The probability of having twins is 1 in 40. That means there are over 70,000,000 in the world. The twins, a mystery not yet fully understood.
- Multiple pregnancies increase the risk of preeclampsia, gestational diabetes, and postpartum hemorrhage.
- Pregnancy symptoms are sometimes accentuated in multiple pregnancies.
20,000 twins are born each year in France. 6 times out of 10 – we don’t know why – they will be of the same sex.
Two types of twins
There are two types of twins. The real ones: the mother’s egg, fertilized by a spermatozoon, divides into 2, which leads to the development of 2 separate embryos. The two children are exact replicas of each other and their possible future physical differences will be due to external non-genetic factors.
When the mother releases two eggs, each fertilized by a spermatozoon, we will then speak of fraternal twins. They are two different children who will develop at the same time in the womb of the mother. Their differences will be apparent fairly quickly, even if they are bred similarly.
Two different placentas
False and some identical twins develop in two different placentas. The pregnancy, even if it is cumbersome, and the delivery, often by caesarean section, go rather well. This is not the case when identical twins are in a single pouch, as an imbalance occurs that can favor one fetus over the other. In very rare cases, one of the twins may even be fed through the placenta through the other. For the prognosis of possible prematurity, it is essential to find out the number of placentas, which ultrasound can do very well, long before birth.
Siamese
When identical twins have an egg that separates badly, then we speak of conjoined twins. Nowadays, it is an exceptional event, one birth for 75,000, which still represents 20 Siamese a year in France. In the majority of cases, these are also little girls who will benefit from surgical separation, unless these Siamese have vital organs in common. However, such tragedies can now be avoided thanks to ultrasound, which diagnoses twin pregnancy in the first trimester.
Why so many twins?
We talked about microclimates, twice as many twins in the north of France as in the south-west. Age, over 37 for the mother, also seems to be a contributing factor, but today the main source of twins, triplets, quadruplets, or even more, is found in in vitro fertilization methods.
