Twin and Multiple Birth Rate

Multiple birth rates for 2006 were released in January 2009. Here are some highlights:

Twin Birth Rate

The 2006 twin birth rate was 32.2 per 1,000. This remained unchanged from 2005 and 2004.

The number of live births in twin deliveries rose 3 percent between 2005 and 2006 to 137,085 births. This number has more than doubled since 1980 (from 68,339).

• 137,085 twins were born in 2006
• The twin birth rate in 2006 was 32.2 per 1,000 births

Higher Order Multiples

The rate of triplet and higher order multiple births (quadruplets, quintuplets, sextuplets and septuplets) continued to decrease in 2006. The 2006 rate was 153.3 per 100,000 births compared to 161.8 in 2005 and 176.9 in 2004.

In 2006, the number of higher order multiple deliveries were:

• 6,118 triplets
• 355 quadruplets
• 67 quintuplets
• 0 sextuplets or septuplets

Multiple Birth Death Rates

Twins are five times more likely than singletons to die within a month of birth. Triplets are nearly 15 times more likely to die within a month of birth. (From 2005 data.)

Twinning Rates by Race

Twinning rates were essentially unchagned among the three largest racial/origin groups:

• Non-Hispanic White: 36.0 per 1,000
• Non-Hispanic Black: 36.8 per 1,000
• Hispanic: 21.8 per 1,000

Impact of Fertility Treatments

Assisted reproducive therapies (including in vitro, ovulation-inducing drugs and artificial insemination) account for 17 percent of all twins and 40 percent of all triplets born in 2004.

• 17 percent of twins are the result of fertility treatments.
• 40 percent of triplets are the result of fertility treatments.

Maternal Age Factors

Older women are much more likely to give birth to twins or triplets. One of every five births to women 45 years of age and older was born in twin delivery compated with less than two of every 100 births to mothers 20-24 years of age.

• 20 percent of births to women over age 45 were twins.
• Only 2 percent of mothers 20-24 years of age had twins.

Preterm Birth Rates

A trend towards shorter pregnancies with multiples was observed. The percentage of twins delivered preterm (prior to 37 weeks) rose to 60.4% in 2006. This compares to 11.1% for single birth babies.

• Less than 40% of twins were born at 37 weeks or later.
• More than 12% were born prior to 32 weeks gestation.
• 36.33% of triplets were born prior to 32 weeks.
• About 80% of quads and higher were born befoer 32 weeks.

Highest and Lowest Multiple Birth Rates By State

For the years 2004- 2006, twins accounted for more than 4 percent of all births (more than 40 per 1,000) in Massachusetts, Connecticut and New Jersey. New Jersey, Nebraska and Massachusetts also recorded the highest rates of higher order multiple birth (triplets or more). The lowest rates were reported in New Mexico.

• States with the highest multiple birth rates are Connecticut, Massachusetts, New Jersey and Nebraska.
• State with the lowest rate is New Mexico.

Source: National Vital Statistics Reports, Vol 57. No. 7, January 7, 2009