• Nathan Riley, MD

Obgyno Wino Podcast Episode 14 - Thrombocytopenia in Pregnancy

"Education Must Not Simply Teach Work — It Must Teach Life" —W.E.B. DuBois

2016 Reserva Malbec from Bodega Norton

PB#207 - Published March 2019

The skinny on platelets in pregnancy

- platelets: little corks that float around in your bloodstream to plug holes in vessels

- disorders usually present as petechiae, ecchymosis, epistaxis, gingival bleeding, GI bleeding, and AUB (heavy or intermenstrual)

- normal range ~150-400 x 10^9/L

- definition of thrombocytopenia in pregnancy: platelets <150 x 10^9/L

- platelet count decreases as pregnancy progresses

- definition might be arbitrary, as clinically significant bleeding is usually limited to patients undergoing major surgery

- etiology can be categorized as increased platelet destruction or decreased platelet production; in pregnancy? usually the former (immunologic, abnormal activation, or consumption)

DDx: Gestational thrombocytopenia

- most common etiology in pregnancy? gestational (80% of cases)

- underlying pathophysiology not fully understood

- thought to be a combination of hemodilution and increased platelet clearance

- affects 5-10% of pregnant women

- 5 key characteristics:

  1. onset at any time in pregnancy, but usually 2nd or 3rd trimester usually with a platelet count of >75 x 10^9/L

  2. patients are asymptomatic with no history of abnormal bleeding

  3. patients have no history of thrombocytopenia outside of pregnancy

  4. platelet counts usually return to normal within 1-2 months of delivering

  5. incidence of fetal or neonatal thrombocytopenia is low (no specific lab tests to confirm fetal or neonatal thrombocytopenia, however)

DDx: Preeclampsia/HELLP

- accounts for 5-20% of thrombocytopenia in pregnancy

- underlying pathophysiology not fully understood

- thought to be a combination of impaired consumption and activation

- one of the severe features of preeclampsia (<100 x 10^9/L), but close clinical follow-up is recommended if the count drops below 150 x 10^9/L

- hint: sudden onset thrombocytopenia in 3rd trimester should immediately make you think about hypertensive disorders

- clinical hemorrhage uncommon outside of DIC

- if accounted by microangiopathic hemolytic anemia and elevated liver function tests, start thinking about HELLP

- one cross-sectional study suggested neonates may develop thrombocytopenia in pregnancies c/b thrombocytopenia associated w/ preeclampsia/HELLP; but large observational studies haven't supported this claim

DDx: Immunologic etiology

Fetal-neonatal alloimmune thrombocytopenia

- platelet equivalent of hemolytic (Rh) disease of the newborn (though can affect first pregnancy unlike red cell alloimmunization)

- mom develops Ig to fetal platelet antigens (more than 15 specific platelet antigens have been identified, HPA-1a most frequent culprit in severe cases)

- incidence around 1 to 1000-3000

- can occur as early as 20 wga

- affected pregnancies generally have no signs or sx and otherwise indistinguishable features (normal pregnancy, labor/delivery)

- newborn will develop thrombocytopenia within hours of birth: petechiae, ecchymosis, bleeding after circumcision or venipuncture

- most serious complication: intracranial hemorrhage (potentially life-threatening); it occurs in 15% of infants with platelets <50 x 10^9/L

- can also occur in utero, and you have a 50% shot at detecting it with ultrasound (intraventricular, periventricular, or parenchymal hemorrhage)

- evidence of recurrence rates is unclear, and it has been suggested that maternal anti-HPA-1a Ig levels during pregnancy may help identify whether succeeding pregnancies will experience severe fetal thrombocytopenia

Maternal immune thrombocytopenia (ITP)

- maternal IgG can cross placenta and lead to fetal and neonatal thrombocytopenia (25% of cases), though <1% chance of severe hemorrhagic complications in the newborn (i.e. intracranial hemorrhage)

- T-cell mediated, incidence unclear: 1 to 1000-10000 pregnancies affected

- primary ITP: isolated thrombocytopenia in the absence of other etiologies; diagnosis of exclusion (i.e. no pathognomonic signs, sx, or diagnostic tests)

- secondary ITP: culprit is an underlying disease (SLE, APS, infection like HIV and HCV) or drug exposure (heparin, antimicrobials, anticonvulsants, analgesics)

- effect on pregnancy is unclear; no obvious dangers until platelets drop below 50 x 10^9/L (20% risk of postpartum hemorrhage, even w/ treatment)

