Women who consume commonly used Ibuprofen even for just two days during the first 24 weeks of their pregnancy may reduce their daughter's number of eggs, potentially affecting their fertility in the future, new research has warned.

The research carried out on human cells in the laboratory revealed that exposure to Ibuprofen during the crucial first three months of foetal development results in a "dramatic loss" of the germ cells that go into making the follicles from which female eggs develop.

The germ cells would either die or fail to grow and multiply at the usual rate. "We found that two to seven days of exposure to Ibuprofen dramatically reduced the germ cell stockpile in human foetal ovaries during the first trimester of pregnancy and the ovaries did not recover fully from this damage," said Severine Mazaud-Guittot, a researcher at the National Institute for Health and Medical Research in France.

For the study, published in the journal Human Reproduction, the team exposed a part of the tissue from each of the 185 human foetuses between 7-12 weeks of development to Ibuprofen and kept the second part as the control. They found that Ibuprofen crosses the placental barrier, with the foetus exposed to the same concentration of the drug as the mother.

Conversely, the tissue exposed to the drug for a week had approximately half the number of ovarian germ cells. The researchers observed significant effects after seven days of exposure to the drug, with cell death seen as early as two days after treatment.

"This is the first study to look at the effects of Ibuprofen on the ovarian tissue of baby girls, and the first to show that it can cross the placental barrier during the first trimester of pregnancy, exposing the foetus to the drug," Mazaud-Guittot said. Just as with any drug, Ibuprofen use should be restricted to the shortest duration and at the lowest dose necessary to achieve pain or fever relief, especially during pregnancy, the researchers suggested.