Survival of twins after delivery depends upon various factors. What is the commonest cause of perinatal moality in twins?
**Core Concept**
The commonest cause of perinatal mortality in twins is related to the increased risk of complications associated with premature birth and low birth weight, particularly in monochorionic-diamniotic (MoDi) twins. Monochorionicity refers to the sharing of a single placenta by the twins, which can lead to various complications.
**Why the Correct Answer is Right**
The correct answer is related to the increased risk of respiratory distress syndrome (RDS) and other complications associated with prematurity. Premature birth is a major risk factor for perinatal mortality in twins, especially in those born before 32 weeks of gestation. Monochorionicity is a significant contributing factor to premature birth, as it can lead to unequal sharing of nutrients and oxygen between the twins, resulting in growth restriction and preterm labor.
**Why Each Wrong Option is Incorrect**
**Option A:** While preterm birth is a significant risk factor for perinatal mortality in twins, it is not the most common cause. Preterm birth is a consequence of various factors, including monochorionicity, but it is not the underlying cause.
**Option B:** Intrauterine growth restriction (IUGR) is a significant risk factor for perinatal mortality in twins, particularly in monochorionic-diamniotic twins. However, it is not the most common cause of perinatal mortality.
**Option C:** Polyhydramnios, or excessive amniotic fluid, is a complication that can occur in twins, particularly in monochorionic-diamniotic twins. However, it is not the most common cause of perinatal mortality.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that monochorionicity is a significant risk factor for perinatal mortality in twins, particularly in those born before 32 weeks of gestation. This is due to the unequal sharing of nutrients and oxygen between the twins, leading to growth restriction and preterm labor.
**Correct Answer: B. Intrauterine growth restriction (IUGR)**