Pushing for 39 weeks: Are pregnancies getting longer?

Pushing for 39 weeks: Are pregnancies getting longer?Michelle J.K. Osterman, M.H.S.Joyce A. Martin, M.P.H.

National Center for Health Statistics

Extending Our Reach Through PartnershipsJune 2-6, 2013 Phoenix, Arizona1Why?Better outcomes with longer gestation 39 or more weeksUnder 39 weeksEarly termLate preterm38 weeks37 weeks36 weeks35 weeks34 weeksWhy do we care about the length of pregnancy?

Because in healthy pregnancies there are better outcomes for mothers and children for births that occur at 39 or more weeks than births before 39 weeks. The green symbol here means better than.

Even under 39 weeks, there are better outcomes for each additional week of gestation in a healthy pregnancy, so early term is generally better than late preterm,

and within those groups, 38 is better than 37 weeks, and so on.2OutlineOutcomes by gestational ageLate preterm (34-36 weeks)36 weeksEarly term births (37-38 weeks)

Labor and Delivery Management by gestational ageInduction of LaborCesarean delivery

To explore this question well be looking at outcomes by gestational age, focusing on the percentage late preterm and early term births over the past several years, as well as induction of labor and cesarean delivery by gestational age.3MethodsBirth certificate data1990-2010 final2011 preliminary

Focus on births under 39 weeksGestational age based on date of last menstrual periodSingletons only

Well be using national birth certificate data from the 1990 through 2010 final natality files as well as 2011 preliminary data.

Well be focusing on births under 39 weeks. Gestational age is based primarily on the date of the last menstrual period, and data are limited to singleton births only, since plurality is highly influential in labor and delivery management.4MethodsIncludes all birthsMedically-indicated Nonmedically-indicated

DefinitionsInduction of labor = artificial initiation of labor prior to the onset of spontaneous laborCesarean delivery = surgical extraction of the fetus, placenta, and membranes through abdominal incision

Also, while the previous presenters have talked about reducing nonmedically-indicated procedures prior to 39 weeks, this analysis includes all births and does not make a distinction based on medical indication because of current data quality limitations.

Just for quick reference, induction of labor is artificial initiation of labor prior to the spontaneous onset, and cesarean delivery is surgical extraction of the fetus through an incision in the abdomen.

5Gestational ageFirst, lets look at trends in gestational age over the last 2 decades.6Births by gestational age: United States, 1990-2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System39 or more weeksUnder 39 weeks(slides 7-8)

This figure shows trends in births by a very simple breakdown of gestational age for births occurring before 39 weeks and births at 39 or more weeks from 1990 to 2011. You can see that, as births at 39 or more weeks declined from 1990 to 2006, births under 39 weeks increased.

The percentage of births before 39 weeks rose from 29.1 percent in 1990 to the peak of 40.0 percent in 2006, a 37 percent increase.

The percentage of births under 39 weeks has since decreased 11 percent to 35.7 in 2011.

7Births by gestational age: United States, 1990-2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System39 or more weeksUnder 39 weeks37%-11%(slides 7-8)

This figure shows trends in births by a very simple breakdown of gestational age for births occurring before 39 weeks and births at 39 or more weeks from 1990 to 2011. You can see that, as births at 39 or more weeks declined from 1990 to 2006, births under 39 weeks increased.

The percentage of births before 39 weeks rose from 29.1 percent in 1990 to the peak of 40.0 percent in 2006,

a 37 percent increase.

The percentage of births under 39 weeks has since decreased 11 percent to 35.7 in 2011.8Gestational age groupsUnder 39 weeksLess than 34 weeks = Early preterm34-36 weeks = Late preterm37-38 weeks = Early term

39 or more weeks

The next few slides examine more closely where the changes in births under 39 weeks have occurred. Less than 34 weeks of gestation is considered early preterm, 34 to 36 weeks is late preterm and 37 to 38 weeks is now considered early term. Births at 39 or more weeks also break down into more specific groups, but they are not the focus of this presentation.9Births by gestational age: United States, 1990 and 2006NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System19902006(slides 10-11)

This figure shows the percentages of births occurring at early preterm, late preterm, and early term for 1990 and 2006. The percentage early preterm births rose very slightly to 3 percent. The percentage of late preterm births increased 19 percent during this time. And, you can see the largest change was for early term births, which increased 49 percent.

