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Maternal risk factors in Texas vary dramatically from one zip code to the next, according to new study

AUSTIN – Maternal risk factors vary dramatically in Texas by zip code, according to a new report and searchable maps from The University of Texas System and UT Health Science Center at Tyler.


Using all Texas birth records for 2015, researchers calculated zip code-level measures for smoking during pregnancy, pre-pregnancy obesity, and utilization of prenatal care for zip codes in which there were 100 or more births.


“As Texas moves forward with efforts to improve maternal health, it is important that we understand how some of the key risk factors vary widely even within cities,” said David Lakey, MD, Vice Chancellor for Health Affairs and Chief Medical Officer for UT System. “This will allow us to target efforts where they’re most needed.”


The study of maternal risk factors based on zip code follows a similar report that looked at infant mortality, which was released in January.


One marker of a mother’s health as she becomes pregnant is her pre-pregnancy body mass index (BMI). Women who are in the obese range of BMI when they become pregnant are at an increased risk for a variety of dangerous complications during pregnancy. The risks are even greater for women who are morbidly obese (a BMI greater than 40, or roughly 100 pounds heavier than ideal weight).


The prevalence of pre-pregnancy obesity ranged from 10 percent in some zip codes to more than 40 percent in others. While pre-pregnancy morbid obesity is less common and shows less variability, in 2015 the prevalence was more than 10 percent in some Texas zip codes.


There is also dramatic variation within racial and ethnic groups and within communities. In Bexar County, in 2015, the percentage of babies born to Hispanic women who were classified as morbidly obese prior to becoming pregnant ranged from a low of 1.1 percent to a high of 9.3 percent.


Smoking during pregnancy is associated with a range of maternal and infant health risks, including premature birth, low birth weight, and certain birth defects, and may increase a child’s risk of obesity, asthma, and high blood pressure later in life. Overall, the proportion of women who smoke during pregnancy in Texas is one of the lowest in the country. That overall rate, however, obscures high rates in various parts of the state.


In 2015, 12 percent of the included zip codes had more than 10 percent of their infants born exposed to prenatal maternal smoking, while the highest prevalence for any included zip code was 25.4 percent.

Within the Dallas/Fort Worth Metroplex, in 2015, the percentage of babies born to white women who smoked at any time during their pregnancy ranged from a low of 0 percent to a high of 25.5 percent.

Prenatal care is important to the health of the mother and the baby. During these visits, women with chronic health conditions or complications during pregnancy can be medically managed to reduce the negative outcomes for the baby.


In half of the zip codes in the state with at least 100 births in 2015, fewer than 2 percent of infants’ mothers had no documented prenatal care. In 5 percent of zip codes, however, more than 10 percent of births in 2015 were to a mother who had not received any prenatal care before birth.


Within zip codes with at least 100 births to black mothers in 2015 in Harris County, the percentage of babies born to black women with no documented prenatal care during their pregnancy ranged from a low of 0 percent to a high of 10.1 percent.


Although the data and map show the wide geographic variation in the state, they do not show why the variation exists. Researchers with UT System will continue to work towards understanding why this variation exists and what can be done to improve maternal health overall. UT System is also making public use data files available, as well as other technical information, to facilitate work by other researchers.


“There is no silver bullet for improving maternal health in Texas,” said Lakey. “What’s required are a range of approaches, informed by data and evidence. This work is intended to assist these efforts.”


About The University of Texas System
Educating students, providing care for patients, conducting groundbreaking basic, applied and clinical research, and serving the needs of Texans and the nation for more than 130 years, The University of Texas System is one of the largest public university systems in the United States. With 14 institutions and a projected enrollment of more than 234,000 students, the UT System confers more than one-third of the state’s undergraduate degrees, educates approximately two-thirds of the state’s health care professionals annually and accounts for almost 70 percent of all research funds awarded to public institutions in Texas. The UT System’s operating budget for FY 2018 is $18.3 billion, funded in part by $3.6 billion in sponsored programs from federal, state, local and private sources. With more than 20,000 faculty – including Nobel laureates and members of the National Academies – and nearly 80,000 health care professionals, researchers, student advisors and support staff, the UT System is one of the largest employers in the state.

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