Seminal plasma is the fluid portion of semen that surrounds and carries sperm. It is produced mainly by the seminal vesicles and prostate gland and contains proteins, cytokines, prostaglandins, growth factors, and other signaling molecules that help support sperm and communicate with the female reproductive tract.
Researchers have proposed that seminal plasma may also play a role in implantation by:
- Promoting maternal immune tolerance to the embryo.
- Recruiting immune cells to the uterus.
- Increasing endometrial receptivity.
- Stimulating the formation of new blood vessels (angiogenesis) that may support implantation.
During IVF and ICSI, sperm are separated from seminal plasma before fertilization, so embryos develop without direct exposure to seminal plasma. Successful IVF pregnancies show that seminal plasma is not required for fertilization or implantation, although researchers continue to study whether exposure before embryo transfer could improve pregnancy outcomes.