According to Hellin’s law chances of twins in pregnancy are :
**Core Concept**
Hellin's law describes the relationship between the frequency of dizygotic (fraternal) twins and the frequency of single births in a population. This law is used to estimate the probability of twinning based on the incidence of single births.
**Why the Correct Answer is Right**
Hellin's law states that the frequency of dizygotic twins is inversely proportional to the frequency of single births. This means that in populations with a higher frequency of single births, the chances of dizygotic twins are lower. The law is expressed as: frequency of dizygotic twins = 1 / (3 * frequency of single births). This law is useful for predicting the likelihood of twinning in different populations.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Hellin's law specifically relates to dizygotic twins, not monozygotic (identical) twins.
**Option B:** This option is incorrect because Hellin's law does not take into account the frequency of monozygotic twins.
**Option C:** This option is incorrect because Hellin's law is a statistical relationship and does not provide a direct numerical value for the probability of twinning.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that Hellin's law is a population-based estimate and may not accurately predict the likelihood of twinning in individual cases. Additionally, the law does not account for other factors that may influence twinning rates, such as family history or assisted reproductive technologies.
**Correct Answer:** C.