Conception is a special moment, when sperm merges with an egg to create a new life. Now researchers have discovered that this moment is accompanied by a flash of light, which could signal the viability of an embryo for in vitro fertilization (IVF) treatments.
The discovery comes from Teresa Woodruff, professor of obstetrics and gynecology, along with other researchers at at Northwestern University in Chicago, Illinois. They published their findings in the journal Nature Scientific Reports on April 26th.
Researchers already knew that when mouse eggs are fertilized, the amount of calcium increases and zinc is released rapidly, helping to regulate embryo growth. This released zinc then binds to other molecules and creates a small flash of light, visible through a microscope. However, in the current study, the researchers set out to discover if the same spark happens with human conception.
Because there are legal limitations surrounding research with human embryos, the researchers isolated an enzyme present in sperm instead of using an actual sperm to fertilize an egg. When they injected this enzyme into a human egg, it activated the egg just as a sperm would. This triggered the increase in calcium and release of zinc, causing the same microscopic spark of light other researchers had observed in animals. The researchers even released a video showing this spark of light at human conception.
The research may accomplish more than just sparking wonder at the “fireworks” surrounding the moment of conception. The researchers say that this discovery could have implications for IVF treatments.
IVF treatments can be a labor-intensive, and expensive, process. The treatments involve fertilizing one or more eggs in a laboratory, creating so-called test-tube babies, then implanting that embryo or embryos into the womb. The problem is, before doctors implant the embryo, it is difficult to tell how viable the embryo is, that is, what chance it has to continue growing for a successful pregnancy. This means doctors will often implant multiple embryos at the same time, increasing the chance that one of them will thrive but also increasing the chance of multiple births, which can be medically risky.
According to the researchers in the current study, this zinc spark could signal the viability of the embryo. In the previous animal studies, researchers have found a link between the intensity of the zinc spark and the quality of the egg. If someone could discover a way to measure the intensity of the zinc spark when human eggs are triggered by sperm enzymes, technicians could use this signal to determine the quality of the egg for IVF treatments. This could allow them to select only the highest quality egg for fertilization and implantation into the womb.
The first successful IVF treatment dates back to 1978 in England, then the procedure was introduced into the United States in 1981. Because of its complexity and high price tag, only about five percent of couples with infertility choose this treatment, but the procedure has resulted in about 200,000 births in the U.S.
Causes of infertility can include ovulation problems in women, medical conditions like endometriosis in women, and in men, low sperm counts and inability of sperm to survive in the woman’s body. Usually doctors will treat infertility with drugs or hormonal injections first, since they are much less expensive than IVF treatments. However, when other measures have failed, couples may turn to IVF treatments. With the high cost of each implantation procedure, some couples opt to implant multiple embryos, hoping at least one will be successful. However, this could mean that multiple embryos survive, producing twins, triplets, and more. Although twins can be appealing to parents, twins can mean complications for the mother and the babies, who may be born premature and with health issues. Having better, non-invasive methods at their disposal to choose the best embryo could help doctors increase the chance of a successful pregnancy, without the risking a multiple birth.