Final answer:
While the exact probability of a multiple birth from an ART cycle is not provided, it is suggested that historically, multiple embryo transfers increased the likelihood of multiples. However, recent limitations on the number of transferred embryos aim to lower this risk.
Step-by-step explanation:
The probability of an assisted reproductive technology (ART) cycle resulting in a multiple birth is not explicitly given in the information provided. However, it is mentioned that hormonal treatments for infertility can result in multiple eggs being ovulated, increasing the chances of conceiving twins, triplets, or higher-order multiples. Historically, with in vitro fertilization (IVF), the transfer of multiple embryos was common to ensure a greater chance of pregnancy, which led to higher probabilities of multiple births. Nowadays, regulations limit the number of embryos transferred to reduce the chance of multiples. Therefore, while we don't have a specific probability from the provided text, we understand that multiple births are more likely with certain ART procedures, especially if multiple embryos are transferred.
It is also important to note that the risk of having multiples is balanced against the risk of premature births and developmental problems. With current regulations and improved implantation success, the intentional transfer of multiple embryos is less frequent, hence reducing the probability of multiple-birth pregnancies resulting from ART cycles.