Thrombocytopenia, a low platelet count, is the second most common blood disorder in pregnancy, affecting 8 percent of pregnancies, according the Journal of the American Board of Family Medicine article "Thrombocytopenia in Pregnancy." Platelets are blood cells that help blood clot. The normal range is 150,000 to 450,000 platelets per microliter, a count between 100,000 and 150,000 is mildly decreased and 50,000 to 100,000 is a moderate drop. Platelet counts under 50,000 are very low, and spontaneous bleeding may occur. Several disease processes in pregnancy cause thrombocytopenia.
Gestational Thrombocytopenia
Gestational thrombocytopenia causes 75 percent of low platelet counts in pregnancy, according to "Thrombocytopenia in Pregnancy" authors Jeffrey Levy, CPT, MC, and Lance Murphy, M.D. With this condition, platelet count is usually above 70,000 platelets per microliter, and fetal platelet count is usually normal. Gestational thrombocytopenia usually causes no symptoms and poses no risk to mother or fetus. Platelet levels usually return to normal within three months after delivery. The cause of gestational thrombocytopenia is unclear, but it may be related to the increased blood volume in pregnancy.
Idiopathic Thrombocytopenia (ITP)
ITP is an autoimmune disorder that comprises 4 percent of cases of thrombocytopenia in pregnancy. Platelets are destroyed by antibodies, which can cross the placenta and decrease fetal platelet count, although this is rare, the Merck Manual states. It occurs in 12 to 15 percent of babies, according to Dr. Eric Rose, professor of hematology at the University of Washington.
Levy and Murphy explain that pregnant women who develop ITP often have mildly decreased platelet counts before pregnancy. Corticosteroids may be given to suppress the immune response, but this can cause fetal intrauterine growth retardation. Platelet infusion or spleen removal may be necessary in some cases.
Pregnancy Induced Hypertension (PIH) / HELLP
PIH, also known as pre-eclampsia, is thought to be a pregnancy mediated immune response that causes hypertension, protein in the urine, edema and, in some cases, low platelet count. PIH accounts for approximately 21 percent of cases of thrombocytopenia in pregnancy, Levy and Murphy note. Medication to control blood pressure may be given, but the cure for PIH is delivery.
HELLP stands for hemolysis, elevated liver enzymes, low platelets, and the syndrome is usually a complication of PIH, affecting 4 to 12 percent of PIH cases. HELLP is a life-threatening complication, with a maternal rate of 1 to 4 percent, Rose states. The liver can rupture, causing severe hemorrhage.
Neonatal Alloimmune Thrombocytopenia
Neonatal alloimmune thrombocytopenia occurs when fetal platelets are attacked by maternal antibodies that cross the placenta. Levy and Murphy state that neonatal alloimmune thrombocytopenia is similar to Rh disease, except that it destroys platelets rather than red blood cells. The disease usually isn't diagnosed until after delivery, when bruising or petechiae, small red pinpoint hemorrhages in the skin, occur. Intracranial hemorrhage occurs in 10 to 20 percent of infants.
References
- "Journal of the American Board of Family Medicine"; Thrombocytopenia in Pregnancy; Jeffrey Levy, CPT, MC, Lance Murphy, M.D.; 2002
- University of Washington: Causes of Thrombocytopenia
- University of Washington: Idiopathic Thrombocytopenic Purpura
- University of Washington: Hypertensive Diseases of Pregnancy
- Merck Manual: Autoimmune Diseases of Pregnancy
