Questions for Joyce Martin, Lead Author of, “Is Twin Childbearing on the Decline? Twin births in the United States, 2014-2018.”
Q: Is this the first time you have published a report on this topic?
JM: General information on twin births is published annually in the National Vital Statistics Report series “Births: Final Data.” A number of special reports have also been published on the topic in the past.
Q: Why did you decide to do a report on trends in twin births?
JM: There appears to be a reversal in the direction of trends in twin childbearing in the US. After increasing for decades, the number and rate of twin births trended downward for 2014-2018. This is important to public health because of the greater risk of poor pregnancy outcome, such as preterm birth and infant death, for babies born in twin pregnancies compared with those born in single pregnancies.
Q: How did the data vary by maternal age, race and Hispanic origin and state of residence?
JM: Trends differed by all of these characteristics. Rates for women in their 30s and over declined by 10%-12% and rates for women 40 and over by more than 20%. In contrast, there was no significant change in trends for women in their twenties. Among the three race/Hispanic origin groups studied, twin childbearing declined for 2014-2018 among non-Hispanic white women but were essentially unchanged among non-Hispanic black and Hispanic women. Rates declined significantly in 17 states and increased in only three states.
Q: Was there a specific finding in your report that surprised you?
JM: The steady decline in twinning from 2014 through 2018 after many years of increases was surprising as was the fairly large declines among women aged 30 and over.
Q: Do you foresee the decline in twins continuing?
JM: As fertility procedures continue to improve, twin births, and especially higher-order multiple births, would be expected to continue to decline. However, it is important to note that older mothers, those aged 35 and over, are more likely to have a twin delivery without the use of fertility therapies. The older age of women at birth may also affect twining rates.
Questions for Joyce A. Martin, M.P.H., Demographer, Statistician, and Lead Author on “Births: Final Data for 2015”
Q: Was there a result in your study’s analysis of births in the United States that you hadn’t expected and that really surprised you?
JM: Although small, (from 9.57% to 9.63%) the rise in the preterm birth rate (births of less than 37 completed weeks of gestation) was unexpected. This rate had been declining steadily since 2007.
Also of note is the decline in the triplet and higher-order multiple birth rate, down 9% from 2014 to 2015, and a decrease of 46% since 1998. The year 2015 also is the third straight year of declines in the rate of cesarean delivery (rate of 32.0% in 2015).
The continued, large decline in the teen birth rate (down 8% from 2014 to 2015) was also somewhat surprising, although not unprecedented. From 2007 through 2014, the teen birth rates had declined 7% annually.
Q: What is the difference between this new births report and the other reports your office produced on 2015 birth data, like the preliminary data report on 2015 births and the Data Brief on teen births?
JM: The annual report “Births: Final Data for 2015” offers substantially more detail (e.g., age, race and Hispanic origin of mother, state) on key topics, than does the report on preliminary birth statistics (“Births: Preliminary Data for 2015”). The final report also includes information on topics not included in the preliminary reports such as multiple births, attendant and place of birth, birth order and birth rates for fathers.
Q: How has the number of births in the United States changed in 2015 from previous years?
JM: The number of births in the United States declined slightly in 2015 (by 9,579 births to 3,978,497) from 2014. The decline for 2015 followed an increase in births for 2014, which was the first increase since 2007.
Q: What differences, if any, did you see among race and ethnic groups, and among various ages?
JM: Of continued concern are the higher risks of poor birth outcomes as measured by levels of preterm birth and low birthweight among non-Hispanic black mothers compared with total births and other race and Hispanic origin groups. For example, in 2015 the preterm birth rate for births to non-Hispanic black mothers was more than 50% higher at 13.41% than for non-Hispanic white women (8.88%) and nearly 50% higher than the rate for births to Hispanic mothers (9.14%).
Q: Did you observe any regional or state differences in this study on births?
JM: Differences by state were observed for many of the demographic and medical/health items included in the 2015 final birth report. For example, from 2014 to 2015, the general fertility rate–which is the number of births per 1,000 women aged 15–44–declined in eight states and was essentially unchanged in the 42 states and the District of Columbia (DC). In 2015, the general fertility rate ranged among states from 51.1 births per 1,000 women aged 15–44 in Vermont to 78.2 in South Dakota.
