Obstetric Haematology Flashcards
What are the changes to FBC in pregnancy?
- Mild anaemia
- Red cell mass rises (120-130%)
- Plasma volume rises (150%) - net dilution
- Macrocytosis
- Normal
- Folate or B12 deficiency
- Neutrophilia
- Thrombocytopenia
- Increased platelet size
Describe the demands on different aspects of blood during pregnancy
- Iron requirement
- 300mg for fetus
- 500mg for maternal increased red cell mass
- RDA 30 mg - Increase in daily iron absorption 1-2mg to 6mg
- Folate requirements
- Growth and cell division
- Approx additional 200mcg/day required
What can iron deficiency cause for the fetus and mother?
- Intrauterine growth restriction
- Prematurity
- Postpartum haemorrhage
Describe the normal Iron cycle, and how iron is used in the body.
- Out of the 10-20mg iron in the diet
- 6mg is absorbed/day
- Transferrin transports iron in the blood
- 1-2mg iron/day is lost through desquamation of epithelia
- Hepicidin (75%)–> and goes into to haemoglobin and the process of erythropoiesis
- 10-20% goes to make up ferritin
- 5-15% goes to form part of other processes
- What is the pregnancy iron requirement?
- What is the recommended daily amount of iron?
1.
- 300mg: fetus
- 500mg: maternal red cell mass expansion
- 30mg/day
What does WHO recommend for pregnant women regarding iron and folate supplements in pregnancy?
- WHO recommends 60mg Fe and 400mcg folic acid daily during pregnancy
- Cochrane review - maternal Hb higher, Fe reserves higher, fetal ferritin higher but Fe/folate supplements were shown to have no effect on maternal or fetal outcome
What are RCOG recommendations for folate and iron supplements in pregnancy?
- Folic acid
- Advice reduced risk of neural tube defects
- Supplement before conception and for > 12 weeks gestation
- Dose 400ug/day
- Iron
- No routine supplementation in UK
What happens to platelet counts in pregnancy?
- Platelet count falls in pregnancy
- Non pregnant - 225-249x109/l
- Pregnant - 175-199x109/l
- 13% of women have platelets less than 150x109/l
What are the causes of thrombocytopenia in pregnancy?
- Physiological
- Gestational/incidental thrombocytopenia - most common
- Pre-eclampsia
- Immune thrombocytopenia - most common in severe thrombocytopenia (<70x109)
- Microangiopathic syndromes
- All other causes
- Bone marrow failure
- Leukemia
- Hypersplenism
- DIC
Describe gestational thrombocytopenia
- Physiological decrease in platelet count approx 10%
- >50x109/l sufficient for delivery (>70 for epidural)
- Mechanism poorly defined
- Dilution and increased consumption
- Baby not affected
- Platelet count rises Day 2-5 post delivery
Describe the relationship between preeclampsia and thrombocytopenia
- 50% of people with preeclampsia get thrombocytopenia (proportionate to severity)
- Probably due to increased activation and consumption
- Associated with coagulation activation
- Usually remits following delivery
Describe the following about immune thrombocytopenia:
- In pregnancy
- Treatment options
- Effect on baby
1.
- 5% of thrombocytopenia in pregnancy
- Thrombocytopenia may precede pregnancy
- Early onset
2.
- Treatment options:
- IV immunoglobulin
- Steroids etc
- Anti-D where Rh D positive
- Effect on baby
- Unpredictable (platelets <20 in 5%)
- Check core blood and then daily
- May fall for 5 days after delivery
- Bleeding in 25% of severely affected
- Usually normal delivery
Describe mircoangiopathic syndromes such a MAHA
- Deposition of platelets in small blood vessels
- Thrombocytopenia
- Fragmentation and destruction of red blood cells
- Organ damage (kidney, CNS, Placenta)
What does the image show?
Microngiopathic haemolytic anaemia (MAHA)
Film:
- Fragments
- Low platelets
- Polychromasia
What are the major coagulation changes in pregnancy?
- Hypercoagulable
- Factor VIII and vWF - Increase 3-5 fold
- Fibrinogen - increases 2 fold
- Factor VII increases 0.5 fold
- Hypofibronlytic
- Protein S - falls to half basal
- PAI-1 and PA1-2 - increase 5 fold
This allows for rapid control of bleeding from placental site (700ml/min) at time of delivery
What is the net effect of the coagulation changes in pregnancy?
A procoagulant state
- Increased thrombin generation
- Increased fibrin cleavage
- Reduced fibrinolysis
- Interact with other maternal factors
Increased rate of thrombosis
When is the risk of developing a PE highest in pregnancy?
Highest risk in the 40-46 weeks gestation, followed by first trimester
What are the main risk factors for VTE identified in women who died of a PE?
- BMI >25
- Family/personal history of VTE
What is the incidence of thrombosis in pregnancy?
- 1 per 1000 <35 years
- 2 per 1000 >35 years
- Relative risk approx x10
- One third are post-partum
What tests can be used in pregnancy safely to diagnose VTE?
- Doppler
- VQ scan
- D-dimer - but this is often raised in pregnancy and will not exclude thrombosis
What are the factors increasing risk of thrombosis in pregnancy?