Other possible etiologies

- splenic sequestration, bone marrow disorders, nutritional deficiencies


- CBC (evaluate for pancytopenia)

- peripheral smear (evaluate for platelet clumping --> pseudothrombocytopenia)

- assays for platelet-associated (direct) Ig and circulating (indirect) antibodies are available but poorly standardized (i.e. these assays can't help you differentiate between ITP and gestational thrombocytopenia)


Gestational thrombocytopenia:

- little or no risk to mom or fetus/newborn

- no need to schedule cesarean delivery or check fetal platelet count

- check platelets when mom presents in labor in order to guide regional anesthesia decision-making (your friendly anesthesiologist will prefer platelets to be >70 x 10^9/L)

- some experts recommend checking a CBC at each routine OB visit (my opinion: individualize)

- check that platelet count has resolved 1-3 weeks postpartum


- same principles as gestational thrombocytopenia

- remain on the lookout for HELLP

- should also resolve postpartum

- hemorrhage during delivery is uncommon, but expect operative site oozing like that seen in c-section

- platelet transfusion may be beneficial if count is <50 x 10^9/L, though will likely quickly drop again due to increased intravascular destruction

- ACOG: transfuse platelets to improve count to >50 x 10^9/L if cesarean delivery is indicated

- note on HELLP: steroids or uterine curettage may lead to improvement of thrombocytopenia, but no differences have been noted in maternal mortality or morbidity with these treatments

Maternal Immune thrombocytopenia

- no evidence for specific platelet threshold target through treatment, but treatment should be initiated when counts fall <30 x 10^9/L, patient experiences symptomatic bleeding, or to boost to >50 x 10^9/L for anticipated cesarean delivery

- again, consider regional anesthesia preclusions re: platelets (ideally count is >70 x 10^9/L)

- treatment: corticosteroids, IVIG, or both

- steroids, 1st line: prednisone 0.5-2 mg/kg for up to 21 days; can start low (10-20 mg/day) and up-titrate; initial response will be seen in 4-14 days w/ peak response in 1-4 weeks

- IVIG, 2nd line: one-time dose of 1g/kg (can be repeat if necessary); initial response will be seen in 1-3 days w/ peak response in 2-7 days ($$$)

- splenectomy is also an option in refractory patients; expect prolonged remission at 1 year or longer in many patients

- platelet transfusion: temporizing measure at best, effects are short-lived; give "a larger-than-usual dose (twofold to threefold) of platelets with intravenous high-dose corticosteroids or IVIG ranging from every 30 minutes to 8 hours"

- some experts recommend checking platelet count in every trimester in future pregnancies in asymptomatic women w/ ITP, but there is little evidence to provide such guidance

- generally best to avoid NSAIDs, aspirin, and trauma (duh)

- although cases of fetal and neonatal thrombocytopenia are rare in maternal ITP, therapeutic efforts have been devised to prevent them; none have panned out in the literature

- procedures in labor associated with increased hemorrhagic risk should be avoided (i.e. fetal scalp electrodes or vacuum assisted delivery)

- reserve intramuscular injections (e.g. Vitamin K) and elective newborn procedures (e.g. circumcision) until platelet count is known

- remember: platelet nadir is generally seen between days 2 and 5 of life

Fetal-neonatal alloimmune thrombocytopenia

- suspect if you see significant fetal or neonatal intracranial bleeding (ultrasound) or neonatal hemorrhage

- get labs: determination of HPA and zygosity of both parents

- CVS has been recommended by some experts, though others have expressed caution due to the potential for increase sensitization in cases in which the fetus is affected

- get MFM involved, as this process can be convoluted and ambiguous

- no indirect methods to determine fetal platelet count; outcomes of previously affected siblings aren't reliably predict of outcomes in present pregnancy

- optimal management remains uncertain, but close follow-up by obstetrics is recommended as well as early involvement of pediatrics in the patient's prenatal course

- IVIG +/- steroids has not been found to be effective in all cases, and it's at least as effective as intrauterine platelet transfusions in preventing fetal and neonatal bleeding complications

- maternal platelet transfusion is effective in bumping fetal platelets; however, platelets are short-lived, so weekly platelet transfusions would be required, and this may also worsen alloimmunization

- fetal blood sampling should be reserved to 32 wga and only recommended to women planning to deliver vaginally; the purpose is to evaluate platelet response to therapy in order to optimize safety of vaginal delivery, yet it's late enough to deliver a viable newborn in the event that a complication arises from sampling that requires emergent delivery

- c-section is recommended for newborns with platelet count <50 x 10^9/L

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