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INTRODUCTION

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In studying male reproductive toxicants, the ultimate aim is to protect the reproductive health of men and the health of their offspring, which is fundamentally important for the health of future generations. The occurrence of adverse reproductive outcomes is of great concern to the individuals and families involved. This is especially true if the individuals perceive that they are living or working in areas with potential exposure to hazardous agents. Adverse reproductive effects can be very stressful for affected families. Existing human information on this subject is very sparse and inadequate for the reproductive assessment of most suspect compounds and physical agents.

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Another reason to better understand male reproductive functions is that they may act as sentinels for detecting occupational and environmental hazards. Reproductive effects have a relatively short latency between exposure and detectable health event (such as abnormal semen profile) as compared with the long latency for cancer. If workers or community residents are protected from exposures that are harmful to reproduction, they usually will be protected from other health effects associated with these exposures as well. While the extent to which workplace and environmental hazards affect reproductive function is unknown, these hazards are potentially preventable. Measures that can be taken to prevent further exposure include substitution or containment of the suspect hazard. Thus, preventing exposure should play a primary role in the health care provider's overall assessment of the patient's situation.

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REPRODUCTIVE OUTCOMES & RATES

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Definitions

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A number of adverse reproductive effects may result from male exposure to chemical and physical agents. These effects range from infertility to birth defects in the infant. Infertility is present when a couple has not conceived after 1 year of unprotected sexual intercourse. Male sexual dysfunction may involve changes in libido (interest in sexual activity), erectile dysfunction, or ejaculatory problems. Semen abnormalities can include azoospermia (complete absence of sperm), oligospermia (decreased sperm count), teratospermia (abnormally shaped sperm), and asthenospermia (sperm showing decreased motility). Abnormal birth outcomes include spontaneous abortion (fetal loss prior to the 28th gestational week), stillbirth (fetal loss after the 28th week), death (infant: younger than 1 year of age; neonatal: younger than 28 days of age; or postneonatal: 28 days to 11 months of age), congenital defect (abnormal appearance or function at birth), prematurity (birth prior to the 37th week of gestation), low birth weight (weight <2500 g at birth), and very low birth weight (weight <1500 g at birth).

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Population Rates

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Precise rates for these types of pregnancy loss are difficult to obtain because of a lack of national monitoring systems and methodologic differences in individual epidemiologic studies. Nevertheless, a range of prevalence rates can be estimated (Table 29–1). Approximately 10% of couples in the United States are infertile. Additional couples may experience periods of subfertility or delayed conception. After conception, a variety of reproductive losses may occur at any time from conception up to full term. Up to 50% of ...

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