Note: In 2003 states started to implement the 2003 revision of the U.S. Standard Certificate of Live Birth. This significantly impacts the ability to compare temporal and regional prenatal care data. See detailed description below.
Timing of Prenatal Care
Timing of prenatal care calculations stratify the timing of the mother's entry into prenatal care into three categories. These categories include: "Early prenatal care," which is care started in the 1st trimester (1-3 months); "Second trimester care" (4-6 months); and "Late/no prenatal care," which is care started in the 3rd trimester (7-9 months) or no care received. Calculations are based on the number of live births to mothers in a specific prenatal care category divided by all live births excluding those missing data on prenatal care, multiplied by 100.
Adequacy of Prenatal Care
Adequacy of prenatal care calculations are based on the Adequacy of Prenatal Care Utilization Index (APNCU), which measures the utilization of prenatal care on two dimensions. The first dimension, adequacy of initiation of prenatal care, measures the timing of initiation using the month prenatal care began reported on the birth certificate. The second dimension, adequacy of received services, is measured by taking the ratio of the actual number of visits reported on the birth certificate to the expected number of visits. The expected number of visits is based on the American College of Obstetrics and Gynecology prenatal care visitations standards for uncomplicated pregnancies (1), and is adjusted for the gestational age at initiation of care and for the gestational age at delivery. The two dimensions are combined into a single summary index, and grouped into four categories: Adequate Plus, Adequate, Intermediate, and Inadequate. On the PeriStats web site, the percent of infants whose mothers received Adequate and Adequate Plus prenatal care are combined into one category, Adequate/Adeq+ prenatal care. Definitions for these categories include:
- Adequate Plus: Prenatal care begun by the 4th month of pregnancy and 110% or more of recommended visits received.
- Adequate: Prenatal care begun by the 4th month of pregnancy and 80-109% of recommended visits received.
- Intermediate: Prenatal care begun by the 4th month of pregnancy and 50-79% of recommended visits
- Inadequate: Prenatal care begun after the 4th month of pregnancy or less than 50% of recommended
- Adequate/Adeq+ used on the PeriStats web site can be defined as prenatal care begun by the 4th month of pregnancy and 80% or more of recommended visits received.
A more detailed description of APNCU can be found in (2).
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 multiple implications for tracking rates of prenatal care in the United States.(3) First, the timing of prenatal care item has changed. For data collected using the 1989 revision (all data prior to 2003), the item was recorded as the month of pregnancy that prenatal care began as reported by the mother. In 2003 the item was changed to request the date (day/month/year) of the first prenatal care visit, as recorded in the prenatal care or medical record. As a result of these modifications, rates of prenatal care timing and adequacy from the 2003 revision are not comparable to data collected using earlier birth certificate revisions.
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 timing and adequacy of prenatal care are not reported due to data incompatibilities between states. Comparison of prenatal care between states on different implementation schedules will not be possible. Furthermore, some states have implemented the 2003 revision mid-year, and in these cases data for that year are not shown. In 2006 California did not adopt the 2003 revision of prenatal care items. California fully implemented the 2003 revision in 2007. In 2007 not all births in Michigan are reported based on the 2003 revision, and data are not shown for that year. Finally, New York State implemented the 2003 revision in 2004 and New York City implemented in 2008. Rates of prenatal care for New York state exclude New York City from 2004 to 2007. Data for New York City can be found separately under city/county data.
On the PeriStats web site, graph bars displaying prenatal care data based on the 2003 revision are shown in red instead of the standard blue color. Tables indicate the change with an asterisk (*). At the U.S. level, separate timing of prenatal care rates for total revised and unrevised states are provided below the graph for the most recent year available. In addition, the functionality that allows you to make comparisons between regions has been removed from the prenatal care section of the web site. To date the following states on the PeriStats web site have implemented the 2003 revision:
- 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), IA, IN, 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)
This section of the web site will be updated as additional states implement the 2003 U.S. Standard Certificate of Live Birth.
- Standards for Obstetric-Gynecologic Services. 6th ed. Washington, DC: American College of Obstetricians and Gynecologists; 1985.
- Kotelchuck M. An evaluation of the Kessner Adequacy of Prenatal Care Index and a proposed Adequacy of Prenatal Care Utilization Index. Am J Public Health 1994; 84: 1414-1420.
- 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.