An abnormally high number of platelets in pregnancy is far less common than low platelet levels. High platelet levels are either essential, or primary, meaning that an excess of platelets are being made in the bone marrow. Reactive, or secondary, platelet levels mean that another disease process, such as inflammation or cancer, is causing an increase in platelets, the Cleveland Clinic explains. High platelet levels caused by primary thrombocytosis, also known as thrombocythemia, can be dangerous in pregnancy and can result in serious maternal and fetal complications.
Pregnancy loss occurs frequently in women with essential thrombocytosis, a case history by lead author Gokhan Anil, MD reports in The Female Patient. Women with essential disease have a miscarriage rate of 43 percent, 36 percent in the first 3 months of pregnancy, according to Anil. Stillbirth may occur in 5 percent of cases. Medications given in pregnancy to prevent pregnancy loss include low-dose aspirin and medications that decrease platelet production. Some platelet-lowering medications, such as anagrelide, busulfan and hydroxyurea, is embryo-toxic and should not be used in pregnancy.
Intrauterine Growth Retardation
Fetal intrauterine growth retardation (IUGR) complicates approximately four percent of pregnancies in women with essential thrombocytosis, Anil states. Babies with IUGR have weights that are in the tenth percentile or less, and appear thin, wasted and pale, the University of Virginia explains. They may have low oxygen and blood sugar levels at birth and may have trouble maintaining their temperatures. Severe IUGR can lead to intrauterine death.
Preterm delivery, or delivery before 37 weeks of pregnancy, occurs in eight percent of cases of thrombocytosis in pregnancy, according to Anil. Possible causes of preterm delivery include preeclampsia, a complication of pregnancy characterized by maternal high blood pressure, protein in the urine and fluid retention, which affects four percent of women with thrombocytosis. Placental abruption, where the placenta separates prematurely from the uterine wall, is also a possible complication of thrombocytosis, according to the Mayo Clinic. Abruption usually requires immediate delivery or severe maternal and fetal hemorrhage can occur.