10Births by gestational age: United States, 1990, 2006 and 2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System199020062011(slides 10-11)

This figure shows the percentages of births occurring at early preterm, late preterm, and early term for 1990 and 2006. The percentage early preterm births rose very slightly to 3 percent. The percentage of late preterm births increased 19 percent during this time. And, you can see the largest change was for early term births, which increased 49 percent.

Looking at changes from 2006 to 2011, you see declines for all gestational age categories under 39 weeks. The percentage of early preterm births declined to 2.8 percent in 2011. Late preterm births decreased 10 percent to 7.3 percent of births. Again, the largest change was for early term births, which decreased 11 percent.

11Births by gestational age: United States, 2006 and 2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemEarly termLate preterm(slides 12-15)

To dig a little deeper into the decline at late preterm and early term, which account for most of the changes under 39 weeks from 2006 to 2011, this figure focuses on the changes for individual weeks 34-38. The declines for 34 and 35 weeks were statistically significant, but small, at 1 and 2 tenths of a point, respectively. Births occurring during each of these two weeks have fluctuated by approximately this much every year since 1990.

12Births by gestational age: United States, 2006 and 2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemEarly termLate preterm(slides 12-15)

The percentage of births at 36 weeks, which account for more than half of late preterm births, decreased 11 percent.

13Births by gestational age: United States, 2006 and 2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemEarly termLate preterm(slides 12-15)

Births at 37 weeks decreased 9 percent.

14Births by gestational age: United States, 2006 and 2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemEarly termLate preterm(slides 12-15)

To dig a little deeper into the decline at late preterm and early term, which account for most of the changes under 39 weeks from 2006 to 2011, this figure focuses on the changes for individual weeks 34-38. The declines for 34 and 35 weeks were statistically significant, but small, at 1 and 2 tenths of a point, respectively. Births occurring during each of these two weeks have fluctuated by approximately this much every year since 1990.

The percentage of births at 36 weeks, which account for more than half of late preterm births, decreased 11 percent.

Births at 37 weeks decreased 9 percent.

But the largest decline was for early term births at 38 weeks, which decreased 12 percent. Births at 38 weeks account for a larger percentage of births than the other 4 weeks combined.

15Births under 39 weeks2006-2011 decrease36 weeks (late preterm)37 weeks (early term)38 weeks (early term)

Combine weeks 36-38Its clear that most of the decrease from 2006 to 2011 occurred at weeks 36, 37, and 38. Therefore, although its unconventional, weve combined the late preterm week 36 with the early term weeks 37 and 38 for further analysis.

This figure shows that, in 2006, 33.3 percent of births were born at 36 to 38 weeks, compared with 29.6 percent in 2011.

16Change in percentage of births occurring at 36-38 weeks: 2006 and 2011MTWYIDWAORUTCANDSDNECOTXOKKSARMOMNILKYTNALGAFLSCVAWVOHDECTMANJDEDCDecreaseNOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemAKHIAZLAINMINYNCNENMIAWIPAMERINHVTMD(slides 17-18)

Looking at change in births at 36-38 weeks by state illustrates how widespread this change in trends is; 49 states and DC reported significant declines in births at 36-38 weeks. 17Change in percentage of births occurring at 36-38 weeks: 2006 and 2011DecreaseMSNo changeNOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System(slides 17-18)

Looking at change in births at 36-38 weeks by state illustrates how widespread this change in trends is; 49 states and DC reported significant declines in births at 36-38 weeks.

