About the Reproductive & Birth Outcomes Data

This page provides general information about the reproductive and birth outcomes data and measures developed by the Minnesota Environmental Public Health Tracking Program. For more information about these data, contact Minnesota Public Health Data Access.

Information on this page:

What these data tell us:

  • The numbers and rates of prematurity, low birth weight, infant mortality, and sex ratio in Minnesota by year and race/ethnicity.
  • If certain reproductive and birth outcomes or sex ratio are going up or down over time.
  • If a segment of a population is at increased risk for adverse reproductive or birth outcomes.

How we can use these data:

  • To inform the public about adverse reproductive and birth outcomes.
  • For program planning and evaluation by state and local partners.

What these data do not tell us:

  • The causes of reproductive and birth outcomes
  • Environmental exposure-related causes of adverse reproductive and birth outcomes are only one piece of a puzzle that includes many other factors such as access to and quality of health care, maternal characteristics, genetic factors, behavioral factors, childcare skills, and injury prevention. Many of these factors are not included in birth or death records. Variables that are included are often difficult to interpret without additional information on social and behavioral factors.

The source of the data:

Birth and death certificates and fetal death reports filed with the MDH Office of the Vital Records are the data sources for the reproductive and birth outcomes measures. These data are entered electronically into the Minnesota Registration and Certification (MR&C) system, an integrated, web-based application that electronically records and maintains records on vital events (birth, death, and fetal death) for the State of Minnesota.

Measures are computed using data on births to Minnesota resident mothers, with residency determined by address at time of birth as listed on the birth certificate. Race and ethnicity categories for births are based on the race and ethnicity of the mother as reported on the birth certificate. Hispanic ethnicity includes anyone indicating they are of Hispanic/Latino descent regardless of race.

The National Center for Health Statistics is the source for national numbers on these pages.

How reproductive & birth outcomes are identified:

  • Reproductive and birth outcomes are identified from birth and death certificates and fetal death reports filed with the MDH Office of the Registrar. Fields used from birth certificates include gestational age, birth weight, sex of infant, race of mother, and age of mother. Age at death is obtained from death certificates linked to birth certificates. Fetal deaths are identified from death certificates. Fields used from death certificates include gestational age, race of mother, and age of mother.
  • Preterm: The primary measure used to determine the gestational age of the newborn is the interval between the first day of the mother's last normal menstrual period (LMP) and the date of birth. The due date of a pregnancy is 40 completed weeks following the LMP date. Births occurring before 37 completed weeks are considered preterm. Because the LMP date is missing on many birth certificates, different methods are used to determine gestational age. MDH imputes gestational age when the LMP date is missing or inconsistent with birth weight. The National Center for Health Statistics, which is the source for national numbers on this portal, uses the clinical or obstetric estimate of gestational age when the LMP is not reported or incompatible with the reported birth weight. Measures are calculated by using a denominator that includes cases with missing information for that measure. 
  • Low Birth Weight: Birth weight is the first weight of the newborn obtained after birth. Measures are calculated by using a denominator that includes cases with missing information for that measure.
  • Infant Mortality: Mortality data are calculated using the period linked approach, where all infant deaths occurring in a given data year are linked to their corresponding birth certificates, whether the birth occurred in that year or the previous year. For example, the 2010 mortality data includes all infant deaths occurring in 2010 that have been linked to their corresponding birth certificates, whether the birth occurred in 2009 or in 2010. An alternative method sometimes used is the birth cohort linked file approach, which consists of deaths to infants born in a given year. In both cases, the denominator is all births occurring in the year. 

The difference between a number and a rate, and how to use them:

Number:

  • The number indicates the total number of a reproductive and birth outcome.
  • If you want to understand the magnitude or how the overall burden is, use the number.
  • To protect an individual's privacy, counts from 1 to 5 are suppressed.

Rate:

  • A rate is a ratio between two measures with different units. In our analysis a rate is calculated using a numerator (the number of a reproductive and birth outcome during a period of time) divided by a denominator (the number of people at risk in a population during the same period of time, the number of live births). This fraction is then multiplied by a constant to make the number more legible. The constant is 100 for preterm, very preterm, low birth weight, and very low birth weight (also called percent), or 1,000 for infant mortality measures. Population estimates from the U.S. Census are used to calculate the rate.
  • If you want to understand the probability or what is the underlying risk in a population, then use a rate.
  • To protect an individual's privacy, rates based on counts from 1 to 5 are suppressed.
  • Rates based on counts of 20 or less are flagged as unstable and should be interpreted with caution. These rates are unstable because they can change dramatically with the addition or subtraction of one case.

The limitations of the data:

  • The quality of vital statistics data is directly related to the completeness and accuracy of the information contained in the source documents. MDH maintains two programs to improve the quality of information received on birth and death certificates in order to ensure that the information is as complete and accurate as possible: a query program to contact hospital personnel, funeral directors, and/or physicians concerning incomplete or conflicting information; and a field program focused on educating participants in the vital registration system. MDH also holds birth registration annual conferences to improve birth and death data entry. Estimates of the length of a pregnancy ("gestational age") were included in most Minnesota birth certificate records. The gestational age for 91% of 2010 births was determined by date of last menstrual period (LMP), and less than 0.5% of 2010 births had gestational age imputed due to inconsistency between birth weight and gestational age. In 2010, 6% of all U.S. birth certificates had missing or incompatible gestational age data. Over 11% of all singleton birth records in 2000-2010 were missing gestational age, and this may affect measures of preterm, very preterm and term low birth weight in this report.
  • Timeliness is a limitation of the vital records system. It is not unusual for a birth record to be amended weeks or months after it was originally processed by the Center for Health Statistics due to adoption, correction, or out-of-state birth. Because of the time it takes to correct and amend birth records, the final birth file for a particular calendar year can take many months after the end of the calendar year to close and be made available for epidemiological use. Data on infant deaths takes even longer to be ready for analysis because of the time it takes to link birth and death files.
  • Residential information is very important when examining environmental exposures and other risk factors that may occur before birth. A limitation of the data source is that the place of residence during pregnancy (and, with infant death, residence during first year of life) may not be represented by maternal residence at time of birth (or death). Adoption replaces demographic characteristics of the birth mother (including mother's race/ethnicity, education level, etc.) with those of the adoptive mother. Replacement of birth mother address with adoptive mother address further biases the place of residence data element.

More technical information about the data:

For more about the reproductive and birth outcome data and measures developed by the MN Environmental Public Health Tracking Program, contact Minnesota Public Health Data Access. To learn more about additional reproductive and birth outcomes data available from MDH, contact the MN Center for Health Statistics