Ignore the headlines: aspirin is safe for pregnant women

There are times when published research can have a dramatic positive effect on patient outcomes. There are also times when a study can lead to unnecessary fear mongering, particularly when the results are misrepresented in the press.

new paper has looked at the use of acetaminophen (panadol), aspirin (ASA) and lbuprofen in pregnancy and has ‘found a link’ between cerebral palsy, an irreversible neurological condition, and use of ASA; in simple terms, ASA use is associated with a doubling of the risk of cerebral palsy in the babies of women who use it whilst pregnant.

Cerebral palsy is a neuromuscular disorder with a wide spectrum of manifestations, from a child with mild impairment of movement or coordination to one with a profound disability. Contrary to public perception, the majority of cases are not due to mismanagement during labour or delivery; indeed this proportion does not exceed between 5 and 10 per cent of cases and only then specific forms of the condition. The rest are due to genetic factors or the influence of other conditions during pregnancy. Despite research and attempts to control the risk factors for this condition, the rates have not appreciably decreased over time and it still constitutes a major cause of disability in children and subsequently adults.

This paper has merely established correlation (an unexplained link) and not causatio. Sadly this point will be lost among the furore of justified concern, especially as medical history is replete with examples of ‘links’ that turned out to be direct causes, for example that between smoking and lung cancer.

ASA is a potential life saver in specific obstetrical circumstances where the potential risks are far outweighed by the benefits; a tenuous non-causal link to cerebral palsy should not be part of the decision to use it or to discontinue it.

In women with a history of thrombophilia (specific blood clotting disorders that exponentially raise the risk of pulmonary embolism or clots in the veins of the lung and may play a role in the development of preeclampsia or recurrent miscarriage) it is used as one of the measures to reduce the risk of a woman contracting a pulmonary embolism, the number one cause of maternal death in the UK and in developing countries overall.  It can also be useful in those women who suffer from recurrent miscarriages where a blood-based disorder is found to be the potential cause. In selected women it may also have a role, albeit a small one, in preventing preterm labour.

Its most important use in pregnancy however is in those women who are at high risk of preeclampsia, a multi-system progressive pregnancy disorder that can result in the death or severe disability of mother, baby or both.

Through rigorous application of audit, guidelines and action the UK can be proud of the fact that unlike in many other countries, deaths from this condition rank 5th among the causes of maternal death and continue to decrease. This however is not the case in other jurisdictions and even in the UK all agree that constant vigilance, regardless of past success, is the only way forward.

Multiple trials have found that just by using ASA, the risk of preeclampsia in these women can be cut by 50 to 80 per cent.

When one considers that developing preeclampsia can simply result in a pregnancy ending without any complications, or can also be responsible for stroke, intracerebral haemorrhage (bleeding on the brain), renal failure (kidney failure), rupture of the liver, massive haemorrhage and other complications in the mother, not to mention growth problems in the developing baby or other complications that will require a baby being born preterm, two factors alone that ironically also raise the risk of cerebral palsy (indirectly), one can understand why a paper that postulates a link without elucidating any preliminary or definite causal from existing data can be so potentially troublesome.

There will no doubt be some patients who will now refuse to use ASA in indicated situations and I sincerely hope this will not translate into maternal deaths or severe harm to either mother or baby.

Perhaps however this study will actually stop those clinicians in various parts of the world who prescribe ASA liberally in situations where there is no evidence to recommend their use, from continuing bad practise.

The take home message: 40 years of research have established that ASA is safe for use in pregnancy, that it can contribute towards reducing the risks of pulmonary embolism and recurrent miscarriage in specific populations and that it can reduce the incidence of preeclampsia by up to 80 per cent. No causal link has ever been demonstrated between cerebral palsy and ASA use in pregnancy.

Disclaimer: please do not start or discontinue ASA in pregnancy without discussing it with your doctor first.