**Core Concept**
The question tests the ability to diagnose a condition in a pregnant woman presenting with symptoms of excessive vomiting, bleeding per vaginum, and a uterus size larger than expected for the gestational age. This requires an understanding of the pathophysiology and clinical presentation of various obstetric complications.

**Why the Correct Answer is Right**
The patient's presentation is highly suggestive of a molar pregnancy. Molar pregnancy, also known as hydatidiform mole, is a gestational trophoblastic disease characterized by the abnormal proliferation of trophoblastic cells. This leads to the formation of a non-viable embryo and an excessive production of human chorionic gonadotropin (hCG), which can cause excessive vomiting. The ultrasound findings of a uterus size larger than expected for the gestational age, combined with the presence of vaginal bleeding, are typical of a molar pregnancy. The high levels of hCG can also cause hypertension, which is consistent with this patient's blood pressure reading.

**Why Each Wrong Option is Incorrect**
**Option A:** Gestational hypertension typically presents with hypertension and proteinuria, but not typically with excessive vomiting or a uterus size larger than expected for the gestational age.

**Option C:** Polyhydramnios is characterized by an excessive amount of amniotic fluid, which is not consistent with this patient's presentation of vaginal bleeding and a uterus size larger than expected for the gestational age.

**Option D:** Antepartum hemorrhage can present with vaginal bleeding, but it does not typically cause excessive vomiting or a uterus size larger than expected for the gestational age.

**Clinical Pearl / High-Yield Fact**
Molar pregnancy is a rare but potentially life-threatening condition that requires prompt diagnosis and treatment. It is essential to consider this diagnosis in any pregnant woman presenting with excessive vomiting, vaginal bleeding, and a uterus size larger than expected for the gestational age.

**✓ Correct Answer: B. Molar pregnancy**