Also, increases in preterm birth rates were limited to four states from 2014 to 2015: Arkansas, California, Nebraska, and North Carolina. Rates declined in four states: Montana, New York, Texas and Wyoming. Nonsignificant differences were reported for the remaining states and DC.
The incidence of triplet and higher-order multiple births rose fourfold during the 1980s and 1990s. This rise was associated with older maternal age and the increased use of fertility-enhancing therapies and was of concern because of the greater risk of adverse outcome of triplet and higher-order births compared with singletons and the added toll of these pregnancies on maternal health.
Since 1998, however, this trend has edged downward.
An NCHS report explores the recent downturn in triplet and higher-order births by maternal demographic factors.
- The triplet and higher-order birth rate declined 41% from 1998 to 2014, or from about 1 in every 515 births in 1998 to one in every 880 births in 2014.
- Triplet and higher-order birth rates were down by about 50% or more for women aged 25 and over. Rates were essentially unchanged for women under 25.
- The largest declines in triplet and higher-order birth rates by race and Hispanic origin for 1998–2014 were for non-Hispanic white women, down 46% compared with a 15% decline for Hispanic women, and essentially no change for non-Hispanic black women.
- Triplet and higher-order birth rates were down from 1998–2000 to 2012–2014 in 42 states; declines of more than 50% were observed in 7 states.
NCHS birth tables with a variety of variables for selection are available at http://www.cdc.gov/nchs/datawh/vitalstats/VitalStatsbirths.htm.
By selecting the national or subnational (i.e., state and some county) levels, you can find specific statistics for national, state, and some county birth rates, fertility rates, method of delivery (vaginal or cesarean), length of pregnancy, birthweight, characteristics of the mother (i.e., age, race, marital status, education), prenatal care, and risk factors (i.e., diabetes, hypertension, and smoking). For journalists who need assistance, feel free to contact the NCHS press office.
The teen birth rate increased in more than half of all 50 states in 2006, according to an NCHS report released today. Click here for the report.
The data show teen birth rates were highest in the South and Southwest, with the highest rate recorded in Mississippi (68.4), followed by New Mexico (64.1) and Texas (63.1).
Teen birth rates in 2006 were lowest in the Northeast in 2006, with the lowest rates occurring in New Hampshire (18.7), Vermont (20.8), and Massachusetts (21.3). The only states with a decrease in teen birth rates between 2005 and 2006 were North Dakota, Rhode Island, and New York.
NCHS reported in December 2007 that the teen birth rate for the nation as a whole increased for the first time in 15 years in 2006 from 40.5 births per 1,000 women aged 15-19 in 2005 to 41.9 in 2006.
The report also features birth data on a variety of topics, including state-based and national information on teen, unmarried, and multiple births, along with health data on smoking during pregnancy, cesarean delivery, preterm birth, and low birthweight.
The twin birth rate rose 2 percent for 2004, to 32.2 twins per 1,000 total births, another record high. The twinning rate has climbed 42 percent since 1990 (from 22.6), and 70 percent since 1980 (18.9). The number of live births in twin deliveries rose to 132,219, nearly double the number reported for 1980 (from 68,339).
In contrast to the continued upswing in twin births, the rate of triplet and higher-order multiple births (triplet/+ birth rate) declined 6 percent for 2004, to 176.9 per 100,000, from 187.4 in 2003. The triplet/+ birth rate (the number of triplets, quadruplets, quintuplets, and other higher-order multiples per 100,000 live births) soared by more than 400 percent between 1980 and 1998 (from 37.0 to 193.5 per 100,000 births) (125). Since 1999, however, this rate has been comparatively stable, trending slightly downward; the current year level is 9 percent lower than the 1998 peak. In 2004, 7,275 triplets/+ were born, a drop of 5 percent from the previous year, and the lowest number reported since 1997. Similar trends in twinning and in triplet/+ birth rates have been observed over the last several decades in England and Wales.
One of our most frequently asked questions is about multiple births. For your convenience multiple births since 1971 are available here.