In Primi, in Preterm Labour, which of the following can be used as Tocolytic a) Ritodrineb) MgSo4c) Dexamethasoned) Propranolol

**Core Concept**
The question tests the student's knowledge of **tocolytic agents** used in managing preterm labor, specifically in primigravidas. Tocolytics are medications used to suppress premature uterine contractions.

**Why the Correct Answer is Right**
**MgSO4 (Magnesium sulfate)** is commonly used as a tocolytic agent to inhibit uterine contractions in preterm labor. It works by blocking calcium channels in the uterine muscle, thus reducing the frequency and intensity of contractions.

**Why Each Wrong Option is Incorrect**
**Option A:** Ritodrine, a beta-2 adrenergic agonist, was once used as a tocolytic but is no longer recommended due to side effects.
**Option C:** Dexamethasone is a corticosteroid used to promote fetal lung maturity, not as a tocolytic.
**Option D:** Propranolol is a beta-blocker used for various cardiovascular conditions, not for tocolysis.

**Clinical Pearl / High-Yield Fact**
Remember, **MgSO4** is not only used for tocolysis but also for neuroprotection in preterm infants and as an anticonvulsant in preeclampsia.

**Correct Answer:** B. MgSO4