Finding out that you are expecting not one but two or more children can be overwhelming. 

Twins Are Not Always Identical

A twin pregnancy can result from chance or be caused by precise factors, such as hereditary factors on the maternal side, the mother’s age, or assisted fertilization techniques

The most common is a dizygotic or dichorionic twin pregnancy, when two separate eggs are fertilized by two different sperm. In this case, each fetus has its own placenta and amniotic sac.

In a dizygotic twin pregnancy, the twins have a different genetic heritage and have two separate placentas. Therefore, two boys, two girls, or one boy and one girl can be born, and they will be different from a physical aspect. 

Monozygotic or monochorionic twin pregnancy occurs when one egg is fertilized by one sperm and then divides into two separate zygotes, from which two different embryos will be formed. Identical twins typically have their own amniotic sac and umbilical cord but share a placenta. They will have the same sex and exhibit very similar physical traits. A monochorionic twin pregnancy can be diamniotic – where the twins are in two separate sacs, or, more rarely, monoamniotic, where the twins are in the same sac.

Monochorionic diamniotic twin pregnancy is a risk condition for certain complications (such as feto-fetal transfusion) that require frequent ultrasound evaluations – twice a week from 15 weeks onward – and sometimes a utero (laser) treatment.

Twin Pregnancy

Twin pregnancy requires more follow-up than a single pregnancy. Typically, during the first-trimester ultrasound, a woman discovers she is expecting twins (or more), although detection may be earlier. As early as 12 weeks, it is possible to know whether they are dizygotic or monozygotic twins. 

It is essential to distinguish whether the pregnancy is dichorionic or monochorionic, as the following treatment might differ.

Monochorionic twin pregnancy should be monitored with ultrasound checks twice weekly due to the high risk of complications. Ultrasound is the only technique to check for complications such as feto-fetal transfusion requiring laser treatment in utero.

More frequent check-ups may be needed to monitor proper fetal growth.

Possible Complications

Compared with “classic” pregnancy, women expecting twins run a higher risk of hypertension or high blood pressure

If this is associated with the presence of protein in the urine, we call it pre-eclampsia. This condition should not be underestimated to protect the well-being of the mother and her baby. 

Twin pregnancies rarely reach the expected delivery date, and preterm delivery is more common than single pregnancies. Depending on the week the labor is induced or when delivery is necessary due to other complications, the mother and baby will require specific care or neonatal care in specialized units.

Natural or Cesarean Delivery

In most cases, delivery is by Cesarean section, although natural delivery can be approached if the first baby is in a cephalic position – with its head down.

In case natural delivery is initiated and complications arise, it may be necessary to switch to Cesarean section, but this can also happen in single pregnancies