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BJOG release: Smoking in pregnancy “affects boys’ fitness in later life”

News 9 December 2015

Mothers who smoke are putting more than their own health at risk, suggests a study published today in BJOG: an International Journal of Obstetrics and Gynaecology (BJOG). Young men whose mothers smoked during pregnancy had lower aerobic fitness compared to those whose mothers did not.

For the first time, a small Finnish study has examined the impact of maternal smoking on the long-term health of male offspring. Of the 508 young men (average age 19) included in the study 59 of their mothers smoked more than one cigarette a day throughout pregnancy. Results found that maternal smoking was associated with lower aerobic fitness of their children, which was measured by ability on a running test at the beginning of their military service assessment. Aerobic activity was also independently associated with their own smoking status, weight and physical activity.

The study also found that higher maternal pre-pregnancy BMI and excessive weight gain during pregnancy were associated with lower aerobic fitness in the offspring. 

Dr Maria Hagnäs from the University of Oulu, Finland, and lead author of the study said:

"It’s well established that smoking and breathing in second-hand smoke are harmful for both mother and baby. Our study adds to the existing evidence base of the negative and long-standing impacts of maternal smoking. Women must receive advice and support to help them stop smoking during pregnancy, as well guidance on how to maintain a healthy weight to minimise the risks to their unborn child.”

The health risks associated with smoking, and the benefits of stopping smoking, are well known. Mothers who smoke are at a higher risk of miscarriage, ectopic pregnancy, intrauterine growth restriction, premature birth and stillbirth. Their babies are also more likely to suffer from birth defects, and neurological, psychological or behavioural difficulties. In addition, babies born to mothers who smoke have a greater risk of asthma, chest and ear infections and pneumonia as well as being more susceptible to infant death syndrome. Although more likely to be small babies, they are at increased risk of obesity and insulin resistance (the precursor of diabetes) later in life.

Dr Geeta Kumar, Chair of the RCOG’s Patient Information Committee, said:

“Stopping smoking is one of the most important things a pregnant woman can do to improve their baby’s health, growth and development, and this study demonstrates the negative effect smoking in pregnancy can have on  a child’s long-term health too.

“It is important that women understand the risks of smoking in pregnancy and are aware of the support that is available to help them stop. Women who are unable to quit smoking should be encouraged to abstain during their pregnancy, use nicotine replacement therapy, or to reduce smoking as much as they can. We encourage all healthcare professionals working with pregnant women to access the RCOG’s new patient information leaflet which contains practical and evidence-based advice and guidance to share with women about smoking during pregnancy.”


10 things you need to know about smoking in pregnancy

Advice from the Royal College of Obstetricians and Gynaecologists

  1. Smoking is harmful to you and your baby and the best thing you can do to protect your baby’s growth and development is to stop.
  2. The risks to you and your baby include miscarriage, ectopic pregnancy, stillbirth, premature birth, growth and developmental problems.
  3. Stopping smoking at any time during your pregnancy is beneficial to you and your baby.
  4. Passive smoking can also affect your baby’s health – ask smokers to refrain from smoking around you.
  5. You will be asked about smoking during your first antenatal appointment, you should be open and honest with your midwife so that you can get support as early as possible during your pregnancy.
  6. There are support schemes available to help you and your partner or close family member stop smoking – this involves a 12 week programme including one-to-one appointments with a specialist midwife or stop smoking adviser and advice on how to cope with cravings and withdrawal symptoms.
  7. Nicotine Replacement Therapies (NRT) are safe to use during pregnancy
  8. Electronic cigarettes are not recommended for use during pregnancy, this is because they are not controlled and have been found to contain harmful substances as well as nicotine.
  9. Four out of five women who manage to stop smoking for 28 days, do so for good.
  10. Smoking may also affect your fertility and the quality and amount of breast milk you produce.

For media enquiries, please contact Hilary Glover, RCOG Media and PR Officer on 020 7772 6357 or email


NHS Smokefree:

Smoking in Pregnancy Challenge Group:


How to contact a stop smoking adviser:

Your GP can refer you, or you can phone your local NHS Stop Smoking Service to make an appointment with an adviser:

England: or call the free Smokefree National Helpline on 0300 123 1044.

Scotland: or call the free Smokeline on 0800 84 84 84. 

Wales: or call the free Stop Smoking Wales Helpline on 0800 085 2219.

Northern Ireland: or call the free Smokers’ Helpline on 0808 812 8008.

RCOG patient information leaflets: 

Smoking and pregnancy

Ectopic pregnancy:

Having a small baby:

Premature labour:

BJOG: An International Journal of Obstetrics and Gynaecology is owned by the Royal College of Obstetricians and Gynaecologists (RCOG) but is editorially independent and published monthly by Wiley. The journal features original, peer-reviewed, high-quality medical research in all areas of obstetrics and gynaecology worldwide. Please quote ‘BJOG’ or ‘BJOG: An International Journal of Obstetrics and Gynaecology’ when referring to the journal and include the website: as a hidden link online.

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Royal College of Obstetricians and Gynaecologists - Bringing to life the best in women’s healthcare. The RCOG is a medical charity that champions the provision of high quality women’s healthcare in the UK and beyond. It is dedicated to encouraging the study and advancing the science and practice of obstetrics and gynaecology. It does this through postgraduate medical education and training and the publication of clinical guidelines and reports on aspects of the specialty and service provision.


MP Hagnäs, H Cederberg, J Jokelainen, I Mikkola, U Rajala, S Keinänen-Kiukaanniemi. Association of maternal smoking during pregnancy with aerobic fitness of offspring in young adulthood: a prospective cohort study. BJOG 2015; DOI: 10.1111/1471-0528.13789