Benefits, side effects & risks
Benefits
Many women will often have reduced bleeding or even amenorrhea over time. In fact, NICE include POI contraception as a tool for tackling menorrhagia. It has also been shown to help with dysmenorrhoea and symptoms of endometriosis. It does not increase a woman’s chance of ovarian or endometrial cancer; there is weak evidence to suggest it may even be protective. Unlike many of the other hormonal contraception choices, enzyme inducing drugs do not interfere with POI metabolism so is a good option for women taking these (see Box 3). It is also a good option for women with sickle cell disease and some evidence suggests it may reduce the severity of sickle cell crisis pain.
Risks
POI contraception appears to reduce circulating estradiol and estrone levels. It is postulated that this may be the mechanism for loss of bone mineral density seen in several trials of women on POI contraception. The loss seems greatest within the first year and probably decelerates over time, reverting back to baseline values after cessation. Despite this loss in BMD, there is no compelling evidence to suggest there is an increase rate of fractures with POI use. With this in mind, caution should be used when prescribing POI to women at greatest risk of bone mineral density loss (teenagers, perimenopausal women, and those with risk factors for osteoporosis).
POI contraception use may marginally increase the risk of developing breast cancer and cervical cancer, though data suggesting this is limited. The risk of breast cancer appears to drop back to baseline after 5 years of stopping POI.
Overall, progestrogen-only contraceptives do not appear to increase the risk of venous thromboembolism. However, studies have shown POI use slightly increases the risk. For this reason, FSRH give it a UKMEC 2 criteria for women with a history of VTE or genetic tendency (UKMEC 3 for antiphospholipid syndrome/SLE as higher risk).
POI appears to alter lipid metabolism in early use, reducing HDL levels. This appears to even out after 2 years of use. Although there is little statistically significant evidence of increased MI/strokes with POI use, for women with a previous history of MI and stroke, POI is UKMEC3.
Side effects
POI often alters a woman’s menstrual cycle. While some women will have lightened bleeding or amenorrhea, others will have irregular bleeding or prolonged periods, with a trend towards less bleeding with continued use. A study of women on POI found while 10% on Depo-Provera had amenorrhea/light spotting at 3 months, nearly 50% were free of periods after a year. With this in mind, women should be advised about changes in bleeding patterns before starting POI, as altered bleeding is a common reason for stopping POI.
POI is associated with weight gain. This is most prominent in young women (under 18 years old), especially those already markedly overweight prior to starting POI contraception. Women who gain over 5% of their baseline body weight in the first 6 months of POI are more likely to continue to put on weight if POI is continued.
Other possible reported side effects include localised skin reactions, headache (around 10%), acne, hair loss (SPC state 1-10%), decreased libido, labile mood (though not depression), hot flushes and vaginitis.
POI use is associated with a significant delay in fertility after cessation. The affect is widely variable but can be over a year and women should be advised of this before starting POI.
