By Pat Anson, PNN Editor

Pregnant women who take over-the-counter pain relievers are one-and-a-half times more likely to have complications, including stillbirth and premature delivery, according to a large new study.

Researchers at the University of Aberdeen analyzed data from over 151,000 pregnancies in the UK from 1985-2015, looking for medical notes indicating the women used paracetamol (acetaminophen), aspirin or the non-steroidal anti-inflammatory drugs (NSAIDs) diclofenac, naproxen and ibuprofen — either alone or in combinations.

The findings, recently published in BMJ Open, show a significantly higher risk of a preterm delivery, neonatal death, low birth weight and other health problems in babies born to mothers who used OTC pain relievers. Neural tube defects of the brain, spine or spinal cord were 64% more likely; while hypospadias, a birth defect affecting the penis, was 27% more likely.

“Over-the-counter analgesics consumption during pregnancy was associated with a substantially higher risk for adverse perinatal health outcomes in the offspring. The use of paracetamol in combination with other non-steroidal anti-inflammatory drugs conferred the highest risk,” wrote lead author Aikaterini Zafeiri, PhD. “The increased risks of adverse neonatal outcomes associated with non-prescribed, over-the-counter, analgesics use during pregnancy indicate that healthcare guidance for pregnant women regarding analgesic use need urgent updating.”

One of the more surprising aspects of the study is how use of the five analgesics by pregnant women grew dramatically over the 30-year study period.  In 1985, only 1.8% reported using one of the pain relievers. By 2015, that had grown to 70.6% -- with most of the increase coming in the last seven years of the study.

Although it is believed to be one of the largest and most comprehensive studies of its kind, the research was limited. The duration, dose and stage of the pregnancy when analgesics were consumed were not recorded. The health of the mothers and babies later in life was also not studied.

But given the substantial increase in analgesic use during pregnancy and the higher risk of complications, researchers say more caution is needed on use of the drugs.

“The ease of access to non-prescription painkillers, in combination with availability of misinformation as well as correct information through the internet, raises safety concerns,” said Zafeiri. “It should be reinforced that paracetamol in combination with NSAIDs is associated with a higher risk and pregnant women should always consult their doctor or midwife before taking any over-the-counter drugs. We would encourage a strong reinforcement of the official advice for pregnant women.”   

Previous studies have linked prenatal use of paracetamol to autism, hyperactivity and behavioral problem in children. Despite the findings, drug regulators in the UK and US maintain that it is safe for pregnant women to use paracetamol (acetaminophen).

“Paracetamol is the first choice of painkiller if you're pregnant or breastfeeding. It's been taken by many pregnant and breastfeeding women with no harmful effects in the mother or baby,” the UK’s National Health Service (NHS) says on its website.

The Food and Drug Administration also does not caution pregnant women about using acetaminophen. The agency said in 2015 that the evidence was “too limited” to justify such a warning.  

Meanwhile, drug regulators in Australia are so concerned about recent deaths involving paracetamol that they may restrict access to the drug. Australia’s Therapeutic Goods Administration (TGA) has commissioned a report by an expert panel on the risks of paracetamol misuse.

“While paracetamol has well established safety and toxicity profiles, the wide use is paralleled by a high prevalence of accidental and deliberate paracetamol poisoning in the community, in both adults and children,” the TGA said in a statement earlier this month.

“The TGA is aware of concerns, particularly of families and healthcare professionals of affected consumers of paracetamol, regarding the number of poisonings and deliberate overdoses from paracetamol obtained from general retail outlets, and whether current access restrictions are appropriate.”

Australia currently regulates the quantity and dose of paracetamol sold over-the-counter. The independent commission will consider if stricter buying limits should be imposed.