Describing the Increase in Preterm Births in the United States, 2014–2016

June 13, 2018

Questions for Joyce Martin, Statistician, and Lead Author of “Describing the Increase in Preterm Births in the United States, 2014–2016

Q: What did you think was the most interesting finding in your report?

JM: Two things – that the rate has increased for three straight years following several years of decline, and that the increase generally occurred among babies born late preterm.

Q: Why are total preterm birth rates increasing?

JM: The reasons for the rise are not well understood, but appear to be largely among births occurring at the highest end of the preterm/late range, that is, at 36 weeks.  That said, it is important to note that early preterm births, those at the greatest risk of poor outcome increased among non-Hispanic black births.

Q: Why did you decide to examine preterm birth rates?

JM: The preterm birth rate is a basic indicator of the maternal and infant health of a nation and, accordingly, changes in the preterm rate have important implications for the public health. Babies born prior to 37 weeks of gestation are more likely to die within the first year of life and more likely to suffer life-long morbidities than those born later in pregnancy.

Q: How did preterm birth rates vary among U.S. states from 2014-2016?

JM: Preterm rates rose significantly in 23 states and the District of Columbia and non-significant increased were seen in an additional 22 states.  In short, rates are trending upward for the vast majority of states.

Q: What is the take home message in this report?

JM: The incidence of infants born too soon is on the rise in the US, appears to be largely among late preterm births and the rise does not appear to be limited to any specific maternal race, age or geographic group.


Births: Provisional Data for 2017

May 17, 2018

Questions for Brady E. Hamilton, Ph.D., Demographer, Statistician, and Lead Author of “Births: Provisional Data for 2017

Q: What did you think was the most interesting finding in your new analysis?

BH: The report includes a number of very interesting findings. The general fertility rate, 60.2 births per 1,000 women aged 15–44, declining 3% in 2017 and reaching a record low is certainly noteworthy. In addition, the continued decline in the birth rate for teens, down 7% from 2016 to in 2017, and reaching another record low, is very significant. The increase in the cesarean delivery rate following several years of decline is noteworthy as are the recent increase in rates of preterm and low birthweight births.

Q: Why does fertility keep going down in the U.S.?

BH: In general, there are a number of factors associated with fertility. The data on which the report is based comes from the birth certificates registered for births in the U.S. While the scope of this data is essentially all births in the country, and provides detailed information about rare events, small areas, or small population groups, the data does not provide information about the parent’s decision to have (or not have) a child. And so, accordingly, we cannot examine the “why” of the changes and trends in births.

Q: Does the decline in the Total Fertility Rate essentially mean fertility is down below “replacement” levels?  Could you explain this in general terms?

BH: “Replacement” refers to a minimum rate of reproduction necessary for generation to exactly replace itself, that is, enough children born to replace a group of 1,000 women and their partners. For the total fertility rate, this rate is generally considered to be 2,100 births per 1,000 women. In 2017, the total fertility rate, 1,764.5 births per 1,000 women, was below replacement.

Q: Do the increases among women over 40 suggest a “new norm” in people waiting till much later to have children?

BH: Birth rates for women aged 40-44 and 45-49 years have increased generally over the last 3 decades. Given this, it reasonable to expect this trend to continue.

Q: Are the annual declines in teen pregnancy something that we are in danger of taking for granted?

BH: The birth rate for females aged 15-19 has decreased 8% per year from 2007 through 2017. For comparison, the decline in the birth rates for women aged 20-24 and 25-29 was 4% and 2% from 2007 through 2017. The decline in teen births is very noteworthy.

Q: Can you explain how the increases in preterm births and low birthweight are connected?

BH: Infants born preterm are also often, but not exclusively, born low birthweight and vice-versa.  The causes of the recent upward shift in these rates are not well understood.

Births: Final Data for 2015

January 5, 2017

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.

Cesarean delivery – more popular than ever before

March 24, 2010

A report released yesterday from the National Center for Health Statistics showed that the cesarean rate rose by 53% from 1996 to 2007, reaching 32%, the highest rate ever reported in the United States. The 1.4 million cesarean births in 2007 represented about one-third of all births in the United States.

Although clear clinical indications often exist for a cesarean delivery, the short- and long-term benefits and risks for both mother and infant have been the subject of intense debate for over 25 years. Despite this, the rate continues to rise for women in all racial and ethnic groups, as well as for women of every age, as shown below.

Rates of cesarean delivery typically rise with increasing maternal age. As in 1996 and 2000, the rate for mothers aged 40–54 years in 2007 was more than twice the rate for mothers under age 20 (48% and 23%, respectively).For more from this recent release, visit

Have late preterm births increased among mothers of all ages?

November 18, 2009

Late preterm birth rates have risen among mothers of all ages from 1990 to 2006, including teenage mothers (up 5 percent). Among mothers age 25 years and over, late preterm birth rates increased by more than 20 percent from 1990 to 2006. Younger (under age 20 years) and older (40 years and over) mothers are the most likely to have a late preterm baby.

For more trends in late preterm births in the United States, visit the NCHS Data Brief at