fetal blood sampling
- Ultrasound screening for hydrops
What are the key features of haemoglobinopathy counselling?
Important disorders are all recessive
Therefore if mother is heterozygous partner should be tested
Combinations as important as homozygous states
Prenatal diagnosis by 12 weeks: allows for termination of pregnancy in severe cases
What are the differences in FBC and Hb electrophoresis of iron deficiency anaemia vs. thalassaemia trait?
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Name 2 other important immune disorders in pregnancy that affect the neonate.
- Haemolytic disease of the newborn (HDN)
- Neonatal alloimmune thrombocytopenia (NAITP)
Maternal immune responses against fetal antigens requiring monitoring and intervention during pregnancy.