Picture of Americia Reproductive Outcomes Fact Sheet
Total Page:16
File Type:pdf, Size:1020Kb
REPRODUCTIVE OUTCOMES QUICK FACTS Of the 6 million pregnancies in the United States Age, genetics, medical each year, approximately 2.2 million end with health, socioeconomic status, behaviors, health miscarriage or stillbirth or are voluntarily care, and environmental exposures all affect the terminated; about a half million babies are born ability to conceive, carry, prematurely; and about 120,000 babies have and deliver a healthy full-term baby.1,2,3 birth defects. The role of environmental exposures in reproductive INTRODUCTION and infant health is complex and not largely More than three million healthy babies are born annually in the United understood. States. The parents’ age, genetics, medical health, socioeconomic status, behaviors, access to health care, and environmental exposures all affect No national database their ability to conceive, carry, and deliver a healthy full-term baby. to track all birth defects Unfortunately, not every woman can become pregnant; not every woman exists. Currently, over 40 who becomes pregnant can carry her baby to full term; and not every states have population- based birth defects baby is born healthy. Identification of the specific risk factors involved surveillance systems and is needed to develop prevention and intervention strategies to prevent participate in the adverse reproductive outcomes. National Birth Defects Prevention Network, Our understanding of what causes adverse reproductive outcomes has a nonprofit organization increased greatly over the past decades. However, there is still much that collects, analyzes, we do not know. In particular, the role of environmental exposures and disseminates birth in reproductive and infant health is complex and largely not understood. defect surveillance data.4 This chapter summarizes our current understanding of environmental risk factors for infertility, adverse birth outcomes, birth defects, and developmental disabilities. We look specifically at the following: • Infertility • Birth defects • Premature (or preterm) births • Low IQ and attention deficit/ • Low birth weight hyperactivity disorder (ADHD) • Fetal and infant death diagnoses and miscarriage REPRODUCTIVE 2 OUTCOMES PICTURE OF AMERICA REPORT 3 Preterm birth and low birthweight are associated with WHAT ARE THE RISK FACTORS compromised health and developmental disabilities, FOR INFERTILITY? and ADHD diagnoses are associated with learning NON-ENVIRONMENTAL RISK FACTORS disabilities. Cancer of the reproductive organs; endometriosis; INFERTILITY sexually transmitted diseases, such as gonorrhea Not all couples can bear children, because of infertility and chlamydia; and other diseases involving the reproductive organs or hormones are known or impaired fecundity. Infertility is the inability 6,7 of a couple to conceive a child. Impaired fecundity to increase the risk of infertility. Physical anoma- encompasses problems conceiving and also problems lies of the reproductive organs may also interfere carrying a pregnancy to term. Each of these conditions with fertility. Although these conditions are gen- contributes to lower birth rates and a lower total fertil- erally considered nonenvironmental risk factors, ity rate. For the purposes of this discussion, infertility environmental exposures could be responsible for is used more broadly to refer to all fertility impairments. causing some of the diseases and anatomical varia- tions. Maternal or paternal alcohol consumption The fertility of an individual male or female is affected and smoking increase the risk of infertility8,9 as do by many factors, including the following: some medicines and drugs, poor diet, athletic train- ing, and being overweight or underweight.1,10 Many • Age comorbidities are also associated with infertility, • Genetics such as obesity11, epilepsy12, injury13,14, eating disor- • Nutrition ders15, and cancer.16 • Behavior • Infections of the reproductive tract ENVIRONMENTAL RISK FACTORS • Stress Numerous chemicals found in the environment are • Some medications suspected to be associated with health conditions known to, or which have the potential to, cause Fertility may also be affected by environmental expo- infertility (Table 1). Studies conducted mostly on sures, although the roles they play in altering fertility animals have shown that exposure to high levels are complex, relatively unexplored, and mostly not of pesticides, phthalates, bisphenol A, dioxins, understood. Even when we know the immediate PCBs, heavy metals, or various organochlorine or reason for infertility (low sperm count, endometriosis, polybrominated chemicals is associated with health etc.), the underlying causes are often unknown. Both problems causing, or sometimes co-occurring