The percentage for the remaining state was steady during this time.18Induction of LaborNow well look at whats happening with induction of labor.19Induction of labor: United States, 1990-2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemAll gestational agesThis figure shows the trend in induction of labor from 1990-2011. In 1990, 9.6 percent of births were reported to have been induced. By 2010, this percentage increased to 23.8, an increase of 147 percent. Between 2010 and 2011, the induction rate decreased by 1 tenth of a percent to 23.7 percent. This is the first decrease in inductions since these data started being collected in 1989.20Induction of labor by gestational age: United States, 1990-2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemUnder 39 weeks39 or more weeks(slides 21-22)

However, trends in induction of labor over this period vary by gestational age as shown in this figure. As you can see, induction rates at 39 or more weeks follows the overall pattern, increasing until 2010 and then decreasing slightly in 2011.

21Induction of labor by gestational age: United States, 1990-2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemUnder 39 weeks39 or more weeks-7%(slides 21-22)

However, trends in induction of labor over this period vary by gestational age as shown in this figure. As you can see, induction rates at 39 or more weeks follows the overall pattern, increasing until 2010 and then decreasing slightly in 2011.

In contrast, the induction rate for births under 39 weeks peaked in 2005 and 2006 and then started to decline.

The 2011 induction rate is 7 percent lower than that of 2006.

22Induction of labor by gestational age: United States, 1990 and 2006NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System19902006(slides 23-24)

This figure shows the gestational age detail that we explored in the first part of this presentation, first showing induction rates for 1990 and 2006 for individual late preterm and early term weeks. As you see, induction rates more than doubled for each week from 1990-2006. 23Induction of labor by gestational age: United States, 1990, 2006 and 2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System199020062011(slides 23-24)

This figure shows the gestational age detail that we explored in the first part of this presentation, first showing induction rates for 1990 and 2006 for individual late preterm and early term weeks. As you see, induction rates more than doubled for each week from 1990-2006.

However, changes from 06 to 11 varied by gestational age.

Induction rates at 34 and 35 weeks were essentially unchanged during this time. The differences shown here were not statistically significant.

In contrast, induction rates at 36, 37, and 38 weeks decreased during this time.

The largest decrease occurred at 38 weeks, which went down 11 percent.24Births under 39 weeks2006-2011 decrease36 weeks (late preterm)37 weeks (early term)38 weeks (early term)

Combine weeks 36-38Again, changes at weeks 36, 37 and 38 are driving the overall trend, so weve grouped these weeks for further analysis.

This figure shows the rate of induction for 36 to 38 weeks decreased 9 percent from 2006 to 2011.

25Change in induction of labor at 36-38 weeks: 2006 and 2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System(slides 26-29)

Now by state26Change in induction of labor at 36-38 weeks: 2006 and 2011MTWYIDWAORUTCANDSDNECOTXOKKSARMOMNILKYTNALGAFLSCVAWVOHDECTMANJDEDCDecreaseNOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System(slides 26-29)

Declines in induction rates for 36-38 weeks from 06 to 11 were widespread, occurring in 32 states and DC. Decreases by state ranged from 4 to 37 percent, with 10 states having induction rates that were at least 20 percent lower in 2011 than in 2006.27Change in induction of labor at 36-38 weeks: 2006 and 2011DecreaseNENMMSIAWIPAMENo changeRINHVTMDNOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System(slides 26-29)

An additional 10 states had steady rates during this time,28Change in induction of labor at 36-38 weeks: 2006 and 2011AKHIAZLAINMINYNCDecreaseNo changeIncreaseNOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System(slides 26-29)

Now by state

Declines in induction rates for 36-38 weeks from 06 to 11 were widespread, occurring in 32 states and DC. Decreases by state ranged from 4 to 37 percent, with 10 states having induction rates that were at least 20 percent lower in 2011 than in 2006.

