The new method would save time and money of thousands of infertile couples and help them decide whether investing in IVF procedure would yield any results for them.
The study, published Tuesday in the Public Library of Science journal, identifies four most powerful factors that indicate with 70 percent accuracy the chances of pregnancy after a single round of in vitro fertilization.
In vitro fertilization, in which a woman's eggs are removed and fertilized in the laboratory, is an expensive procedure and does not guarantee pregnancy.
The researchers examined 665 cycles of in vitro fertilization in women under age 45. Some 4,144 embryos were created. Typically, each IVF cycle produces five to 12 embryos.
Stanford researchers isolated the four factors out of 30 to better predict pregnancy outcomes. They are the total number of embryos that a couple produces during a cycle, the number of embryos that survive to the eight-cell stage, the percentage of embryos that stop dividing and a woman's level of the follicle-stimulating hormone. This hormone estimates how well the ovaries are working.
According to the Society for Assisted Reproductive Technology, anywhere from 18 to 45 percent of IVF treatments on women using their own eggs result in pregnancy. The researchers are now focusing to develop tests that predict the likelihood of pregnancy before fertility treatments begin.
While the overall live birth rate via IVF in the U.S. is about 27 percent per cycle (33 percent pregnancy rate), the chances of a successful pregnancy via IVF vary widely based on the age of the woman (or, more precisely, on the age of the eggs involved).
Where the woman's own eggs are used as opposed to those of a donor, for women under 35, the pregnancy rate is commonly approximately 43 percent per cycle (36.5 percent live birth), while for women over 40, the rate falls drastically - to only 4 percent for women over 42.
