In a study in mice and human cells, Johns Hopkins Medicine researchers say that they have developed a tiny, yet effective method for preventing premature birth. The vaginally-delivered treatment contains nanosized (billionth of a meter) particles of drugs that easily penetrate the vaginal wall to reach the uterine muscles and prevent them from contracting. If proven effective in humans, the treatment could be one of the only clinical options available to prevent preterm labor. The FDA has recommended removing Makena (17-hydroxyprogesterone caproate), the only approved medicine for this purpose, from the market.