Pregnant women who never use cigarettes but breathe in large amounts of secondhand smoke are more likely to lose their babies through miscarriages, stillbirths and ectopic pregnancies, a new study by Buffalo researchers shows.
Numerous studies have found a link to pregnancy loss among pregnant women who smoke, but the evidence for secondhand smoke exposure has been limited and inconclusive.
The latest research is note- worthy because it continued to show the bad pregnancy outcomes in smokers; looked at lifetime exposure to secondhand smoke, not just during pregnancy or reproductive years; and used a comparison group of nonsmokers who reported that they never had exposure to secondhand smoke.
The study sample is also very large, giving its findings statistical power.
The research in the journal Tobacco Control involved 80,762 women, making it the largest examination so far of the effect of secondhand smoke on pregnant women.
The findings suggest that women, especially pregnant women, should avoid secondhand smoke.
“At its most basic level, that is the message of the study,” said Andrew Hyland, chairman of the Roswell Park Cancer Institute Department of Health Behavior and the lead investigator.
“But the research also changes the profile of who is being harmed by tobacco smoke,” he said.
“Most everyone associates secondhand smoke with cancer or heart disease, diseases of older people.
“We’re showing that there is a whole other class of disease and others being harmed – unborn babies.”
For nonsmoking women exposed to the highest levels of secondhand smoke, the study reported a 17 percent higher risk of miscarriage, a 55 percent higher risk for stillbirth and a 61 percent higher risk of ectopic pregnancy, a complication when a fertilized egg implants outside the uterus.
Those risks approached the risks seen among women who smoked more than 100 cigarettes in their lifetime, the researchers said.
The highest level of lifetime secondhand smoke exposure was defined by childhood exposure for longer than 10 years, adult home exposure for more than 20 years and adult work exposure for more than 10 years.
Secondhand smoke from tobacco exposes individuals to hundreds of toxic chemicals, although at lower levels than what a smoker experiences.
It consists of sidestream smoke, the smoke released from the burning end of a cigarette, and mainstream smoke, the smoke exhaled by a smoker.
“The significance of the study is that it shows that secondhand smoke is more harmful than previously thought, not just during pregnancy but over a woman’s lifetime,” said Vince Willmore, vice president for communications at the Campaign for Tobacco-Free Kids in Washington, D.C.
The percentage of nonsmokers exposed to secondhand smoke has declined over the last few decades, particularly with the passage of laws that ban smoking in restaurants, bars and public places.
Nevertheless, secondhand smoke remains a major cause of sickness and death, public health officials say.
Secondhand smoke is responsible for an estimated 42,000 deaths a year in the U.S., according to the federal Centers for Disease Control and Prevention.
“Hopefully, information like this will encourage people who smoke to be more sensitive about smoking in the house,” said Gary Giovino, chairman of the University at Buffalo’s Department of Community Health and Health Behavior.
Giovino, principal investigator of a 2012 global survey of tobacco use, said there is some evidence that the passage of indoor air laws encourages people to make their homes smoke-free.
“The laws may be setting a tone,” he said.
Willmore said the research, from his organization’s perspective, underscores the need for more states to pass comprehensive indoor-air laws. Twenty-four states and the District of Columbia have such laws.
The study relied on data collected in the federally funded Women’s Health Initiative, which interviewed thousands of women ages 50 to 79 years old at centers around the country from 1993 to 1998 in the largest-ever health study of postmenopausal women.
Participants in the Women’s Health Initiative came from a broad range of geographic areas and had multiple ethnic, educational and socioeconomic backgrounds, allowing for a comprehensive assessment of their exposure to tobacco smoke and the outcomes, said coauthor Jean Wactawski-Wende, a UB professor of social and preventive medicine and obstetrics and gynecology.
The limitations of the secondhand smoke study include the potential that the women under-reported their lifetime exposure to tobacco smoke.
Health problems associated with secondhand smoke
• Middle ear diseases
• Respiratory illness
• Sudden infant death syndrome
• Nasal irritation
• Lung cancer
• Coronary heart disease
• Reproductive effects in women
Source: 2014 Surgeon General’s Report