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Reproductive and Birth Outcomes - Frequently Asked Questions

What is reproductive and birth outcomes tracking?

Reproductive and birth outcomes tracking is the ongoing collection, analysis, and interpretation of reproductive and birth outcome data. Currently, the Massachusetts Environmental Public Health Tracking (MA EPHT) program tracks data statewide and at the county, community, and census tract levels on premature births and low birth weight, mortality, fertility, and sex ratio occurring beginning in 2000.

What are the reproductive and birth outcome measures used by MA EPHT?

There are fourteen measures that are used by MA EPHT to track reproductive outcome data:

Premature Births (preterm)

  • Annual number and percent of premature (less than 37 complete weeks gestation) live singleton births by state and county
  • Average annual number and percent of very premature (less than 32 complete weeks gestation) live singleton births by state and county over a 5 year period

Low Birth Weight

  • Annual number and percent of low birthweight (<2,500 grams) term, singleton live births by state, county, community, and census tracts
  • Average annual number and percent of low birthweight (<2,500 grams) term, singleton live births by state, county, community, and census tracts over 5 year period
  • Annual number and percent of very low birthweight (<1500 grams) term, singleton live births by state, county, community, and census tracts
  • Average annual number and percent of very low birthweight (<1500 grams) term, singleton live births by state, county, community, and census tracts over 5 year period

Mortality

  • Average annual number and rate per 1,000 live births of perinatal (≥ 28 weeks gestation plus infants less than 7 days old) mortality by state, county, community, and census tracts over 5 year period
  • Average annual number and rate 1,000 per live births of infant (<1 year of age) deaths by state, county, community, and census tracts over 5 year period
  • Average annual number and rate per 1,000 live births of neonatal (<28 days of age) deaths by state, county, community, and census tracts over 5 year period
  • Average annual number and rate per 1,000 live births of postneonatal (≥ 28 days to <1 year of age) deaths by state, county, community, and census tracts over 5 year period

Fertility

  • Annual total fertility rate per 1,000 women of reproductive age by state, county, community, and census tracts

Sex Ratio

  • Annual male to female sex ratio at birth (term, singleton live births only) by state, county, community, and census tracts

Why is the MA EPHT program tracking reproductive outcome data?

In 2002, Massachusetts was one of seven states across the U.S. to be awarded funds from the U.S. Centers for Disease Control and Prevention (CDC) to track health conditions thought to be impacted by the environment. Identifying populations with higher premature and low birth weight births; higher infant, perinatal, neonatal, and postneonatal mortality rates; lower fertility rates; and abnormal sex ratios may provide leads on where to look for potential environmental problems.

What is a rate?

A rate is a measure of the frequency with which a disease or health outcome, such as low birth weight, occurs in a defined population during a specific time frame.

What environmental exposures are believed to affect reproductive and birth outcomes?

Studies have shown that exposure to air pollution or drinking water contaminated with chemical disinfection by-products, lead, some solvents, pesticides, di-ethylhexyl phthalate (DEHP), and polycyclic aromatic hydrocarbons (PAHs) is associated with premature and low birth weights.

High versus low concentrations of particulate matter (PM10) were associated with 10% increase in early postneonatal mortality in a study of 4 million infants born in the U.S. between 1989 and 1991. The major causes of death associated with PM10 exposure were deaths from respiratory causes and SIDS.

It has been suspected that low-level exposures to a number of compounds, such as phthalates, polychlorinated biphenyls (PCBs), dioxin, pesticides, and other endocrine disrupting compounds may affect human fertility. Fewer males are conceived when exposed to endocrine disruptors. The medication diethylstilbestrol (DES) has also been though to adversely affect fertility rates.

What are the known and/or potential risk factors for premature births (preterm births)?

