Thrombocytopenia in Pregnancy

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Here’s the RoshReview Question of the Week!

A 23-year-old primigravid woman at 25 weeks gestation presents to the prenatal appointment to follow up on lab results. Her platelet count is noted to be 77,000/μL, decreased from 205,000/μL in the first trimester. She reports no abnormal bruising or bleeding. What is the most likely reason for her thrombocytopenia?

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Practice Bulletin 207 is our companion reading this week!

Introduction 

  • Evaluation of thrombocytopenia in pregnancy can be difficult because there are many things that could cause it - not all of them are related to pregnancy 

  • Definition: when platelets are <150,000/microL 

  • So what is normal? 

    • Recall in our very first few episodes that pregnancy can lead to increased plasma volume and not necessarily an equal increase in blood components 

    • This can lead to what appears to be some dilutional effects 

    • In the National Health and Nutrition Examination Survey (NHANES), the mean plt count in pregnancy is as follows: 

      • Non pregnant: 273k 

      • 1st trimester: 251k

      • Second trimester 230k

      • Third trimester 225k 

      • Delivery 217 k 

      • Postpartum (7 weeks) 264k  

  • Definitely suggests that some decrease in platelet count could be expected in pregnancy

What are the causes of thrombocytopenia in pregnancy?

  • Gestational thrombocytopenia - benign and self limited; may even occur in the first trimester, but usually is more common as pregnancy continues; frequency is 5-10% at the time of delivery

    • But remember this is a diagnosis of exclusion! It’s acceptable if there is mild thromboctyopenia, but again, you should look if Plt <100k  

  •  Immune Thrombocytopenia (ITP) - 1-3/10,000 pregnancies, but really low plts only affect a small portion of these

    • ITP is more frequent in pregnancy than in the general adult population but may be because of recognition (checking more frequent CBCs in preg) 

    • Autoimmune condition where antiplatelet antibodies interfere with platelet production and causes destruction of circulating platelets

      • Diagnosis based on exclusion of other causes of thrombocytopenia  

  • Preeclampsia/HELLP Syndrome

    • Remember that it is very rare <24 weeks, and there are usually other signs and symptoms as well like elevated BP, headache, vision changes, etc. As well as other hematologic abnormalities like anemia due to hemolysis (high LDH), and may have abnormal LFTs 

    • We won’t go too much into preeclampsia since we discuss it elsewhere, but always something to keep in mind 

  • Less likely things, but still things to keep in mind 

    • DIC - Disseminated intravascular coagulation

      • There is usually an underlying cause of this such as placental abruption, sepsis, etc 

      • Patients will have bleeding and oozing at IV sites for example 

      • Usually will have low fibrinogen and elevated PT and PTT labs as well  

    • Acute fatty liver of pregnancy 

    • Thrombotic thrombocytopenic purpura (either immune or hereditary)

      • Will usually present with purpura, can have neurological changes, fever, kidney injury, can have elevated BPs and may be confused with PEC 

      • Will have reduced activity of ADMATS13, but this may be a send out lab in most places and will not come back for some time 

      • Will have schistocytes on smear 

    • Lupus 

    • Infection

    • Inherited platelet disorders

So… when should we start to worry?

  • When platelets are: 

    • If platelets are between 100k-150k if there are risk factors present (but usually, do not need work up and can be attributed to gestational thrombocytopenia) 

    • At any point <100k (usually this is beyond the lower end of gestational thrombocytopenia)

      • Plts of <100k only occur in 1% of uncomplicated pregnancies 

      • Remember that there is increased risk of spontaneous bleeding if Plt <20k 

      • Some institutions have cut offs for platelets for ability to give neuraxial analgesia - some places are 70-80k, some places are 100k. Please check with your institution and your patients, because this may require treatment or your patient won’t get an epidural! 

Ok, so that’s a lot of causes… how do I go about figuring out what to do? 

  • Evaluation of the patient

    • Get a good history and physical - this can sometimes help you determine what it is not

      • If patient is well appearing, with no pain, vaginal bleeding, elevated blood pressure or other complaints, it’s usually not going to be something like AFLP, DIC, TTP, or preeclampsia  

      • Look through the patient’s chart: what were their platelets before? What other medical problems? What about new medications? 

