HomeHealth articleslevonorgestrelWhat Is the Role of Levonorgestrel for Emergency Contraception in Obese Individuals?

Levonorgestrel for Emergency Contraception in Obese Individuals - An Overview

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Levonorgestrel is used for emergency contraception in case of unprotected sex. The article describes its role in obese individuals in detail.

Medically reviewed by

Dr. Vrinda Khemani

Published At March 15, 2023
Reviewed AtApril 6, 2023


Emergency contraception, also called postcoital contraception, is a means of contraception used to prevent pregnancy as a result of unprotected sexual intercourse. Emergency contraception is required if no protection was used during sex, failure of the contraceptive, for example, bursting or tearing of the condom, or missed doses of oral contraceptive pills. Oral emergency contraception first came into the limelight in the 1960s. The Food and Drug Administration (FDA) approved the first product for emergency contraception in 1998. Since then, a variety of new products have been introduced.

Emergency contraception comprises the following four types:

  • A Progestin-only pill containing Levonorgestrel.

  • A pill containing Ulipristal acetate (UPA).

  • Copper intrauterine device (IUD).

  • A combination of certain birth control pills like Estrogen-Progestin.

Obesity is a predictable risk factor for the failure of Levonorgestrel as emergency contraception, which is a significant problem. Unfortunately, few studies have been conducted to evaluate the relationship between oral emergency contraceptives such as Levonorgestrel and increased weight.

What Is Levonorgestrel?

Levonorgestrel belongs to a class of medications known as progestins. These drugs prevent the release of an egg from the ovary, thereby blocking the fertilization process. It also changes the uteral lining to prevent the development of pregnancy. Levonorgestrel helps in pregnancy prevention but does not prevent the transmission of the human immunodeficiency virus (HIV), which causes (AIDS) acquired immunodeficiency syndrome and other sexually transmitted diseases.

Levonorgestrel is used to prevent the development of pregnancy after unprotected sex, such as intercourse, carried out without the use of any birth control measures or with a failed birth control measure, such as a slipped or torn condom or birth control pills not taken as planned. Therefore, regular intake of Levonorgestrel to prevent pregnancy and as a birth control measure is not advisable. This emergency contraceptive pill is used when regular birth control measures fail or are misused.

How Does Emergency Contraception Work?

During the process of ovulation, there is an increase in the luteinizing hormone levels in the bloodstream, which triggers an egg release from the ovary (ovulation). The emergency contraceptive can be used till five days after having unprotected sex but works best if taken as soon as possible after indulging in unprotected sex. Emergency contraception with the help of pills works by delaying ovulation, the monthly release of an egg during the menstrual cycle. It might also prevent the fertilization of the egg with the sperm if ovulation has occurred already. Still, it is ineffective if fertilization and egg implantation has already occurred.

Emergency Contraception With Levonorgestrel in Obese Individuals:

Levonorgestrel (LNG) is an oral man-made progestogen that was developed in the 1970s and is an active substance of emergency contraception measure. It is thought that there might be a loss of efficiency of Levonorgestrel associated with high body mass index (BMI) or body weight. BMI and weight are two different things. Body mass index or BMI is determined by dividing an individual's weight by the square of their height. A high BMI and body weight make Levonorgestrel inefficient as an emergency contraceptive. Certain studies have shown that obese women have a high risk of pregnancy using emergency contraception containing Levonorgestrel at the standard dose compared to women with average weight. In addition, doubling the dose does not improve the inhibition of ovulation among women with obesity.

Several studies show that Levonorgestrel loses potency in women who weigh about 75 kg and does not work at all in women weighing 80 kg or more. Levonorgestrel prevents about half of the pregnancies that would have occurred without intervention, but the effectiveness changed drastically when weight was factored in. When given in women with a BMI (body mass index) of 25 or higher, Levonorgestrel does not work effectively and stops working completely in women with a body mass index of 30 or higher. The risk of developing pregnancy in obese women who took Levonorgestrel is slightly more as compared to women who do not take the contraceptive pill.

Levonorgestrel works as an emergency contraceptive by preventing the LH surge (the increase in the levels of the luteinizing hormone) by blocking the rupture of the follicle. Studies have shown that compared to women with normal BMIs, those with higher BMIs have reduced concentrations of the drug in the plasma. Successful implementation of emergency contraception depends on reaching an inhibitory concentration before the beginning of the luteinizing hormone surge. Thus a significant reduction in the levels of Levonorgestrel could influence its efficiency.

The amount of free or unbound drug is pharmacologically relevant. For drugs like Levonorgestrel, the amount of the drug that is bound to the sex-hormone binding protein is considered biologically active. Levonorgestrel is bound to the sex hormone-binding protein. Thus some researchers thought that the sex-hormone binding property of Levonorgestrel is a more critical component than the plasma concentrations of the drug. In addition, the sex-hormone binding protein levels are lower in obese individuals with a high BMI.


Emergency contraception provides an additional defense against unintended pregnancy after indulging in unprotected intercourse. Oral emergency contraceptives such as Levonorgestrel (LNG) act by inhibiting or delaying ovulation and reducing the risk of pregnancy by up to 90 percent. Emergency contraception containing Levonorgestrel is widely available in many countries over-the-counter without a prescription. Levonorgestrel is very effective in women with a body mass index of less than 25, as compared to individuals with a body mass index of greater than 30.

There are quite a few theories suggesting why Levonorgestrel fails in obese women. the dilution of the drug in a larger blood volume; hormones becoming segregated in the fat cells; or the different metabolism of the drug in an obese person, but nothing is definitive since there are not many studies that have thoroughly evaluated the relationship of the effectiveness of Levonorgestrel in obese women. It could be possible that a larger individual requires a larger dose of the drug. In a nutshell, individuals with a high BMI and weight potentially have an increased risk of failure of emergency contraception with Levonorgestrel. However, doubling the dose of the drug does not seem to be effective in attaining contraception.

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Dr. Vrinda Khemani
Dr. Vrinda Khemani

Obstetrics and Gynecology


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