Steroid may prevent repeated miscarriages

2019-03-02 05:16:09

By Rowan Hooper A steroid may prevent repeated miscarriages, says a UK researcher who has shown the chemical can reduce the number of “killer cells” accused of causing miscarriages. But other experts say clinical trials to explore this would be too risky, not least because the exact role of these cells is unknown. The controversy revolves around a type of immune cell called a natural killer (NK) cell. Although no one knows what the function of NK cells is, they have been implicated in the implantation of embryos in the womb. However a few small studies suggest that high numbers of NK cells increase the risk of miscarriage. Some private clinics already offer treatments such as steroids and immunosuppressants to reduce the number of NK cells in women who have suffered recurrent miscarriages. But claims of dramatic results, and the publicity given to them, have been attacked by fertility experts who argue that there is no scientific basis to the treatments. “The link between the number of NK cells and their function is hard to make because we don’t know what they do,” says Ashley Moffett of the University of Cambridge. Confusingly, there are two types of NK cells: peripheral NK cells in the blood, and uterine NK cells in the lining of the womb. Some clinics estimate the number of uterine NK cells is based on the number of peripheral NK cells. But Moffett says that is like using the number of black taxis in London’s Trafalgar Square to estimate the number of red taxis on motorways. The latest study addresses this criticism. Siobhan Quenby of the University of Liverpool, UK, took samples from the wombs of 110 women who were not pregnant but had suffered an average of six miscarriages each. In 33 of these women, uterine NK cells accounted for at least 5% of the cells in the sample, while in the other women they accounted for less than 5%. Quenby asked the 33 women to take the steroid prednisolone, which is used to treat conditions such as asthma and eczema. NK cells have steroid receptors on their surface, and some studies suggest that steroids such as prednisolone knock out the receptors. Twenty-nine of the women took 20 milligrams of prednisolone daily for 21 days from the start of their menstrual cycle. By day 21, uterine NK cell numbers had dropped by an average of 6% compared with women not taking the steroid, Quenby told the European Society for Human Reproduction and Embryology meeting in Copenhagen, Denmark, on Monday. The trial was originally going to stop at this point, but all the women demanded to be allowed to continue on the drug when they were told the results. “They were desperate for it,” says Quenby. Six of the women have since become pregnant, with one ending in miscarriage and two in births. The remaining three pregnancies are now beyond the point at which most miscarriages occur. Quenby stresses that the results are preliminary and do not prove that an excess of uterine NK cells cause miscarriages. “We urgently need clinical trials,” she says. But Moffett is not so sure. “Steroids have serious side effects and there may be additional risks to women in early pregnancy,” she says. “We’re not yet ready for clinical trials because we don’t know enough about what NK cells do. It’s too premature to say: ‘right,