At one point in their lives many women have an immense desire to get pregnant. And when they finally are pregnant they might be well surprised: suddenly the doctor explains that you are expecting twins.
Multiple births are still rare but in the last decades a slight increase could be noted. Reasons are mainly the increase of in vitro fertilizations and hormonal treatments.
In those families where multiple births already happened to be there is an increased probability for the parents-to-be to conceive twins.
But also the age of the woman plays a vital role: the older the woman the higher the probability to deliver twins. One explanation is the fact that –with increasing age- the female body produces more hormones that initiate the ovulation. Therefore it might even happen that the ovaries release several ovocytes at one and the same time.
One distinguishes between identical and non-identical twins. Here, the probability to conceive non-identical twins is three times as high as to give birth to identical twins. The chance to deliver identical twins is 1:300.
Identical twins develop out of a fertilized ovocyte which separates in two different germ layers. In contrast to non-identical twins the identical twins always have the same gender and share identical genes.
Non-identical twins develop out of the fertilization of two egg cells. The babies grow separated from each other in two different amniotic cavities and placentas. The gender of the non-identical twins can differ and they have similar genes just like “ordinary” siblings.
Signs for multiple births cannot only be recognized by the doctor. Also the body of the mother-to-be might disclose it: the uterus is much bigger than it should be, adequate to the stage of pregnancy, and the abdominal girth and weight of the mother-to-be are increasing rapidly.
As multiple births are always considered as risky pregnancies the majority of women decides to deliver with the help of a C-section.