A new study published Wednesday, March 16, in the journal Addiction paints a bleak picture about the realities of trying to quit smoking while pregnant.

The authors, primarily hailing from the University of Nottingham in the United Kingdom, analyzed the success rates of past randomized studies that tried to help pregnant smokers quit. Pooling these results, they determined that nearly all the women who sought out cessation interventions, 87 percent, had returned to smoking by the end of pregnancy. For those who didn’t, 43 percent had relapsed within six months of giving birth, leaving 94 percent of women in total who failed to quit long-term.

“Most pregnant smokers do not achieve abstinence from smoking while they are pregnant, and among those that do, most will restart smoking within six months of childbirth,” the authors wrote. “This would suggest that despite large amounts of health care expenditure on smoking cessation, few women and their offspring gain the maximum benefits of cessation.”

The researchers conducted two different analyses. In the main one, they looked at 11 studies that provided data on how long the participants stayed clean throughout the entire length of the pregnancy and at least up to six months after. In the second, which they only used to judge how many women had relapsed by pregnancy's end, they evaluated data from 23 studies that measured abstinence at certain points of time during and after pregnancy.

While the latter type of study is still useful to measure smoking cessation, it can sometimes be misleading. For instance, someone who is tested for or asked to confirm their abstinence every four weeks can still smoke in between each session, especially since most tests only measure abstinence going back the past seven days. For that reason, the researchers felt they couldn’t “guarantee that women reporting abstinence at postpartum follow-up would be the same women as those reporting abstinence at the end of pregnancy.”

The review is purportedly the first to systematically quantify how often women go back to smoking post-partum. Since the researchers measured women who volunteered for clinical trials, — those already highly motivated to quit smoking — the authors believe their findings apply to women who seek out dedicated support services to quit.

Unfortunately, as the researchers hypothesize, that distinction may only mean quitting is much harder for these women in particular. That’s a theory supported by individual studies showing that women who quit spontaneously upon finding out they’re pregnant have abstinence rates of 38 to 62 percent by the time they deliver their child, compared to the 13 percent observed by the current review.

As with most smokers, neither pregnant women who quit spontaneously nor those with dedicated support seem to have much luck staying tobacco-free for too long, however. As lead author Dr Matthew Jones points out, it’s a failure with a heavy toll.

"Smoking during pregnancy is a major global public health issue: A conservative estimate for the annual economic burden in the UK is £23.5 million and in the U.S, $110 million,” he said in a statement. “Our report reveals a wide gulf between what pregnant women need to quit smoking and what our health care services currently provide."

Of course, smoking during pregnancy is also linked to a wealth of health issues for the soon-to-be child.

Source: Jones M, Lewis S, Parrott S, et al. Re-starting smoking in the postpartum period after receiving a smoking cessation intervention: a systematic review. Addiction. 2016.