Some unexplained miscarriages could be caused by a surge in oxygen levels around the third month of pregnancy. Researchers at University College London and Cambridge University have discovered that during this time, the level of oxygen in the placenta increases threefold. Combined with other factors, this sudden change may be enough to cause a miscarriage, says team member Dr Graham Burton. The findings were presented at the European Society of Human Reproduction and Embryology annual meeting in Bologna, and reported in New Scientist last week.
The scientists placed tiny monitors in the placentas of 30 women, and found that the amount of oxygen reaching the developing fetus shoots up between the 8th and 15th weeks of pregnancy. 'This clearly shows there are two distinct phases in pregnancy', said Burton. Most embryologists previously believed that oxygen levels rise gently throughout pregnancy.
Dr Eric Jauniaux, of University College, said that taking antioxidant vitamins in early pregnancy to 'mop up' free radicals (harmful chemical by-products formed by oxygen) could help protect the fetus. Obstetrician Lesley Regan, of Imperial College London, agrees there should now be trials involving antioxidants, but warns: 'There's no information in the literature to indicate that vitamins C and E [antioxidant vitamins] are safe in pregnancy.'