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Birth Outcomes - Sex Ratio at Birth

Summary Indicator Report Data View Options

Male to Female Sex Ratio at Birth (Term Singletons Only) by County, New Mexico, 2017-2021

Why Is This Important?

Population growth is, in part, related to the number of liveborn male infants. Information about sex ratio (SR) at birth is also helpful in understanding trends in infant morbidity, such as low birthweight and mortality, as male infants are more susceptible to illness and have higher infant mortality rates (CDC, National Center for Health Statistics, 2005). Although the mechanism that determines an infant's sex is not completely understood, there is evidence that some of the changes in SR are driven by altered sex hormone levels around the time of conception or during gestation. Several environmental exposures have been implicated as possible risk factors for skewed SRs. Exposure to endocrine disrupters (e.g., dioxins, PFAS, BPA, phthalates, and persistent organic pollutants) can result in a decrease in testosterone, and consequently, fewer males are conceived. Associations are more often found between paternal exposures and skewed SR than maternal exposures (CDC NEPHT Program, 2022). A study of 199 million birth records in the United States from 1968 to 2019 found that race/ethnicity had the strongest influence on sex ratio at birth. Asians had the highest SR, and Black and American Indian/Alaska Native had the lowest SR (Sanchez-Barricarte, 2023).

Definition

The ratio of total males to total females born in a pre-defined geographic area at a given time (one birth year or multiple years) is the sex ratio.

Data Sources

  • Birth Certificate Data, Bureau of Vital Records and Health Statistics (BVRHS), Epidemiology and Response Division, New Mexico Department of Health.
    (https://www.nmhealth.org/about/erd/bvrhs/vrp/)
  • Centers for Disease Control and Prevention, National Center for Health Statistics, CDC WONDER Online Database
    (http://wonder.cdc.gov)

How the Measure is Calculated

Numerator:Total number of male infants born in a specified geographic area during a specified time period.
Denominator:Total number of female infants born in a specified geographic area during a specified time period.

How Are We Doing?

The overall SR has remained fairly constant since 2000, with a peak in 2020 of 108.1. In 2021, it dropped slightly to 106.2. There is substantial variability by county, however, with Chaves, Colfax, De Baca, McKinley, and Torrance counties all having a SR < 100, meaning more females than males were born. In contrast, Eddy, Grant, Guadalupe, Hidalgo, Sierra, Socorro, and Union counties all had SR > 110. Asian/Pacific Islanders had the highest SR at 113.6, with American Indian/Alaska Natives having the lowest at 102.5.

How Do We Compare With the U.S.?

In 2020, New Mexico ranked first in the United States with the highest sex ratio at birth of 1,074.1. [Note: National Tracking uses per 1,000 female babies instead of per 100 female babies]

Other Objectives

CDC Environmental Public Health Tracking, Nationally Consistent Data and Measures (EPHT NCDM)

Footnote References

CDC, National Center for Health Statistics, National Vital Statistics System, National Vital Statistics Reports. Trend Analysis of the Sex Ratio at Birth in the United States. 2005;53(20). CDC National Environmental Public Health Tracking Program Indicator: Sex Ratio. https://ephtracking.cdc.gov/indicatorPages Sanchez-Barricarte, JJ. Factors influencing the sex ratio at birth in the United States from a historical perspective. Journal of Biosocial Science. 2023. doi: 10.1017/S0021932022000554 CDC National Environmental Public Health Tracking Program Data Explorer [Content Area: Reproductive & Birth Outcomes; Indicator: Sex Ratio; Measure: Male to Female Sex Ratio at Birth Multiplied by 1,000; Geography Type: National by State; Geography: All States; Time: 2020; Advanced Options: NA] https://ephtracking.cdc.gov/DataExplorer/

Indicator Data Last Updated On 02/01/2023, Published on 05/23/2023
Environmental Health Epidemiology Bureau, Environmental Public Health Tracking Program, Epidemiology and Response Division, New Mexico Department of Health, 1190 S. Saint Francis Drive, Suite 1300, Santa Fe, NM 87505, Srikanth Paladugu, Bureau Chief, Srikanth.Paladugu@doh.nm.gov, or Stephanie Moraga-McHaley, Environmental Epidemiologist Supervisor, Stephanie.Moraga-Mc@doh.nm.gov