  • Carrying multiple fetuses (twins, triplets, or more)
  • Having a previous premature birth
  • Problems with the uterus or cervix
  • Chronic maternal health problems, including high blood pressure, diabetes, and clotting disorders
  • Certain infections during pregnancy
  • Cigarette smoking, alcohol use, or illicit drug use during pregnancy
  • Exposure to second-hand smoke during pregnancy
  • Mother’s age and race
    • African-American women, women younger than 17 years old or older than 35 years, and poor women are at greater risk than other women
  • Male babies, associated with singleton premature birth
  • Certain lifestyle factors
  • Late or no prenatal care
  • Social and economic factors, such as domestic violence, lack of social support, low income, or stress
  • Long working hours or long periods of standing during pregnancy
  • Being underweight or overweight before pregnancy
  • Time between births, less than 6-9 months between birth and the beginning of the next pregnancy
  • Exposures to air pollution or lead and some solvents in drinking water during pregnancy

What are the known and/or potential risk factors for low birth weight births?

  • Cigarette smoking, alcohol use, or illicit drug use during pregnancy
  • Inadequate maternal weight gain during pregnancy
  • Infections in the fetus
  • Babies with certain birth defects
  • Placental problems that limit nutrients to the fetus
  • Social and economic factors, such as low educational level, low income, stress, and domestic violence
  • Mother’s age and race
    • African-American women and women younger than 17 years old or older than 35 years are at greater risk than other women

What are the known and/or potential risk factors for infant neonatal and postneonatal deaths?

  • Premature or low birth weight baby
  • Baby's exposure to secondhand smoke after birth [increases risk of Sudden Infant Death Syndrome (SIDS)]
  • Congenital birth defects
  • Respiratory Distress Syndrome
  • Smoking during pregnancy and/or exposure to secondhand smoke during pregnancy
  • Alcohol or illicit drug use during pregnancy
  • Mother's medical risk factors
    • Anemia
    • Diabetes
    • Pregnancy-induced hypertension
    • Inadequate nutrition and insufficient intake of folic acid (a B vitamin) before and during pregnancy
    • Infections during pregnancy - including reproductive tract infections, sexually transmitted diseases, and periodontal (oral) infections
  • Complications of pregnancy/labor
    • Cord prolapse
    • Placenta previa
    • Abruptio placenta

What are the known and/or potential risk factors for infertility?

  • Age:
    • Women: mid-30s or older
    • Men: over 40 years of age
  • Alcohol use:
    • Women: There is no safe level of alcohol use during conception or pregnancy
    • Men: Heavy alcohol use can decrease sperm count and motility
  • Physical Activity and Overweight
    • Women: An inactive lifestyle and being overweight may increase the risk of infertility
    • Men: An inactive lifestyle and being overweight may decrease sperm count
  • Underweight:
    • Women: Risk of fertility problems for those with eating disorders, such as anorexia or bulimia and for women who follow a very low calorie or restrictive diet
  • Environmental factors: On the job exposure to pesticides, solvents, lead, cadmium, mercury, ethylene oxide, vinyl chloride, radioactivity, and x-rays may reduce sperm count. Motility and exposure to endocrine disruptors in cosmetics and other household products may affect fertility
  • Thermal factors: Exposure of the male genitals to elevated temperatures, such as through hot baths, whirlpools and steam rooms

What are the known and/or potential risk factors for affecting sex ratio (i.e., reduction in the number of male births)?

  • Smoking by a mother and/or father
  • Length of gestation
  • Age of mother and/or father at conception
  • Higher birth order
  • Exposure to environmental chemicals such as endocrine disruptors.

What is the Total Fertility Rate?

The Total Fertility Rate (TFR) indicates the average number of births to a hypothetical cohort of 1,000 women if they experienced the age-specific birth rates observed in a given year. The total fertility rate differs from the general fertility rate (GFR) (# of live births/women of reproductive age 15-44) in that it adjusts for age-specific differences in fertility and shows the potential impact of current fertility patterns on reproduction allowing for more valid comparisons of rates across time and space.

How are reproductive and birth outcome data collected?

Birth and reproductive health outcome data are collected by the Registry of Vital Records and Statistics. Medical data, such as birth weight and gestational age, are based on information supplied by hospitals and birthing facilities. Demographic and behavioral data, such as race and ethnicity and smoking during pregnancy, are supplied by the women who gave birth.

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