Mothers who quit smoking in pregnancy are more likely to light-up again after their baby is born if they feel stressed - according to a new report from the University of East Anglia.
Researchers studied interviews with more than 1,000 new mothers and found that the stress of caring for a newborn, sleepless nights, social pressure, and the idea that they no longer need to protect the baby - all contribute to relapse.
The study also found that women who felt they were being supported by a partner were less likely to start smoking again.
Lead researcher Dr Caitlin Notley, from UEA's Norwich Medical School, said: "More women quit smoking during pregnancy than at any other time - but as many as 90 per cent start again within a year of their baby being born. This is particularly true among women in lower socioeconomic groups.
"We wanted to understand why this happens, and identify ways of preventing it. This is important both for the health of the mother, as well as to stop children being exposed to second hand smoke, and because young people are more likely to start smoking if they grow up with smoking in the family.
"We found that many women see smoking as a way a coping with stress. They also believe that physiological changes influence cigarette cravings, and that they no longer need to protect the baby from smoking's harmful effects."
The study sought to find out what factors influence women to start smoking again after childbirth, as well as what things make it easier or more difficult to stay smoke free.
Dr Notley said: "One of the most striking things that we found is that women's beliefs about smoking are a major barrier to remaining smoke free. Many felt that smoking after the birth of their child was acceptable provided they protected their babies from second-hand smoke. Their focus is, admirably, on the health of the baby, but they often do not think about the long term health consequences for themselves as mothers.
"We also found that women who saw smoking as a way of coping with stress were more likely to relapse. And that feeling low, lonely, tired, and coping with things like persistent crying were also triggers.
"Women reported that cravings for nicotine, which had lessened or stopped during pregnancy, returned," she added.
"In many women, the motivation to stop smoking was linked to their pregnancy - but they didn't see it as stopping for good and adopting a life without smoking. Relapse seemed almost inevitable where women admitted that they didn't quit for themselves.
"Social influences also play a part - particularly because social interaction is especially valued after childbirth. Some women reported that their friends expected a return to smoking which influenced them to start again.
"We particularly noted that it was extremely difficult for women to remain smoke free when their partners smoked."
Supportive partners were cited as key to remaining smoke free, along with personal praise from health professionals.
Dr Notley said: "The majority of women who had successfully remained smoke free said that the support of their partner was a strong factor. Partners who gave up smoking, or altered their own smoking behaviours, were a particularly good influence. And those who helped ease the stress of childcare were also praised by women who had resisted the urge to light up."
The research team also found that women's concept of their own identity was an important factor - with many women seeing smoking as a way of rekindling a sense of themselves as individuals.
"In order for women to continue their lives smoke free after pregnancy, we need to see a cultural shift - where women feel more motivated to remain abstinent, and where they feel more comfortable with the change of identity that motherhood brings. Support from partners is vital, but support from health professionals can be very important as well."
'Postpartum Smoking Relapse - a thematic synthesis of qualitative studies' is published in the journal Addiction on September 10.