Controlled Ovarian Stimulation

Controlled Ovarian Stimulation (COS)

Controlled ovarian stimulation (COS) is a form of assisted reproductive technology used to stimulate the ovaries to produce multiple oocytes (eggs) in order to increase the chances of pregnancy. It is used in conjunction with in vitro fertilization (IVF) or other forms of assisted reproductive technology.

The goals of COS are to:

  • Increase the number of eggs that are produced
  • Stimulate the release of more than one egg
  • Reduce the risk of high order multiple pregnancies, like triplets or quadruplets

The process of COS begins with a cycle of contraceptive drugs which help to prevent the ovaries from producing eggs prematurely. This preparatory step is followed by an injection of follicle-stimulating hormone (FSH), which stimulates several follicles in the ovaries to begin maturing. As the follicles mature, they produce more and more estrogen, which allows the doctor to monitor the progress and administer more FSH if necessary.

If the follicles reach the desired size and hormone levels, a second hormone, human chorionic gonadotropin (hCG), is Administered 39 to 40 hours before the eggs are retrieved. This hormone triggers the final maturation of the eggs and their release from the follicles. The eggs are then retrieved through a surgical procedure under ultrasound guidance and frozen for use in IVF or other assisted reproductive technologies.

COS is often used in combination with other assisted reproductive technologies, such as intrauterine insemination (IUI) or in vitro fertilization (IVF). It can also be used in the treatment of infertility caused by hormonal imbalances or ovulatory disorders. COS is not without risks, however, and should be discussed with a doctor before attempting.