Twin pregnancy: What twins or multiples mean for mom

Being pregnant with multiples takes special care. Know what to expect, from nutrition and weight gain to possible complications.

By Mayo Clinic Staff

If you're having a twin pregnancy or other multiples, here's what you need to know to take good care of yourself — and your babies.

How multiples are made

Sometimes a twin or triplet pregnancy just happens. In other cases, specific factors are at play. For example, a twin pregnancy is more likely as you get older because hormonal changes can cause more than one egg to be released at a time. Use of assisted reproductive technologies — such as in vitro fertilization — also increases the odds of twins or other multiples.

Fraternal twins — the most common kind of twins — occur when two separate eggs are fertilized by two different sperm. Each twin has his or her own placenta and amniotic sac. The twins can be two girls, two boys, or a boy and a girl.

Identical twins occur when a single fertilized egg splits and develops into two fetuses. Identical twins might share a placenta and an amniotic sac or the twins might share a placenta and each have separate amniotic sacs. Genetically, the two babies are identical. They'll be the same sex and share physical traits and characteristics. Rarely, identical twins fail to completely separate into two individuals. These babies are known as conjoined twins.

Triplets and other higher order multiples can be identical, fraternal or a combination of both.

Diagnosing a twin pregnancy

Most twin or multiple pregnancies are discovered during an ultrasound. During this exam, sound waves are used to create images of your uterus and baby — or babies.

Sometimes a seemingly normal twin pregnancy is later found to have only one baby. This is known as vanishing twin syndrome. Such an episode can be heartbreaking, frustrating and confusing. Often, there's no clear explanation for the loss.

Feb. 14, 2018 See more In-depth