Pregnancy, Asthma & Smoking: A Dangerous Threesome

Asthmatic pregnant women who smoke are at greater risk for pregnancy complications than nonsmokers

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Most pregnant women know that it's not wise to smoke while pregnant because of the possible effects on their unborn baby. Not smoking is even more important for asthmatic pregnant women.

A recent study found that several complications were more likely in pregnant women who smoked and had asthma than if they only had one of those risk factors.

This study showed that smoking, asthmatic pregnant women had a higher risk than non-smoking women without asthma for premature birth and urinary tract infections.

In addition, women with asthma or who smoked had a higher risk for hemorrhaging (severe bleeding).

"Don't smoke during pregnancy."

This study, led by Nicolette Hodyl, PhD, of the School of Pediatrics and Reproductive Health at the University of Adelaide in Australia, looked at how pregnant women fared if they had asthma and smoked during their pregnancy.

The researchers examined 172,305 pregnancies involving a single baby that occurred in South Australia between 1999 and 2008.

The researchers determined how many of the women had asthma, how many smoked cigarettes, how much the smokers smoked and what kind of pregnancy complications the women had.

In assessing pregnant women's increased risks for smoking or having asthma, the researchers took into account the women's age, number of previous children, socioeconomic status, history of high blood pressure or diabetes and the year they gave birth.

Overall, 6.7 percent of the women had asthma. While 25 percent of the asthmatic women smoked during pregnancy, only 17 percent of the non-asthmatic women smoked during pregnancy.

The researchers found that pregnant women who had asthma alone were already at an increased risk for a variety of pregnancy complications compared to those who were not asthmatic and didn't smoke.

These complications included gestational diabetes, hemorrhaging (severe bleeding) before giving birth, having too much amniotic fluid surrounding the baby and having their water break early (premature rupture of membranes.)

Other complications that asthmatic women were at higher risk for included needing an emergency cesarean section, having babies who were underweight or small for the pregnancy week when they were born or having babies with birth defects.

Compared to non-asthmatic and non-smoking women, non-smoking women with asthma had about 1.3 times greater odds of gestational diabetes, premature rupture of membranes or a pregnancy complication related to high blood pressure.

Meanwhile, women who smoked during pregnancy, regardless of whether they had asthma or not, were at a higher risk for having their water break early or having too much amniotic fluid around the bay.

Pregnant smokers were also at higher risk for experiencing a hemorrhage before giving birth, compared to non-asthmatic, non-smoking pregnant women.

In the women who smoked, the more cigarettes they smoked each day, the more their risks for these complications increased.

Women who were both asthmatic and smoking had even higher risks for complications. For example, an asthmatic woman had 50 percent increased odds for having too much amniotic fluid around her baby, but a smoking, asthmatic woman had 90 percent increased odds of this complication.

Asthmatic women who smoked during pregnancy were also twice as likely as non-smoking, non-asthmatic women to go into premature labor or to have a premature rupture of membranes (water breaking early).

Smoking asthmatic women had almost three times greater odds than non-smoking, non-asthmatic women of having a placental abruption, in which the placenta separates from the uterus, leading to hemorrhage.

"Notably, maternal asthma combined with cigarette smoking significantly increased the risk of preterm birth and urinary tract infections to a greater degree than with either exposure alone," the researchers wrote.

Andre Hall, MD, an OBGYN at Birth and Women's Care, PA in Fayetteville, NC, said he has unfortunately treated pregnant patients with asthma who also smoke.

"At the risk of sounding less than 'politically correct,' fewer things make less common sense than to smoke if you are a known asthmatic who happens to be pregnant," Dr. Hall said. "As this study shows, most adverse outcomes during pregnancy are worsened when you put together the previously mentioned scenario."

He said it's more challenging for women with asthma to get sufficient oxygen.

"When pregnancy and especially smoking is added, the developing child often does not get enough oxygen for the normal development of many organs including the brain," Dr. Hall said.

"In addition, smoking can serve as a trigger for an asthma attack, which depending on severity, can be life threatening to mom and baby," he said. "If you have asthma and are pregnant, smoking is a very bad idea."

This study was published July 30 in the European Respiratory Journal. The research was funded by a National Health and Medical Research Council Fellowship. No conflicts of interest were noted.

Review Date: 
September 19, 2013
Last Updated:
September 24, 2013