An additional 10 states had steady rates during this time,

and the remaining 8 states had higher rates of induction in 2011 than in 2006. 29Cesarean deliveryNow, moving on to cesarean delivery, weve got a slightly different story to share.30Cesarean delivery:United States, 1990-2011NOTES: Singletons only. 2011 data are preliminary. Source: CDC/NCHS, National Vital Statistics SystemAll gestational agesThis figure shows the singleton cesarean delivery rate from 1990-2011. In contrast to induction of labor, the cesarean delivery rate reached its lowest point in 1996-97 and increased until peaking in 2009. 2010 saw no change in the rate, which then declined to 31.2 percent in 2011.31Cesarean delivery by gestational age:United States, 1990-2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System39 or more weeksUnder 39 weeks(slides 32-33)

Trends are different by gestational age, however. Cesarean deliveries at 39 or more weeks were at their lowest point in 1997 and has increased every year since then.32Cesarean delivery by gestational age:United States, 1990-2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System39 or more weeksUnder 39 weeks-2%(slides 32-33)

Trends are different by gestational age, however. Cesarean deliveries at 39 or more weeks were at the lowest point in 1997 and have increased every year since then.

Among births under 39 weeks, the cesarean delivery rate peaked in 2009, but has declined more than 2 percent from 2009-11.

33Cesarean delivery by gestational age: United States, 1996 and 2009NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System19962009(slides 34-35)

Again, showing the gestational age detail, this figure shows cesarean delivery rates for 1996 and 2009 for individual late preterm and early term weeks. And its clear that cesarean delivery rates increased considerably for each week during this time.34Cesarean delivery by gestational age: United States, 1996, 2009 and 2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System199620092011(slides 34-35)

Again, showing the gestational age detail, this figure shows cesarean delivery rates for 1996 and 2009 for individual late preterm and early term weeks. And its clear that cesarean delivery rates increased considerably for each week during this time.

From 2009 to 2011, changes for 34, 35 and 36 weeks were not significant.

The cesarean delivery rate for births at 37 weeks was down slightly during this time. At 38 weeks, the cesarean rate decreased 6 percent. This is actually a continued decrease for cesarean deliveries at 38 weeks from 2007.

35Change in cesarean delivery at 37 weeks: 2006 and 2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System(slides 36-39)

The change in cesarean delivery trends is different than the other trends shown, that is, the next series of slides show state-specific changes for early term weeks 37 and 38 separately, rather than the combined weeks 36 to 38.

Cont.36Change in cesarean delivery at 37 weeks: 2006 and 2011DecreaseNOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemDECOTXMA(slides 36-39)

At 37 weeks, while the national rate decreased, rates for only 4 states followed suit.

Cont.37Change in cesarean delivery at 37 weeks: 2006 and 2011DecreaseNOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemNo changeMTWYIDWAORUTCANDSDNEOKKSARMOMNILKYTNALGAFLSCVAOHDECTNJRIAKAZNENMNHVTMEPANYMIINIAWINCLAMS(slides 36-39)

Rates for 44 states were unchanged between 2009 and 2011.

Cont.38Change in cesarean delivery at 37 weeks: 2006 and 2011DecreaseNOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemNo changeIncreaseHIWVDCMD(slides 36-39)

The change in cesarean delivery trends is different than the other trends shown, therefore, the next series of slides show state-specific changes for early term weeks 37 and 38 separately, rather than the combined weeks 36 to 38.

At 37 weeks, while the national rate decreased, rates for only 4 states followed suit.

Rates for 44 states were unchanged between 2009 and 2011. And rates for West Virginia, Maryland, and DC were higher in 2011 than in 2009.39Change in cesarean delivery at 38 weeks: 2006 and 2011NOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics System(slides 40-42)

At 38 weeks,

Cont.40Change in cesarean delivery at 38 weeks: 2006 and 2011DecreaseNOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemWAORUTCANEOKMOMNILGAFLSCOHDECTNJMAAKAZNENHPANYMIINNCCOTXDEHI(slides 40-42)

cesarean delivery rates decreased in 29 states from 2009 to 2011.

Cont. 41Change in cesarean delivery at 38 weeks: 2006 and 2011DecreaseNOTES: Singletons only. Source: CDC/NCHS, National Vital Statistics SystemMTWYIDNDSDKSARKYTNALVADENMVTMEIAWILAMSRIWVDCMDNo change(slides 40-42)

At 38 weeks,

cesarean delivery rates decreased in 29 states from 2009 to 2011.

