Twin Birth Rate
The 2009 twin birth rate in the United States was 33.2 per 1,000. This is up very slightly from 2008, when the twin birth rate was 32.6 per 1,000, a continued increase from 2007 when the twin birth rate was 32.2 per 1,000. The twinning rate rose sharply between 1980 and 2004 (from 18.9 to 32.2) but has been fairly stable in the years since.
In 2009, 137,217 infants were born in twin deliveries. This number is down slightly from 2008 (138,660) and 2007 (138,961). This number mirrors the decrease in overall births in the United States, which declined about 3%.
- 137,217 twins were born in 2009
- The twin birth rate in 2009 was 33.2 per 1,000 births.
- 138,660 twins were born in 2008
- The twin birth rate in 2008 was 32.6 per 1,000 births.
- 138,961 twins were born in 2007
- The twin birth rate in 2007 was 32.2 per 1,000 births.
- 137,085 twins were born in 2006
- The twin birth rate in 2006 was 32.2 per 1,000 births.
Higher Order Multiples
Overall, the rate of triplet and higher order multiple births (quadruplets, quintuplets, sextuplets and septuplets) was slightly increased in 2009, but still down from numbers found in 2007 and earlier. The 2009 rate was 153.5 per 100,000 births, compared to 147.6 per 100,000 births in 2008, 148.9 in 2007, 153.5 in 2006, 161.8 in 2005 and 176.9 in 2004. The number of triplets born in 2009 increased slightly from 2008 (5,905 from 5,877) but down from 2007 (5,967) and 2006 (6,118). The number of quadruplet and higher order multiple births also increased. Quadruplets: 355 in 2009 (345 in 2008, but 369 in 2007). The number of quints (or higher) almost doubled from 2008. 80 born in 2009, but 46 born in 2008, However, the rate is still down from 91 quints or higher in 2007, and only 67 in 2006.
In 2009, the number of higher order multiple deliveries were 6,340, up slightly from 2008. The number of higher order multiple deliveries by type were:
- 5,905 triplets
- 355 quadruplets
- 80 quintuplets or higher
In 2008, the number of higher order multiple deliveries were 6,268, the lowest number in more than a decade. The number of higher order multiple deliveries by type were:
- 5,877 triplets
- 345 quadruplets
- 46 quintuplets or higher
In 2007, the number of higher order multiple deliveries were:
- 5,967 triplets
- 369 quadruplets
- 91 quintuplets
- 0 sextuplets or septuplets
Multiple Birth Risk Factors and Death Rates
The study indicated that multiples are at greater vulnerability for compromised outcome as compared with singletons. Multiples are more likely to be born early and smaller. The 2009 data clearly illustrates the risks of multiple birth. Nearly all higher order multiples (triplets, quadruplets, quintuplets or more) were born preterm (less than 37 weeks of gestation), and more than half of quadruplets and higher were considered very preterm at birth (less than 32 weeks). Consequently, higher order multiples also weighed less at birth. In 2009, 35 percent of triplet births were considered Very Low Birth Weight (VLBW), weighing less than 1,500 grams or three pounds, four ounces. By comparison, ten percent of twins and only one percent of singletons fell in this category. On average, twins weigh two pounds (960 grams) less than the average singleton at birth, and triplets weight about half of singletons at delivery. A shorter gestational age and smaller size makes multiples eight times as likely to die within the first month of life.
Data from 2005 found that twins are five times more likely than singletons to die within a month of birth while triplets were nearly 15 times more likely to die within a month of birth. (From 2005 data.)
Twinning Rates by Race
A slight increase was registered in twin birth rates rose among non-Hispanic white women (from 36.6 to 37.0 per 1,000) and non-Hispanic black women (from 36.8 to 38.0) between 2008 and 2009; the rate for Hispanic women was essentially unchanged at 22.5 (from 22.3). Since 1990, rates have risen 62 percent for non-Hispanic white women, 42 percent for non-Hispanic black, and 25 percent for Hispanic women.
For higher order multiples (triplets+), rates fluctuated slightly among non-Hispanic white women and Hispanic women, but the rate for non- Hispanic black births rose from 91.3 to 105.6. From 1990 through 1998, the triplet/+ rate for non-Hispanic whites rose nearly threefold, compared with increases of about 90 percent for non-Hispanic black and Hispanic births. Since 1998, the non-Hispanic white triplet/+ rate is down by more than 20 percent.
Among the three largest racial/origin groups in the United States, the twinning rates in 2009 are as follows:
- Non-Hispanic White: 37 per 1,000
- Non-Hispanic Black: 38 per 1,000
- Hispanic: 22.5 per 1,000
For triplets and other higher order multiples, the rates for 2009 are:
- Non-Hispanic White 201.4 per 100,000
- Non-Hispanic Black 105.6 per 100,000
- Hispanic 83.5 per 100,000
Maternal Age Factors
Older women are much more likely to give birth to twins or triplets. In 2009, 7% of all births to women 40 or older was a twin, compared with less than 2% of births to mothers under the age of twenty.
Twin Birth Rates, by Age of Mother: (per 1,000 births)
- All Ages 33.2
- Under 20 16.3
- 20-24 23.3
- 25-29 30.6,
- 30-34 41.4
- 35-39 49.9
- 40 and Over 71.0
Highest and Lowest Multiple Birth Rates By State
For the years 2007- 2009, the states with the highest twin birth rates were Connecticut, Massachusetts, and New Jersey. The state with the highest triplet+ birth rate was New Jersey, followed by Nebraska, and North Dakota. The lowest twin birth rate was reported in New Mexico. The state with the lowest triplet+ birth rate is Montana, followed by Maine and Alaska. (Results for Vermont were not reported.)
Sources: National Vital Statistics Reports, Vol 60. No. 1, November 2011 and Martin JA, Hamilton BE, Osterman MJK. Three decades of twin births in the United States, 1980–2009. NCHS data brief, no 80. Hyattsville, MD: National Center for Health Statistics. 2012.
|U.S. Multiple Birth Rates 1997 - 2009|
|Year||Twins||Triplets||Quadruplets||Quintuplets or More||Twin Birth Rate per 1,000 total births||Triplet Birth Rate (per 100,000 total births)||Quadruplet and Higher Birth Rate (per 100,000 total births)|