Which condition is characterized by a platelet count of less than 150,000/L during pregnancy?

The appropriate condition characterized by a platelet count of less than 150,000/L during pregnancy is gestational thrombocytopenia. This condition is defined specifically by a reduction in platelet numbers that often manifests after the first trimester. It occurs in about 5-7% of pregnancies and is typically mild and benign, resolving postpartum without treatment.

In gestational thrombocytopenia, the low platelet count is often a result of increased blood volume, dilution effects, and the increased consumption of platelets during pregnancy; it generally does not lead to significant bleeding or complications unless the count becomes extremely low.

The other conditions listed do not primarily involve thrombocytopenia. Gestational diabetes is related to glucose metabolism and insulin resistance, gestational hypertension pertains to elevated blood pressure without proteinuria, and preeclampsia involves hypertension and potential organ dysfunction, including low platelets, but is defined by more severe clinical criteria than just low platelet count. Thus, gestational thrombocytopenia is correctly identified as the condition marked by a platelet count below the normal threshold during pregnancy.