- All
- Variable
- All
- Changes in blood coagulation
- Reduced venous return (85% left DVT)
- Vessel wall
- Variable
- Hyperemesis/dehydration
- Bed rest
- Obesity (BMI>29 3x risk of PE)
- Pre-eclampsia
- Operative delivery
- Previous thrombosis/thrombophilia
- Age
- Parity
- Multiple pregnancies
- Other medical problems - HbSS, nephrotic syndrome
- IVF - ovarian hyperstimulation
How can thromboembolic disease be prevented in pregnancy?
- Women with risk factors should recieve prophylactic heparin and TED stockings
- Either throughout pregnancy or in peri-post-partum period
- Highest risk gets adjusted dose LMWH
- Mobilize early
- Maintain hydration
What is the treatment for thromboembolic disease in pregnancy?
- Management:
- LMWH as for non-pregnant
- Does nor cross placenta
- RCOG recommend once or twice daily
- Do not convert to warfarin as it can cross the placenta
- After 1st trimester monitor anti Xa
- Stop for labour or planned delivery esp. for epidural
What is the issue with warfarin and pregnancy?
Warfarin can cross the placenta. Warfarin is teratogenic in weeks 6-12 and can delay developments
What are the complications of pregnancy hypothesized to be due to thrombophilia?
The hypothesis is that an increased tendency to thrombosis is associated with impaired placentl circulation
- Resulting in
- IUGR
- Recurrent miscarriage
- Late fetal loss
- Abruptio placentae
- Severe PET
What pregnancy complications occur in women with Antiphospholipid syndrome?
- Recurrent miscarriage and persistent lupus anticoagulant/anticardiolipin antibodies
- Adverse pregnancy outcome - 3 more more miscarriages consecutively before 10 weeks gestation
- One or more morphologically normal fetal losses after 10th week of gestation
- One or more preterm birthd before the 34th week of gestation owing to placental disease
What can be fatal causes of bleeding in pregnancy (post-partum)?
- Placenta praevia
- Placenta accreta - principal reason for having hysterectomy
Use of major obstetric haemorrhage protocols
Describe non-fatal bleeding in pregnancy
- Post partum haemorrhage - >500ml blood loss
- 5% of pregnancies have blood loss >1 litre at delivery
- Requires transfusion post partum
What are the mechanisms of post-partum haemorrhage?
- Major factors are:
- uterine atony
- trauma
- Haematological factors are minor except:
- dilutional coagulopathy after resuscitation
- DIC in abruption, aminiotic fluid embolism etc
Describe pregnancy and disseminated intravascular coagulation (DIC)
- Coagulation changes in pregnancy predispose to DIC
- Decompensation precipitated by:
- Amniotic fluid embolism
- Abruptio placentae
- Retained dead fetus
- Severe preeclampsia
- Sepsis
Describe an amniotic fluid embolism
- Epidemiology
- Signs
- Pathophysiology
- “The most catastrophic event in modern obstetrics”
- 1 in 20,000-30,000 births
- Sudden onset shivers, vomiting, shock, DIC
- 86% mortality
- Presumed due to tissue factor in amniotic fluid entering maternal bloodtream
- Almost all >25 years
- Usually 3rd trimester
- Drugs to induce labor e.g. misoprostol increase risk
- Why is haemoglobinopathy screening done?
- What screening is available?
1.To avoid birth of children with:
- alpha 0 thalassaemia (Hb Barts, gamma 4)
- Beta 0 thalassaemia - transfusion dependent
- HbSS - sickle cell disease (reduced life expectancy)
- Other compound HbS syndromes - symptomatic and risk of stroke
- NHS sickle cell and thalamassemia screening programme 2009
- Important to know compounds as well as homozygous states for parents
- All disorders are recessive
What are the options if haemoglobinopathy screening is needed?
- Proceed
- Prenatal diagnosis at:
- CVS sampling (10-12 weeks)
- Aminocentesis (15-17 weeks), fetal blood sampling
- Ultrasound screening for hydrops
Describe sickle cell disease in pregnancy
- Epidemiology/path
- Complications
- Management
1.
- HbSS - sickle cell anaemia
- HbS - clinically normal
- Vaso-occlusive crises become more frequent
- Anaemia and existing chronic diseases exaggerated
- Complications
- Fetal growth restriction
- Miscarriage, preterm labour, ?pre-eclampsia
- Venous thrombosis
- Management
- Red cell transfusion (top up or exchange)
- Prophylactic infusion
- reduced number of vaso-occlusiv episodes
- Not clear whether affects fetal or maternal outcome
- Alloimmunisation - extended phenotype
Compare and contrast what happens to the following in Iron deficiency anaemia vs thalassaemia trait
- Hb
- MCH
- MCHC
- RDW
- RBC
- Hb electrophoresis
What is haemolytic disease of the newborn?
Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis fetalis, is an alloimmune condition that develops in a peripartum fetus, when the IgG molecules (one of the five main types of antibodies) produced by the mother pass through the placenta.
What is neonatal alloimmune thrombocytopenia?
Maternal immune responses against fetal angitens causes a reduction in platelets, and is one of the leading causes of severe thrombocytopenia seen in newborns
