Approximately one third of triplet gestations are complicated by thrombocytopenia, one half of which are severe. This represents a much higher frequency as compared with the 6.6% to 11.6% that was reported for singleton gestations. Hypertension-associated disorders of pregnancy account for 71.7% of thrombocytopenia in triplets, unlike singleton gestations in which 75% of thrombocytopenia is gestational. The single most common cause of thrombocytopenia in triplets is severe preeclampsia. This is the first study to evaluate the incidence and cause of thrombocytopenia in a large set of triplet gestations.