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Twin pregnancy: What multiples mean for mom
Twin pregnancy? Taking good care of yourself is the best way to take care of your babies. Here's what you need to know.
By Mayo Clinic staffWould you be surprised to learn that you're carrying twins or even triplets? It happens to an estimated three in every 100 pregnant women in the United States. Worldwide rates of twin pregnancy vary. One thing is certain, however: Twin pregnancy rates are on the rise.
What's driving the twin pregnancy trend?
Many women are delaying pregnancy well into their 30s and beyond — when age-related hormonal changes may cause more than one egg to be released at a time. This boosts the odds of conceiving nonidentical (fraternal) twins.
Because of their decreased fertility, older women are also more likely to use assisted reproductive technologies — such as in vitro fertilization — to conceive. Since these procedures typically involve implanting more than one fertilized egg in the uterus, they're more likely to result in twins or other multiples.
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 may 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 look exactly alike. 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
Typically, a twin pregnancy is diagnosed before delivery. The first clue is often a uterus that's larger than normal or more than one fetal heartbeat. Certain blood tests may suggest twins or other multiples as well.
A suspected twin pregnancy is often 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.
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