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Maternal & Infant Health Research Registries

During the pandemic, tracking health outcomes is essential to improving care, developing policies and understanding the impact of this pandemic on maternal and infant health. Learn more about global research and registries that are tracking the data to ensure the health of mothers and babies.

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COVID-19 Resources & Literature

A resource compiling up-to-date published literature on COVID-19 relating to mothers and babies. We have gathered scientifically sound research to help guide further studies or keep you up to date with the maternal child health population and COVID-19.

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Delivery Method

Note: In 2003 states started to implement the 2003 revision of the U.S. Standard Certificate of Live Birth and by 2016 all states had completed implementation. Some method of delivery data is not comparable across revisions. In June 2018, select delivery method indicators based on the 1989 revision of the birth certificate are no longer available on PeriStats. A limited number of delivery method indicators and years are available on PeriStats for states that implemented the 2003 revision most recently. See detailed description below.


Delivery Method rates are calculated for total Cesarean births, primary Cesarean births, vaginal births after Cesarean births (VBAC), and repeat Cesarean births.

The total Cesarean birth rate is calculated as the number of births delivered by cesarean section divided by the total number of live births less the not-stated values for delivery method, multiplied by 100.

The primary Cesarean birth rate is calculated as the number of women having a first Cesarean delivery divided by the number of live births to women who have never had a Cesarean delivery, multiplied by 100. The denominator for this rate excludes those with method of delivery classified as repeat cesarean, vaginal birth after previous cesarean, or method not stated.

The VBAC rate is calculated as the number of VBAC deliveries resulting in a live birth divided by the sum of VBAC and repeat cesarean deliveries, multiplied by 100.

The repeat Cesarean birth rate is calculated as the number of repeat cesarean deliveries resulting in a live birth divided by the sum of VBAC and repeat cesarean deliveries, multiplied by 100.

Impact of Birth Certificate Revision

The transition from the 1989 revision of the U.S. Standard Certificate of Live Birth to the 2003 revision has some implications on tracking rates of primary and repeat Cesarean births and VBAC deliveries in the United States.(1) The method of delivery item on the 2003 revision specifically asks if the mother had a previous cesarean section delivery under the "Risk Factors for Pregnancy" section of the birth certificate. In past revisions this information was indicated by a checkbox for VBAC under the method of delivery section. As a result of this modification, rates of VBAC and primary Cesarean delivery from the 2003 revision are not comparable to data collected using earlier birth certificate revisions. Specifically, under the 2003 revision, rates of VBAC deliveries and primary cesarean section deliveries are slightly higher than expected, and repeat cesarean section deliveries are slightly lower. Total cesarean section and vaginal delivery rates are not impacted.

The state implementation of the 2003 revision also impacts U.S. and state temporal trends. While some states began using the revised birth certificate in 2003, the schedule for implementation varies by state. Therefore, starting in 2003, total U.S. rates of VBAC and primary cesarean deliveries are not reported due to data incompatibilities between states. Furthermore, some states have implemented the 2003 revision mid-year, and in these cases data for that year are not shown. In 2007 not all births in Michigan are reported based on the 2003 revision, and data are not shown for that year. Additionally, New York state started using the 2003 revised birth certificate in 2004 and New York City implemented in 2008. New York state VBAC and primary Cesarean delivery rates exclude New York City from 2004 to 2007. Data for New York City can be found separately under city/county data. New Jersey's implementation spanned two years, 2014-2015, and therefore data on primary, repeat, and VBAC deliveries will be available on PeriStats beginning with 2016 data.

Beginning in June 2018, data on delivery method based on the 1989 revision of the birth certificate is no longer displayed on PeriStats. All states implemented the 2003 birth certificate by 2016. Data on primary cesarean, repeat cesarean and VBAC for the U.S., HHS, and the last states to implement the new birth certificate (CT and NJ) will not be available until 2016. In addition, the functionality that allows you to make comparisons between regions will show only the years for which both areas have data available. States implemented the 2003 revision of the birth certificate in the following years:

  • 2003: PA, WA
  • 2004: FL (mid-year), ID, KY, NH (mid-year), NY (excluding New York City), SC, TN
  • 2005: KS, NE, PR, TX, VT (mid-year)
  • 2006: CA (partially), DE, ND, OH, SD, WY
  • 2007: CO, GA (mid-year), IN, IA, MI (partially)
  • 2008: MT, NM, New York City, OR
  • 2009: DC (mid-year), NV (mid-year), OK (mid-year), PR, UT
  • 2010: IL, LA (mid-year), MD, MO, NC (mid-year)
  • 2011: MA (mid-year), MN (mid-year), WI
  • 2012: VA (mid-year)
  • 2013: AK, ME (mid-year), MS
  • 2014: AL, AZ, AR, HI, NJ (mid-year), WV
  • 2015: NJ (mid-year)
  • 2016: CT

  1. Martin JA, Hamilton BE, Sutton PD, et al. Births: Final data for 2003. National vital statistics reports; vol 54 no 2. Hyattsville, MD: National Center for Health Statistics. 2005.