Women taking anti-inflammatory painkillers, along with hormonal contraception, appear to be at a slightly increased risk of blood clots, known as venous thromboembolism, according to a large study conducted in Denmark and published in the journal “The BMJ”. The risk was greater in women using combined oral contraceptives containing a third- or fourth-generation progestin, but lower in women using only progestin in pills, implants and IUDs. Also, the association was stronger for women taking diclofenac compared to ibuprofen and naproxen.

The researchers stress that the absolute risk of a serious blood clot is low, even in women using high-risk hormonal contraception. But given the widespread use of both hormonal contraception and non-steroidal anti-inflammatory drugs, they emphasize that women should be informed about this potential drug interaction.

For research scientists used national medical records to track first-time VTE diagnoses among two million women aged 15-49 living in Denmark between 1996 and 2017 who had no history of blood clots, cancer, hysterectomy or fertility treatment.

However, they note that the research has several limitations, such as the lack of information on smoking and obesity, which may affect the results.