In the past, the birth of twins or triplets wasn’t that common, so no clinical guidelines for managing multiple pregnancies existed. But now, a true need has arisen, so specific protocols for multiples are followed in most places.
Are there more twins now in the world?
Yes. Since 1980, the number of twin pregnancies has increased by 75%, and triplets have gone up even more [1].
Why are twins and triplets more common than before?
Higher numbers of twin and triplet pregnancies are mainly due to modern fertility treatment methods. For example, if a woman takes medication to stimulate ovulation, there is a higher chance of more than one egg maturing and fertilizing in a single cycle.
Currently, the consensus among experts is to transfer only one embryo at a time. However, in patients who have experienced multiple failed transfers, doctors may implant two embryos into the uterus at a time in an attempt to increase the chances of pregnancy. If both embryos were to implant successfully, the result would be a twin pregnancy [2].
What is the probability of conceiving twins naturally?
With natural conception, the probability of having twins is about 1 in 250 pregnancies and the chance of having triplets is 1 in 10,000. However, between the ages of 35 and 40, the probability of multiple pregnancies increases because women at this age (called the "late fertile stage") can have two or three oocytes mature simultaneously in a given cycle [1]. Nowadays, many women postpone having children, and this too increases the number of twins being born globally.
If one of the future parents is a twin, does the chance of having a multiple pregnancy increase?
There is a genetic pattern when it comes to twins. However, the tendency for multiple pregnancies is mostly passed on through the mother. So if the expectant mother is a twin herself, the probability of her having twins increases from 1:250 to 1:60 [1].
