In women seeking to become mothers, dong quai may enhance fertility by stabilizing estrogen levels. Estrogen levels rise during the first half of a woman's period, peaking a day or two before ovulation. If estrogen levels don't start to go back down by the day of ovulation, uterine tissues may become too "swollen" to accommodate the fertilized egg or eggs. Stabilizing the female partner's estrogen levels makes it easier for the fertilized egg to "take hold" in the lining of the uterus.
And dong quai may be helpful for men seeking to become fathers, too. It's not unusual for men to have a normal sperm count but a problem with sperm that cannot "swim." The mucus lining the cervix captures most ejaculated sperm, and only the very strongest make a trip further into the uterus. "Swimming" to fertilize the egg takes a lot of energy, and burning energy creates free radicals. The sperm, for which fertilization is a life or death issue, uses all its energy to try to be the first to reach the egg. This process can generate so many free radicals that the sperm's "tail" is damaged and it cannot continue its journey. And sometimes not even a single sperm reaches the egg.
Dong quai supplies an important antioxidant, ferulic acid. This compound reduces damage to the sperm cell as it burns energy to fulfill its purpose. Men who take dong quai may have stronger sperm and are somewhat more likely to become fathers. There is one major downside to using dong quai. Its use is not recommended for anyone who has herpes. Herpes infections are not active all the time. The same free radical reactions that power the sperm to swim, however, also power cells to become inflamed during a herpes outbreak. Since taking dong quai can make an outbreak worse, no one who has herpes should ever take it. Dong quai is also not recommended by men who have had chemotherapy with the drug Bleomycin. And, since it can stimulate menstrual flow, it should never be taken by women once they become pregnant.