Hormonal-Type Contraception - Birth Control Pills

Written by: Lisa Cheng

Hormonal-type Contraception

Hormones regulate the menstrual cycle; therefore many types of contraception target regulation of hormone production. Some women prefer hormonal-type contraception because it does not ‘interfere’ with intercourse and the woman is in control of her health. There are many forms of hormonal-type contraception including oral contraceptives, vaginal rings, and some intrauterine devices. This is not an exhaustive list, but it is the most common and relevant types.

Birth Control Pills

In this article, we will discuss combined oral contraceptives and progestin-only pills. Both types of birth control pills contain synthetic hormones. Oral administration is the most convenient method of drug delivery. In Canada, chronic medications are typically dispensed in three-month periods after the initial one-month trial, adding on to the ease of access.

Combined Oral Contraceptives

Combined oral contraceptives contain a low dose of a progestin (a synthetic form of progesterone) and an estrogen, which act like the naturally produced progesterone and estrogen, respectively. Synthetic hormones can disrupt the menstrual cycle by preventing egg release from the ovary, making fertilization is not possible.

Progesterone is the main contributor to avoiding an unintended pregnancies; that is, consistent progesterone levels will stop the surge in luteinizing hormone secretion, a key factor to ovulation (i.e., no egg release) (1). Furthermore, progesterone changes the cervical mucus (fluid secreted within the cervix) to reduce the sperm’s motility (1). Mucus allows for sperm to continue travelling up the reproductive tract where it may come into contact with the egg. When progesterone levels peak during the menstrual cycle, the cervical mucus thickens or dries up, making it impermeable (2). Therefore, introducing the synthetic progesterone, progestin, into the body will prevent ovulation and constantly makes it more difficult for sperm to penetrate through the cervix. Progesterone also plays a role in thinning of the uterine wall lining resulting in lighter menstruation. In parallel, estrogen (in the forms of estradiol, ethinyl estradiol, or estetrol) prevents development/growth of follicles by suppressing follicle-stimulating hormone, thus suppressing the maturity and release of eggs (1).

How does it work? 

These pills are prescribed as daily intakes at the same time every day to maintain their hormonal levels. Birth control pill packs can come with 21 or 28 pills and there is no significant difference between the two options. The last seven days or pills in the 28-pill pack do not contain hormones (e.g., sugar pills) and this exists to help a woman remember to stay on her regimen. As such, instructions for the 21- and 28-pill pack differ. After taking the last pill in the 21-pill pack, they will wait 7 days before taking a pill from the next pack whereas there is no ‘break’ between the 28-pill packs.

Development of follicles occurs during the 7 days when no hormonal pills because there is a gradual decrease in progestin. Levels of follicle-stimulating and luteinizing hormone, which were previously suppressed, are now increasing with estrogen. Their concentrations indicate to the body that it is time for menstruation. After the 7 days, progestin and estrogen are re-introduced thus not allowing follicle maturation and subsequent ovulation.

Contined Use of Combined Oral Contraceptives

Some women choose extended or continuous use because they are likely to have four or less periods in one year. This effectively reduces the number of headaches, premenstrual symptoms, and heavy bleeding. Extended use of combined oral contraceptives will have women taking hormonal pills for twelve consecutive weeks (or eighty-four days) before having one week of non-hormonal pills. Continuous use of oral contraceptives would have the woman taking hormonal pills without any breaks at all.

Additional Notes

Skipping a hormonal pill will increase the risk of pregnancy and may worsen some adverse effects. If the pill is not taken at the same time when it is normally administered, it is advised to take the pill as soon as they remember later in the day. Oftentimes, you will not need to contact the pharmacist or doctor until you start missing three or more pills as unintended pregnancy may be a consequence and emergency contraceptives may be required if they had unprotected sex (3). If a non-hormonal pill is missed, there is no increased risk of pregnancy, and the non-hormonal pill may be discarded.

Hormonal pills can be started at any time of the month if the woman has not been taking another hormonal method or switching over from a non-hormonal method such as a copper intrauterine device. Alternatively, if they have been exposed to other hormonal-type contraception, the doctor will have to consider what was used to determine when it would be the right time to switch over to oral combination pills.

Benefits 

There are known non-contraceptive health benefits to using combined oral contraceptives including reduced risk of colorectal, endometrial (lining of the uterus) and ovarian cancer, as well as ovarian cysts (2, 4-7). In fact, studies have shown that long-term use of combined oral contraceptives (i.e., more than ten years) will provide the largest benefit for reduced ovarian (21 to 40%) and endometrial (34%) cancer rates (2). Women with iron deficiency anemia may take prescribed combined oral contraceptive pills to decrease the amount of blood loss and menstrual bleeding problems when the lining of the uterus sheds. Moreover, their use can reduce the severity of menstrual cramps and pain. Lastly, estrogen-containing pills can treat hormonal acne by reducing the number of acne lesions (2).