Michael Turner
Helping secret smokers come clean can reduce risks during pregnancy
MATERNAL smoking is arguably the most important modifiable risk factor for pregnancy in Ireland. It is important because it is common, it compromises foetal growth and development and it increases the risk of maternal complications. Finally, it is important because if the mother quits smoking before the second half of pregnancy, her baby’s growth and development normalise.
Nearly half of adults in Ireland smoke at some stage in their lives. The number of current smokers is falling, albeit slower than we would like. Most women start smoking as teenagers and many stop smoking without any medical assistance before they become pregnant or as soon as they realise they are pregnant. In a recent large research project at the UCD Centre for Human Reproduction, Ciara Reynolds and her colleagues found that 12.5pc of women over five years disclosed to the midwife that they were persistent smokers when they first presented to the Coombe Women and Infants University Hospital for antenatal care. However, in a smaller study women were given a more detailed smoking questionnaire and were offered a breath carbon monoxide (BCO) test.
A BCO test is similar to the breathalyser used to detect alcohol in drivers. It is safe, inexpensive, non-invasive and gives an immediate read out at the point of care. It is a sensitive measure of smoking within the last six hours. This study found that one in 10 women continued to smoke during pregnancy but did not disclose it to the midwives or doctors. Interestingly, women who did not disclose their smoking were more likely to have planned their pregnancy, to be light smokers and to be better educated than women who disclosed. Their reluctance to disclose is unexplained.
The research in the UCD centre has shown that, compared with 13.1pc in nonsmokers, women who disclose their persistent smoking during pregnancy have a 19.4pc risk of adverse foetal events. However, women who did not disclose their smoking had a 34.8pc risk of adverse events.
Cigarette smoke contains about 4,000 different chemicals and many of them are known to be toxic and to reduce blood flow. After a puff of a cigarette, these chemicals reach the brain within 10-15 seconds, which provides immediate relief in cases of nicotine addiction. Unfortunately, these chemicals also reach the foetal circulation quickly. A woman who takes 10 puffs per cigarette from 10 cigarettes per day, therefore exposes her baby to the different toxins on 100 occasions. It also compromises the placental blood flow to the baby 100 times.
The combination of toxins and reduced blood flow restrict the growth of the baby. At its most catastrophic, growth restriction may result in a stillbirth. Any growth restriction, however, reduces birth weight, increases foetal distress and increases the need for admission to the neonatal intensive care unit which may increase the hospital stay for the baby.
If a mother is a known current smoker, she should be monitored closely in the third trimester for inadequate foetal growth. The monitoring should include at least one scan to check the baby’s weight and well-being. If the scan identifies a problem, it may be necessary to deliver the baby early by induction of labour or caesarean section. If a mother does not disclose her smoking, the inadequate foetal growth may not be identified. Although unintended, non-disclosers are putting their babies at increased risk.
In the UK, it is recommended that all pregnant women are offered BCO screening at the first antenatal visit. A recent audit in Ireland found that only one out of 19 units was offering screening. This needs to be remedied nationally.
It is important to reassure women that BCO screening in pregnancy is not intended to penalise or to end in a chastisement from their midwife or doctor. The opposite is true.
Screening should lead to better support for women to help them stop smoking and prevent relapses. Even if they do not succeed in quitting during the pregnancy, renewed efforts at cessation can be made after delivery. Screening should lead to close foetal surveillance until the end of pregnancy.
Many smokers find pregnancy stressful. The staff in the maternity units are there to support women as pregnancy advances. Admonishment of women about smoking and other lifestyle issues is likely to be counterproductive and may lead to a reluctance to disclose risk factors in general.
Women who need assistance to quit smoking can contact the HSE Quit service through their website quit.ie, Freephone 1800 201 203 or free text quit to 50100.
Women who did not disclose their smoking were likely to be better educated than those who did