Twin pregnancy: What multiples mean for mom

A twin pregnancy takes special care. Know what to expect during your twin pregnancy, from nutrition and weight gain to possible complications. By Mayo Clinic Staff

Would you be surprised to learn that you're carrying twins or even triplets?

Sometimes a twin 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 boosts the odds of twins or other multiples.

If you're diagnosed with 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

Fraternal twins — the most common kind — 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. Genetically, they're no more alike than any other siblings.

Identical twins occur when a single fertilized egg splits and develops into two fetuses. Identical twins might share a placenta, but each baby usually has a separate amniotic sac. 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

Your health care provider might suspect a twin pregnancy if your uterus is larger than normal or there seems to be more than one fetal heartbeat. A suspected twin pregnancy is typically confirmed with 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.

Dec. 14, 2011 See more In-depth