When it comes to fertility, the ability for a sperm to move quickly to the right location is very important, and very difficult. To reach a fertile egg, sperm must swim a distance proportionate to a human swimming half the length of the Gulf of Mexico, while dealing with obstacles like cervical mucus condition, competition by other sperm, and ovulation timing that may not be within the week-long lifetime of the sperm. It is a journey with many risks but only one reward. Recent studies have shown that one motivator for sperm to increase their motion, and therefore their speed, is exposure to more feminine scents. These studies may be the key to encouraging sperm motility and therefore boost fertility chances.

The Studies
It has been known for years that female vaginal fluids are attractive to sperm. However, it was only recently that a scent receptor, called hOR17-4, was discovered. This has allowed for targeted studies that bind different scent molecules to the receptor. A 2003 joint study between US and German researchers first discovered two substances, which they named bourgeonal and undecanal. Sperm were shown to move toward high concentrations of bourgeonal and away from undecanal. Bourgeonal is shown to have a pleasant, floral scent similar to lily of the valley.

In 2013, another study took this information even further and began narrowing down some of the scents that are found to be present within typical female vaginal fluids. The scents smelled like a variety of things, like bell pepper, caramel, urine, vanilla, sulfur, and flowers. The urine and caramel scented ones, when they came in contact with the scent receptors, caused a chain reaction within the sperm to get it to release calcium molecules. This encouraged it to whip its tail faster, guiding it in a certain direction. This suggests that the scents can be used by a sperm as a sort of map to get to the right location in order to fertilize the waiting egg. However, the successful effect of the chemicals on a sperm’s motility can only be received when they are at sufficiently high concentrations.

The Implications
The studies suggest two important things. First, these receptors exist on a sperm molecule to help it to find its way. Second, this understanding can have some potential implications in fertility medicine to help in cases of difficult conception. Fertility specialist Dr. Parviz Kavoussi suggests that one area in which this study can help sperm is in a case where a woman has scar tissue. This tissue may be an obstacle for sperm motility, or the lack of normally functioning cells within this section of uterus or cervix may mean that the sperm loses the scent trail as they cross this area, and essentially get lost. The answers to these questions are still hypothetical, and would need to be the subject of future studies.

As more studies are conducted, Dr. Kavoussi and others predict that there are likely a number of other chemoattractants, as they are called, to be discovered. Each new chemical may provide the key to furthering the science of fertility medicine and helping sperm with low motility overcome the obstacles needed to result in successful, healthy pregnancies.