Hormonal Contraception in Obese Women - An Overview

Introduction

Obesity is a lifestyle disorder involving excessive body fat. It occurs when the body mass index (BMI; weight to height ratio) is more than 30. According to the National Family Health Survey 2015, obesity is rising in India, especially among women. Further, obese women belong to more affluent families. Contraception is pregnancy prevention. The use of hormonal contraceptives can affect obese women. Likewise, obesity can also affect hormonal contraceptives’ potency.

What Is the Impact of Obesity on Fertility?

Obesity can be present with or without hormonal disturbances in a woman. It can lead to irregular menstruation due to a reduced ovulation frequency. Normal ovary function is disturbed in an obese woman. Studies also show a higher level of male sex hormones (androgens) in obese females.

What Are the Common Hormonal Contraception Methods?

Hormonal contraception is a birth control method. It consists of steroid hormones, namely, estrogen or progestin (progesterone). The most common hormonal contraceptives are oral pills with both estrogen and progestin. It is also called combined oral contraceptives (COCs). Others are progestin-only contraceptive pills, contraceptive vaginal rings (CVR), transdermal patches, depot-medroxyprogesterone acetate (DMPA) injections, intrauterine hormonal devices, and contraceptive implants. The morning-after pill (emergency pill) is also another hormonal contraceptive.

What Is the Efficacy of Hormonal Contraception in Obese Women?

The efficacy of hormonal contraception may be related to increased body fat. Studies have revealed that obesity may be a potential risk factor for oral contraception failure. Some researchers claim that OCs are less effective in obese women than others. Various proposed mechanisms are:

1. The OCs are diluted in the larger blood volume of obese women. The hypothalamus and pituitary gland release hormones for ovulation via the hypothalamus-pituitary axis (HPA). OCs prevent this action. However, in obese women, inadequate HPA suppression can occur.

2. Basal metabolic rate (BMR) is the energy needed to perform essential metabolic functions. Obese women have an increased BMR than their counterparts. Also, there is an alteration of steroid metabolism due to an increased BMR.

3. Increased liver enzyme metabolism is noted in obese women. This further results in altered hormonal levels.

4. Another mechanism is the increased drug deposition in the fat mass.

Levonorgestrel (LNG) and Ethinyl estradiol (EE) are the two most common synthetic estrogens in OCs. The clearance of LNG and EE is altered in obese women. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) work in coordination for ovum production (released by the pituitary gland). Obese women have higher levels of FSH and LH due to the altered clearance of OCs, resulting in increased chances of ovulation. It also may take longer for OCs to reach a steady concentration. Hence, obese women may need a backup method for pregnancy prevention.

How Safe Is Hormonal Contraception in Obese Women?

There is a controversy regarding the safe use of hormonal contraception in obese women. The usual side effects are headache, acne, mood changes, nausea, and vomiting. However, a severe adverse effect is the increased risk of venous thrombosis (clot formation) and thromboembolism (TE, which occurs when the blood clot obstructs blood circulation). OCs increase the risk, especially during the first year of use. Deep vein thrombosis (DVT) and pulmonary (lung) embolism (PE) are examples of these conditions. The risk of DVT and PE is double in obese women compared to non-obese women of the same reproductive age. The underlying mechanism may be an increased tendency towards coagulation (clotting) and inflammation. C-reactive protein is an inflammatory marker involved in obesity and TE pathways. Hence, it may associate with the two conditions. Obese women using hormonal contraceptives are also at a higher risk of cardiovascular disease.

What Are the Recommendations for the Use of Hormonal Contraception in Obese Women?

The factors to note before prescribing OCs in obese women are:

1. Family History: A positive family history of TE is a significant risk factor.

2. Age: An age of greater than 35 years is to be kept in mind.

3. Smoking: Cigarette smoking is an independent risk factor for TE and leads to increased hospital admissions.

Age greater than 35 years, smoking, OCs, and obesity are some combinational risk factors for TE precipitation. The recommendations for different hormonal contraceptives in obese women are given below.

1. Progestin-Only Pill (POP): POP is a safer alternative to COC in obese women. It is because COC poses a greater risk of thrombosis and cardiovascular disease. It has slightly lower efficacy than COC. Hence, obese women should be more attentive while taking POP.

2. Contraceptive Vaginal Ring (CVR): A CVR is inserted into the vagina for three weeks and removed for one week. The CVR has lower EE as compared to COCs. However, the exposure to contraception is stable and precise. In CVR, contraception is not affected by body weight. Also, an obese woman experiences fewer side effects.

3. Transdermal Patches: Transdermal patches are applied on the body for three weeks and removed for one week. Studies show the patch is ineffective in women of more than 90 kilograms. Hence, a transdermal patch may not be the first choice for obese women.

4. Depot-Medroxyprogesterone Acetate Injections (DMPA): DMPA injections are given into the muscle (intramuscular) or under the skin (subcutaneous) every three months. The efficacy of DMPA injections in obese women is comparable to that in non-obese women. Rarely a severe thromboembolic event or cardiovascular disease has been reported. However, a significant side effect of DMPA injections is decreased bone mineral density (BMD). Further, patients also report weight gain. Hence, for obese women, weight gain may be a factor in choosing DMPA.

5. Intrauterine Devices (IUDs): IUDs release LNG. These are suitable for obese women as estrogen-related side effects and weight gain are avoided. Hormonal IUDs may be the choice of hormonal contraception among obese women. But, the difficulty arises in determining the position and size of the uterus during IUD insertion.

6. Implants: The implantable hormonal contraceptive has a rod containing Etonogestrel, a third-generation progestin. It releases the hormone slowly over three years after insertion under the arm skin.

An important point regarding weight-loss (bariatric) surgery is that women should avoid conception during weight loss as the efficacy of OCs may be altered post-surgery. Also, obese women should choose other methods of contraception.

Conclusion

Hormonal contraception in obese women can be effectively achieved. However, continuous monitoring after regular intervals is essential. Practitioners should also provide appropriate health counseling regarding exercise and nutrition to obese women during hormonal contraceptive use.