Polyspermy occurs when more than one sperm fertilizes an egg, often resulting in the death of the embryo. This happens when there is an error during cell division, known as Meiosis and Meiosis II, as chromosomes are shuffled and recombined to produce a different genetic combination for four genetically unique haploid cells (the number of chromosomes in a gamete of an individual).
Although most don’t make it past implantation, the embryos that do survive multiple sperm fertilization can sometimes survive up to 15-16 weeks of pregnancy, with a small number surviving right up to the third trimester or to full term. Unfortunately, those that make it to full term die shortly after birth.
The body has several defense systems in place to prevent this from happening. The oviduct, also known as the fallopian tube, is a crucial aspect of reproduction. Not only used for the fertilization of the egg, it regulates the amount of sperm that reach the egg and also serves as a sperm reservoir. Sperm attach to and are retained in the isthmus (which lies in the wall of the uterus), and only a select few will move on to the ampulla for fertilization. Incapacitated sperm will bind in order to prevent Polyspermy.
Normally, there is a “block” that occurs after insemination, known as the slow block or egg coat block, which hardens the egg between 30 and 60 minutes after fertilization. Women who experience Polyspermy usually conceive later on during their ovulation cycle, and their eggs usually have a more difficult time establishing the membrane block.
Any questions regarding Polyspermy and treatment should be directed to your doctor or medical professional.