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Important Facts for Birth Outcomes: Sex Ratio at Birth


The ratio of total males/total females born in a geographic area at a certain time.


The total number of full-term, singleton male infants born in a specified geographic area during and time period.


The total number of full-term, singleton female infants born in a specified geographic area during and time period.

Why Is This Important?

Population growth is, in part, related to the number of live male children. Numerous studies have reported changes in the ratio of males to females at birth; many of the studies have found a reduction in male relative to female births in different countries throughout the world. Although the mechanism which determines the sex of the infant is not completely understood, some, but not all, have suggested that environmental hazards can affect how many males are born. Biological parent(s) and/or the fetus can come in contact with and become exposed to different hazards referred to as endocrine disruptors. Fewer males are conceived when exposure to endocrine disruptors results in a decrease in testosterone. Because states have accurate Vital Statistics (VS) records on the sex of live births, changes over time in the sex ratio of infants can be measured as the ratio of males to females.

Other Objectives

CDC Environmental Public Health Tracking, Nationally Consistent Data and Measures (EPHT NCDM)
The information provided above is from the New Mexico Department of Health's NM-IBIS web site ( The information published on this website may be reproduced without permission. Please use the following citation: "Retrieved Sun, 17 October 2021 from New Mexico Department of Health, Indicator-Based Information System for Public Health Web site:".

Content updated: Thu, 5 Jun 2014 18:11:36 MDT