Infertile couples often use in vitro fertilization (IVF) to increase their chance of having a baby. It is known that IVF also increases their chance of having twins or triplets.

Couples considering IVF usually seek facilities that have a higher "probability of successful birth". Some facilities calculate the "probability of successful birth" as the number of babies born divided by the number of women who receive the IVF therapy. Is this probability calculated correctly?

No. Their calculation is wrong, because they need to use the number of women who receive the therapy divided by the number of babies born.

No. Their calculation is wrong because some women may have more than one baby born. For example, if all women successfully gave birth, but some women had twins, then the calculated "probability of success" would exceed 1, and not be a valid probability.

Yes. The calculation is totally accurate.