with, nonenvironmental and environmental factors are infertility. These problems may include cancer implicated. or physical anomalies of the reproductive organs, reduced sperm counts and quality, and alterations in the female menstrual cycle, among other problems.17-46 HOW ARE WE TRACKING INFERTILITY? No national surveillance system exists to track infertility, although the National Survey of Family Growth collects information on the prevalence of infertility from a representative sample of the U.S. population. This survey has historically addressed infertility only in women, but in 2002, the survey began gathering data on infertility in men.48 REPRODUCTIVE 2 OUTCOMES 3 Table 1. Chemical exposures during adulthood and fertility-related effects (Adapted from Luoma, 200536) Bisphenol A Chlorinated Dioxins/ Heavy Organic PCBs Pesticides Phthalates hydrocarbons furans Metals* Solvents** Abnormal sperm or decreased semen quality Endometriosis Menstrual, estrous, and/or ovulatory irregularities Miscarriage or fetal loss Reduced fertility Chromosomal abnormalities/ changes Hormonal changes *Mercury, manganese, and cadmium ** Benzene, toluene, xylene, perchloroethylene, and others STATUS AND TRENDS • Womenshealth.gov (from the U.S. Department FOR INFERTILITY of Health & Human Services) at www.womenshealth.gov The National Center for Health Statistics reports • Report titled “Challenged Conceptions: Environ- the prevalence of impaired fecundity has been mental Chemicals and Fertility” at increasing. In 2002, nearly 12% (7.3 million) www.prhe.ucsf.edu/prhe/events/ of women aged 15–44 years reported impaired Challenged_Conceptions.pdf fecundity, representing a 2% increase from 1988 49,50 • The Collaborative on Health and the Environment’s and 1995 levels. However, some of the increase toxicant and disease database for reduced fertility may be attributable to aging of the population, Web site at www.database.healthandenvironment. coupled with intentionally delayed childbearing org/index.cfm?id=758 (aging reduces fertility). The number of visits to doctors for infertility concerns is also rising, WHAT ARE ADVERSE BIRTH although these statistics may be influenced by greater availability of infertility services, new treat- OUTCOMES? ment technologies, demographics of the U.S. popu- Most newborns weigh 7 to 10 pounds and are born lation, and couples delaying childbearing.43,45,51,52 after a pregnancy of approximately 40 weeks. How- ever, about 1 in 12 babies is underweight (less than 5.5 ADDITIONAL RESOURCES pounds) at birth, and approximately 1 in 8 newborns is delivered prematurely (less than 37 weeks).53 • MedlinePlus (from the U.S. National Library A small but significant number of babies die before of Medicine) at www.nlm.nih.gov/medlineplus/ delivery or are born live but die before their first infertility.html birthday. Although fewer pregnancies now end REPRODUCTIVE 4 OUTCOMES PICTURE OF AMERICA REPORT 5 in fetal or infant death compared with the death rate birth outcome have an increased risk for a subse- 20 years ago, a higher percentage of births are pre- quent poor birth outcome. Maternal smoking mature, and more newborns are below the optimum and substance abuse increase the risk of low survival weight. birthweight and preterm birth. Social, economic, and neighborhood factors are also associated with The causes for most of these adverse birth outcomes adverse birth outcomes. are not well understood but most likely involve the co-occurrence of multiple factors from many areas ENVIRONMENTAL RISK FACTORS of a woman’s life. Infant mortality is closely associated Exposure of nonsmoking pregnant women to envi- with preterm (premature) birth and low birthweight. ronmental tobacco smoke has been documented Preterm birth is the most frequent cause of infant as a risk factor for preterm birth, low birthweight, mortality, accounting for over one third of infant and possibly miscarriage.55–64 Evidence also deaths. The declining trends in infant death have gen- supports a link between maternal exposure erally been related to advances in medical care, which to components of air pollution (carbon monoxide, increase survival of preterm, low birthweight infants. particulate matter, nitrogen dioxide) with both low Although improvements in medicine have reduced birthweight and preterm birth, even at levels death and disability among infants born too early and below the Environmental Protection Agency’s too small, preterm infants remain at increased risk (EPA) National Ambient Air Quality Standards of illness, developmental disabilities, neurological dis- (see Outdoor Air Quality module).56–74 orders, and other chronic health conditions requiring increased levels of long-term medical care, parental Maternal exposure to lead is associated with pre- care, and special education services.1