      • Any history of lupus, TTP, liver disease, anemia

      • You have the CBC - did the lab do a smear? Are there abnormalities on the smear, like schistocytes? 

      • Most of the time, if you have someone who is sitting in the clinic and appears well, you may have some time  

  • The asymptomatic patient with Plt >100k

    • Usually, plts between 100-150k without other cytopenis or other major clinical findings can be attributed to gestational thrombocytopenia 

    • The other major cause could be ITP, but minor ITP with plt >100k also does not need treatment 

    • Our practice is to check plts monthly to make sure they do not drop below 100k, or below threshold for neuraxial analgesia 

  • The asymptomatic patient with Plt <100k 

    • Review the CBC - make sure there are no other cytopenias; ask for a smear 

    • Evaluate for HIV (usually already done in pregnant patients), as this could also lead to thrombocytopenias 

    • Obtain other coagulation panel like PT, PTT, fibrinogen level 

    • Also obtain CMP - evaluate kidney and liver function 

    • If no obvious signs, it is ok to get hematology involved early

    • More likely to be ITP if <100k, and patients can be treated with steroids or even IVIG in refractory cases if needed 

    • This is to make sure that the platelets do not drop further so that they cannot get neuraxial analgesia or so that they don’t drop too low as to cause issues with bleeding 

  • What if they are symptomatic and <100k?

    • A lot of this is going to depend on their history and physical again - we are usually pretty good at evaluating for preeclampsia - get their vital signs and do your exam

      • Do they have fever? Purpura? 

    • Labs: CBC, CMP, coag panel, HIV, LDH, urinalysis, bilirubin 

    • If you are suspicious of TTP (ie. fevers, kidney injury, neurological changes) 

      • Make sure to get CT head to rule out bleed 

      • ADAMTS13 

      • Hematology consult 

    • Ok to get MFM and hematology involved early 

Management 

  • Treatment for bleeding or severe thrombocytopenia 

    • If Plt are <10k or <20k, there is increased risk of spontaneous bleed 

    • If Plt <20k and severe bleed (ie. intracranial), you should give platelets regardless of the underlying cause of thrombocytopenia (yes, even in ITP if it will get consume)

  • Some platelet thresholds to consider in delivery 

    • Vaginal delivery: 20-30k 

    • C/S: 50k 

    • Neuraxial anesthesia: institution based; ours is 80k; most institutions will have a count between 50-80k 

  • Other considerations 

    • Operative vaginal deliveries are relatively contraindicated if there is severe maternal thrombocytopenia 

    • This is because there is concern that there could also be fetal thrombocytopenia (ie. immune mediated or hereditary) 

    • However, if you must perform an operative delivery, forceps is favored over vacuum 

    • Remember: Just because someone has ITP does not mean they can’t have an operative delivery 

  • Treatment of specific disorders 

    • ITP - steroids or IVIG 

      • Dosing of steroids: prednisone 1mg/kg/day for two weeks followed by gradual taper; may need 2 weeks to see peak effect (usually 1-4 weeks for peak) 

      • IVIG should be given at least 1 week in advance to allow for maximal efficacy and platelet count retesting if trying to raise platelet counts for epidural 

      • If refractory, other methods in pregnancy are not well studied, and you should have a conversation with your MFM and hematology colleagues 

    • TTP - plasma exchange

    • Preeclampsia or DIC due to abruption: delivery! 

  • What about fetal testing of platelets?

    • There isn’t really evidence to suggest we should test fetal platelets (ie. either via PUBS or from fetal scalp during labor

    •  We won’t discuss fetal/neonatal thrombocytopenia here, but just some brief reasons to test neonatal platelets: 

      • Maternal ITP 

      • Neonatal thrombocytopenia in previous pregnancy (concern for NAIT, though this is usually not associated with maternal platelet issues) 

      • Congenital anomalies associated with thrombocytopenia 

      • Bleeding or petechia on the infant 

      • Neonatal infections (ie. CMV, rubella)