Pregnancy Information Multi Births

Twins, triplets, and multiple births are not complications of pregnancy, of course, but any pregnancy that involves twins or multiple births is considered complicated. Certain risks to both the pregnant woman and fetuses increase with a multiple pregnancy, including premature birth and preeclampsia.

Factors that Increase the Odds of Multiple Births

Since the 1980s, the incidence rates for twins, fraternal twins or triplets have increased 74 percent in the United States. Three percent of children born in America are the result of multiple births.

Two reasons are suspected for this dramatic increase in multiple births. First, the average age of pregnant women in the U.S has increased since the 1980s. Increased use of fertility drugs and in vitro fertilization has been linked to the rise in triplets and other multiple births.

A pregnant woman’s chance of a pregnancy with twins increases if she has a personal or family history of twins. Pregnant women who are obese also seem to have a greater likelihood of twins or triplets.

Identical Twins vs. Fraternal Twins

If you’re pregnant with twins, they’ll be either identical or fraternal. Identical twins are monozygotic twins: the result of a single fertilized egg that splits in two. Identical twins share gender and the same genetic profiles.

Fraternal twins occur when two separate eggs are fertilized. Known medically as dizygotic twins, fraternal twins need not share gender, have different genetic profiles and may not necessarily even look alike. Triplets and other multiple births share the same features as fraternal twins.

Risks Associated with Multiple Births

Multiple births increase the risk of pregnancy complications. A pregnant woman carrying twins or triplets is more likely to develop gestational diabetes, hypertension, hemorrhage and preeclampsia. Preeclampsia is a type of hypertension, often accompanied by edema and proteinuria. One third of all pregnant women carrying twins develop preeclampsia during their pregnancy.

Fetal Risks

Multiple fetuses have an increased risk of birth defects and developmental disorders. Mental retardation, cerebral palsy, vision difficulties and hearing loss are all more common in multiple births than in single births. Due to the increased risk of premature births, twins and triplets are more likely to have low birth weights.

Twin-to-Twin Transfusion

Twins sharing the same placenta may experience a complication known as twin-to-twin transfusion. Twin-to-twin transfusion occurs when the twins share blood vessels within the placenta. As a result, one of the twins receives far more nutrients and blood than the other.

Identical twins are much more likely to develop twin-to-twin transfusion than fraternal twins, as identical twins are more likely to share a single placenta. Fifteen percent of identical twins develop twin-to-twin transfusion.

By thirty weeks, one twin will be noticeably larger than the other. Twin-to-twin transfusion places both twins under severe stress: while one fetus receives insufficient nutrition, the other receives far too much.

Treatment options for twin-to-twin transfusion include laser surgery to seal the twins’ blood vessel connections, and amniocentesis to drain away excess amniotic fluid. With proper treatment, sixty percent of twins who experience twin-to-twin transfusion survive.

Premature Birth

Prematurity is a common pregnancy complication for multiple births. Sixty percent of identical and fraternal twins are delivered prematurely, and triplet pregnancies end prematurely in ninety percent of cases. Pregnancies with more then three infants almost always end before term.

This tendency towards prematurity in multiple births places the infants at greater risk of fetal respiratory distress and other complications of premature birth. Accordingly, a pregnant woman carrying twins or triplets must work closely with medical professionals to ensure that the pregnancy ends as close to term as possible.

Detecting Multiple Births

The presence of twins or triplets may be detected in a number of ways. Ultrasound may reveal more than one fetus or it may detect more than one fetal heartbeat. Unusual blood tests may also suggest twins or triplets.

An unusually rapid increase in uterine size suggests the possibility of twins. Pregnant women carrying twins or triplets may experience particularly severe morning sickness. If a pregnant woman has given birth to a single child in a previous pregnancy, she may detect an unusual level of fetal movement if she has twins.

Preparing for Multiple Births

Twins, triplets and other multiple births require more prenatal visits and monitoring than a “normal” pregnancy. The pregnant woman must get sufficient nutrition (which can be difficult with twins), and watch for possible signs of premature labor. With care and attention, multiple births can produce healthy babies.


Beers, M. H.