Which pregnancy condition is most likely to occur during the 2nd trimester?

The most likely pregnancy condition to occur during the 2nd trimester is preeclampsia. This condition typically presents after the 20-week mark of gestation, making it a common concern during the second trimester. Preeclampsia is characterized by high blood pressure and often involves additional symptoms such as protein in the urine. Its onset during this period aligns with the physiological changes and stressors that the mother's body undergoes as the pregnancy progresses.

The other conditions listed tend to arise at different stages of pregnancy or have distinct risk factors. Abruptio placenta, for instance, is usually associated with the later stages of pregnancy and can be prompted by trauma or other factors influencing placental detachment. Similarly, placenta previa also tends to be diagnosed later in the pregnancy, particularly as the cervix begins to efface and dilate closer to term. Ovarian torsion is not directly related to pregnancy and can occur at any time, often unrelated to the gestational period. Therefore, preeclampsia's characteristic development and timing make it the most relevant condition in the context of the second trimester.