Smoking during pregnancy doubles risk of sudden death for baby, study says

CNN  — 

Smoking even one cigarette a day during pregnancy can double the chance of sudden unexpected death for your baby, according to a new study analyzing over 20 million births, including over 19,000 unexpected infant deaths.

The study, published Monday in the journal Pediatrics, analyzed data on smoking during pregnancy from the US Centers for Disease Control and Prevention’s birth/infant death data set between 2007 and 2011 and found that the risk of death rises by .07 for each additional cigarette smoked, up to 20 a day, a typical pack of cigarettes.

By the time you smoke a pack a day, the study found, your baby’s risk of unexpected sudden death has nearly tripled compared with infants of nonsmokers.

“One of the most compelling and most important points that I would take away from the study is that even smoking one or two cigarettes still had an effect on sudden infant death,” said pulmonologist Dr. Cedric “Jamie” Rutland, a national spokesman for the American Lung Association.

While ending a smoking habit should be the goal, the study did find that cutting back on the number of cigarettes was somewhat beneficial. Women who reduced their smoking by the third trimester saw a 12% decrease in sudden death risk; quitting entirely by the third trimester created a 23% reduction in risk.

“Every cigarette counts,” said lead study author Tatiana Anderson, a neuroscientist at the Seattle Children’s Research Institute. “And doctors should be having these conversations with their patients and saying, ‘Look, you should quit. That’s your best odds for decreasing sudden infant death. But if you can’t, every cigarette that you can reduce does help.’ “


Sudden infant death syndrome, known as SIDS, was a frightening, unexplained phenomenon for parents for decades until research discovered a connection between a baby’s sleeping position and the sudden deaths. If babies between 1 month and 1 year of age were put to sleep on their stomachs, the risk of dying of SIDS doubled, according to the American Academy of Pediatrics.

The introduction of the “back to sleep” campaign in 1994 educated parents about the dangers, and the rate of deaths dropped by about 50% when parents began putting babies to sleep on their backs. That was soon followed by recommendations to remove bumpers, blankets, toys and other potentially suffocating clutter from the crib.

By 2010, the rates of SIDS in the United States had fallen to about 2,000 a year, compared with nearly 4,700 in 1993, the American Academy of Pediatrics says.

But while the numbers of babies dying of SIDS decreased, two other types of sudden infant death – ill-defined causes and accidental suffocation – have risen over the past two decades, Anderson said, bringing total deaths to approximately 3,700 a year.

Today, researchers combine the three types of death and call it SUID, short for sudden unexpected infant death.

Research has shown a direct link between mother’s smoking and SUID. According to the American College of Obstetricians and Gynecologists, 23% to 34% cases of SIDS and 5% to 7% of preterm-related infant deaths can be attributed to prenatal smoking.

The costs to children born to smokers are also high. Research has shown a connection between smoking during pregnancy and a higher risk of asthma, infantile colic and childhood obesity. Even secondhand smoke is dangerous to the developing fetus, increasing the risk of low birth weight by as much as 20%.

Just how smoking contributes to SUID is being heavily researched, but a prevailing theory is that it increases levels of serotonin, a neurotransmitter that plays a key role in behavioral arousal and activity. In susceptible infants, it’s possible that serotonin affects the ability of the brain stem to regulate the respiratory system during sleep.

“And maybe that leads to the infant stopping to breathe at night,” said Rutland, who is also an assistant clinical professor of internal medicine at the University of California’s UCRiverside School of Medicine.

Rates of smoking in pregnancy still high

Despite a significant drop in smoking rates in the United States, Anderson says, self-reported statistics show that about 338,000 women smoke during pregnancy each year.

“These numbers are probably on the conservative side,” Anderson said. “Women know they shouldn’t be smoking during pregnancy, and there is a certain population that either denies that they smoke or underestimates the number of cigarettes they smoke.”


Despite the knowledge that smoking can harm their baby, Anderson said, statistics show that 55% of those 338,000 pregnant women are unwilling or unable to stop.

“They do not reduce or quit smoking,” she said. “They just continue smoking at the same rate throughout their pregnancy.”

Yet if no women smoked during pregnancy, the study’s computational models estimate, 800 infant deaths each year could be avoided, Anderson said.

Smoking before pregnancy

The new research, the first to be done in conjunction with Microsoft data scientists as part of the company’s A.I. for Humanitarian Action Initiative, was also the first to look at the impact of smoking before pregnancy.

It wasn’t good news for women who smoke and suddenly find out that they are pregnant.

“If you smoke in the three months before pregnancy and quit by the end of the first trimester, you have more than a 50% greater risk of SUID compared to nonsmokers,” Anderson said.

That risk is still lower than if you smoked throughout pregnancy, she explained, but the overall risk is greater than for those who smoked only before pregnancy or never smoked at all.

“That’s the other take-home message,” Anderson said: “Women who are planning on getting pregnant