There are several types of pills available and most contain a combination of synthetic estrogen-like and progesterone-like substances. These substances prevent the rise in luteinizing hormone, which leads to ovulation. Also, oral contraceptives thicken and chemically alter the cervical mucus, making the uterine endometrium less receptive to sperm.
Possible side effects of oral contraceptives during the initial therapy include nausea, vomiting, fluid retention, headaches and dizziness. Oral contraceptives may also be associated with an increase in blood pressure and an increased risk of thromboembolic disorders (development of clot-like vein occlusions, which can lead to an emboli).
Fitness and Diving Issue
It has been suggested that oral contraceptives may increase a diver’s susceptibly to DCS because of the hormonal changes, which may reduce venous tone and increase water retention. This could affect circulation and theoretically cause the blood to “sludge”, which may interfere with the elimination of nitrogen from the body. To date, no research has found evidence to support this belief.
In fact, unless oral contraceptives pose a clinical problem for women, there is no data to show that their use during recreational scuba diving is a contraindication.
But what about contraception -- are there any specific hazards attached to contraceptive methodologies which women and their consorts should consider. Current thinking is that oral contraceptives do not impose any increased risks on women divers. Most oral contraceptives used in the USA carry a 3-4 fold increase risk of spontaneous non fatal thrombotic events, while pills containing desogestre (and gestodene, a progestin commonly used in pills in the UK and other European countries but not in the US) may carry a 6-8 fold increase in risk compared to no pill use. When considering this increased risk of thrombosis, hyperbaric researchers have been speculated that OC use might increase the likelihood of developing DCS or exacerbate the extent or severity of tissue injury by promoting more rapid and profound activation of the clotting cascade after a gas accident. No animal studies have been done which support this hypothesis. On the contrary one experiment of DCS was done with pigs wherein half of the pigs were premedicated with oral contraceptives and then subjected to chamber profiles inducing DCS injuries. The study found that extent of injuries was identical in the treated and control pigs. No human epidemiologic surveys of sufficient sample size to offer any information that is clinically useful have ever been done.
Recently the gynecologic literature has suggested that 50 percent of thromboembolic on OC may be due to interactions of the medication with inherited clotting disorders, the most common abnormality being a protein substitution in the chain of molecules forming clotting factor V. This substitution renders factor V resistant to cleavage by activated protein C which would inactivate its pro thrombotic action. The resultant disorder is called activated protein C resistance. Underlying coagulation defects have been implicated as increasing the risk of DCS. As a matter of fact, heritable clotting disorders have been implicated in idiopathic aseptic necrosis of the femoral head and a host of other vascular complications. Those populations with a high incidence of factor V Leiden mutation, the most common genotype responsible for this coagulation defect, should be alert to and aware of clotting disorders. Think of them when you encounter the unexpected, undeserved “hit” that just seems too severe for the dive profiles when reviewing the diver’s log and history. And, of course, ask about oral contraceptive use.