Final answer:
The medication that the nurse practitioner would discontinue immediately for a pregnant patient among those listed is losartan (Cozaar) due to its potential for fetal harm.
Step-by-step explanation:
A pregnant patient with medical conditions such as obesity, diabetes, and hypertension requires careful consideration of medication safety during pregnancy. The use of losartan (Cozaar), an angiotensin II receptor antagonist, is contraindicated during pregnancy due to the potential for fetal harm. Therefore, among the listed medications, losartan would be discontinued immediately upon confirmation of pregnancy.
Metformin is often continued during pregnancy for women with type 2 diabetes, as it is generally considered safe and can help control blood glucose levels. Methyldopa has a longstanding history of use for hypertension in pregnancy. Sumatriptan (Imitrex), a medication for migraines, may be used during pregnancy if the benefits outweigh the risks, but this decision is made on a case-by-case basis.