Ovarian hyperstimulation syndrome

 

Women participating in fertility treatment are often required to undergo ovulation induction.

Ovulation induction involves the use of drugs which are designed to mimic, to a large extent the production of natural female hormones.

Gonadotrophins are secreted by the pituitary gland of a female and the functional relationship of the gonadotrophic hormones is complicated. In a normal menstrual cycle, Follicle Stimulating Hormone (FSH) stimulates the development and maturation of the follicles and ova. As the follicle develops, it produces oestrogen in increasing amounts which, at mid-cycle, stimulate the release of Luteinising Hormone (LH). This causes the rupture of the follicle with ovulation and converts the empty follicle into a corpus luteum which secretes progesterone.

Chorionic gonadotrophins are produced by the placenta and have predominantly luteinizing properties. There are other gonadotrophins which predominantly have follicle stimulating properties.

Drugs containing gonadotrophins, which themselves have been obtained from postmenopausal women or produced by genetic engineering, are commonly used in fertility treatment when ovulation induction is required.

Ovulation induction in connection with assisted conception techniques, is a procedure carried out by specialist centres dealing with infertility problems, whether as part of the National Health Service or at a private hospital or clinic. The manufacturers of the drugs commonly used in ovulation induction produce, and distribute, guidelines for the use of the drugs to all such hospitals and clinics. It is, therefore, the responsibility of the individual doctor or consultant to ensure he or she is fully aware of the way in which the gonadotrophin drugs work and their possible side effects.

One recognised side effect of gonadotropins is ovarian hyperstimuation syndrome, the severity of which varies between mild, moderate and severe. In a normal menstrual cycle, one egg is produced each month from one or other of a female’s ovaries. Ovulation induction involves the use of higher levels of gonadotrophins, the desired effect being to produce more than one egg for use in connection with assisted conception techniques.

Ovarian Hyperstimuation Syndrome (OHSS) is, therefore, not an altogether uncommon side effect of the use of gonadotrophins. Mild OHSS results in some ovarian enlargement with slight abdominal pain and swelling and the treatment for mild OHSS is pain relief. Moderate OHSS results in more noticeable pain and swelling with nausea and vomiting. Again, pain relief will be required and the treatment also includes bed rest. Severe OHSS can result in the leakage of hormones and fluid from the ovaries and this in turn may cause an accumulation of fluid both in the abdominal cavity and in the chest. Active medical and/or surgical intervention is always required in cases of severe OHSS. OHSS generally does not occur until between 3 and 6 days after ovulation and, ironically, can be heightened by a pregnancy occuring, the levels of natural human chorionic gonadotrophins increasing as a result of the pregnancy.

The incidence of mild and moderate forms of OHSS has been reported to be between 10 and 20% of all females undergoing ovulation induction treatment and the use of gonadotrophins. Severe forms of OHSS occur in less than 1% of patients undergoing ovulation induction. Untreated, severe OHSS can result in a patients death. It is believed that published literature records only 3 fatalities since the commencement of the use of gonadotrophins approximately 30 years ago. It has been estimated that in the UK alone 40,000 ovulation induction cycles were carried out in 1993 using gonadotrophins, further estimate that worldwide, there are likely to be between 400,000 to 500,000 ovulation induction cycles carried out each year.

Any treatment which can induce side effects is obviously going to be of concern to those undergoing or considering such treatment. As the level of drug used and possible reaction is very individual, it is recommended that females undergoing ovulation induction treatment with the use of gonadotrophins should be carefully monitored through the procedure. Most hospitals and clinics will be able to offer monitoring in the form of regular ultra sound scans together with the analysis of urinary or blood oestrogen excretions. Most clinics and hospitals will also be able to produce a factsheet which should give more details and information to the patient as regards the side effects of treatment and the action to be taken if all or any of the side effect occur. Basically, although OHSS is a recognised condition, the use of patient information sheets and the careful monitoring of patients should minimise the risk of the condition becoming severe. If a woman is perceived to be at risk of developing OHSS as a result of producing too many follicles in ovulation induction treatment, the cycle is usually stopped so that ovulation does not occur. In IVF cycles, egg collection takes place but rather than embryos being put into the uterus they are frozen where possible.

Clearly, the medical profession generally and the drug companies specifically do not wish to expose any patient to discomfort or more serious consequences as a result of any treatment where this can be avoided, and, therefore, as part of the natural development of medical science, techniques and procedures are constantly being reappraised and monitored.

Provided diagnostic procedures are carried out with care all risks to patients which may possibly involve OHSS should be minimised wherever possible.