Obesity and contraception

Obesity is defined by the WHO as “a body fat of greater than 35 % in women calculated using dual energy X-ray absorptiometry (DEXA). According to WHO, currently 20-30% of adults in Europe are clinically obese and prevalence of obesity had doubled in less than 20 years.

As prevalence increases it’s important to determine if obesity is a risk factor for pregnancy. It is known that extremes in weight can effect fertility. Obesity is associated with ovulatory dysfunction, a decreased rate of spontaneous pregnancy and a decreased response to fertility treatment.  However despite this, more than 20% of pregnancies in the United Kingdom and other developed countries take place in obese women.

As an important part of obesity, the metabolic syndrome involves numerous metabolic abnormalities that increase the risk of cardiovascular disease and diabetes. It is well documented that pregnancy in obese women often leads to several morbidities.

As a result, it’s important to look at the link between oral contraceptive pills and body weight. To date literature does not suggest that contraceptive pills increase body weight. It is known that most adult’s gain weight over time. Pregnancy is also associated with weight gain. For obese women going though pregnancy, the weight is often retained post-partum.

Are contraceptive efficacious in obese women?

The majority of data shows that there is not a decreased efficacy of contraceptives in obese women with the exception of the transdermal combined contraceptive patch that is less effective in a woman with a body weight of more than 90kg. Pharmacokinetics studies with COC and CVR found reduced ethinylestradiol levels, but no decreased progestin levels in obese women. This didn’t result in decreased ovarian suppression as the progestin is the most relevant for contraceptive efficacy, but as achieving steady state of progestin levels is delayed, it may be beneficial to provide obese women additional protection for the first 14 days.

Are COC pills safe in obese women?

As we’ve heard throughout the conference the biggest concern for use of an estrogen containing treatment is the increased risk of VTE. Obesity doubles the risk of VTE so when combined with COC has a large impact on potential risk. However the combined risk of obesity and pregnancy far exceeds the risk of obesity and COC use. As COC does further increase the risk of VTE and ATE in obese women it should only be used if no other acceptable contraceptive methods are available to the patient.

Obese women are also more likely to have comorbidities such as HTA, hyperlipidaemia, diabetes or high risk of CCV diseases that also increase risk of MI and stroke.

Are there benefits of using COC in obese women?

Obese women have a higher risk of endometrial cancer and may benefit from the decreased risk of endometrial hyperplasia and endometrial cancer associated with COC use.

What about using POC in obese women?

At present no data indicates decreased efficacy of POP in obese women, considering this does not increase VTE and ATE risk in obese women, it is an important and safe option.

Using contraception to prevent unwanted pregnancies is recommended to all women regardless of their weight. POC and IUD have minimal metabolic effect and are effective in obese women so should be tried over use of COC which should only be used if other methods are not acceptable due to its increased risk of VTE and ATE.