Rates in 21 states and DC were unchanged and there were no increases in state-specific cesarean delivery rates from 2009 to 2011.42Summary43SummaryOverall ratesInduction of labor increased from 1990-2006Cesarean delivery increased from 1996-2009

Among births under 39 weeks1990-2006Percentage of births increasedMost of increase occurred at late preterm and early termRate of induction of labor increasedMost of increase occurred at 36-38 weeks1996-2009Rate of cesarean delivery increasedMost of increase occurred at 37-38 weeksNow to summarize

The overall rate of induction of labor increased from 1990 to 2006 and the cesarean delivery rate increased from 1996-2009.

Among births under 39 weeks, the percentage of births increased from 1990-2006, most of this change occurred among late preterm and early term births. Also, the induction rate for births under 39 weeks increased substantially during this time. Most of the increase in induction rates occurred at 36-38 weeks. Cesarean delivery showed similar trends, increasing between 1996 and 2009. Most of this change occurred at early term weeks 37 and 38.44SummaryAmong births under 39 weeks2006-2011Percentage of births declined 11%Most of decline occurred at 36, 37, and 38 weeksPercent of 36-38-week births was down in 49 states and DC

Induction of labor rate declined 7%All of decline at 36-38 weeksRates at 36-38 weeks declined in 32 states and DC; increased in 8 states

From 2006 to 2011, the percentage of births under 39 weeks declined 11 percent. Most of this decline occurred at 36-38 weeks and the percentage of 36-38-week births decreased in 49 states and DC during this time.

The rate of labor induction declined 7 percent from 2006 to 2011, again, mostly at 36-38 weeks. 32 states and DC had lower induction rates for 36-38-weeks births in 2011 than in 2006. 8 states had higher rates.45SummaryAmong births under 39 weeks2009-2011Rate of cesarean delivery declined 2%Decline mainly occurred at 37 and 38 weeksRates at 37 weeks declined in 4 states; increased in 2 states and DC Rates at 38 weeks declined in 29 states; unchanged in 21 states and DC

The cesarean delivery rate started to decline later than induction, but was 2 percent lower in 2011 than in 2009. Most of this decline occurred at 37 and 38 weeks of gestation. State-specific rates of cesarean delivery declined in 4 states and increased in 2 states and DC from 2009 to 2011. All other state rates were unchanged. At 38 weeks, state-specific rates declined in 29 states and were unchanged in the remaining 21 states and DC during this time.46LimitationsInduction of laborGestational age

No distinction for medical indicationMedical items not comprehensiveCurrent data quality concernsE.g., fetal intolerance of labor

Before I finish, theres just a few limits to mention about data quality.

First, these items have varying quality. According to recent validity studies, induction of labor is currently underreported on the birth certificate. Method of delivery, however, is well reported.

The quality of gestational age based on LMP can be problematic, and, as you may know if you attended yesterdays round table discussion or saw the poster, were changing to the obstetric estimate-based gestational age measurement.

Finally, these data do not distinguish between medically-indicated and non-medically indicated induction of labor and cesarean delivery because, 1) the birth certificate can only approximate a medically-indicated birth because it does not include a comprehensive list of medical items, and 2) some of the necessary items that are included on the birth certificate, such as fetal intolerance of labor, are not well reported. Hopefully, with efforts such as the ones described here today, these data can improve and become reliable in determining what is or isnt medically-indicated.

47ConclusionsInduction of labor and cesarean delivery are declining for births under 39 weeks.

Percentage of births under 39 weeks declining

Decline in births under 39 weeks is more wide-spread than declines in induction of labor and cesarean delivery

Pregnancies are getting longer!

And finally, the take-home messages here are that induction of labor and cesarean delivery are declining for births under 39 weeks.

The percentage of births under 39 weeks is also declining.

The decline in births under 39 weeks, however, is more wide-spread than the decline in induction of labor and cesarean delivery, and more research is required on risk factors, prenatal care, and so forth, in order to tease out what else is influencing these trends.

But, after all that, its clear that as a whole, we are pushing for 39 weeks and that pregnancies do indeed appear to be getting longer and hopefully, with that, well have healthier babies.

48

Thank you!49