Combination pills are oral contraceptives that combine ethinyl estradiol and progestin, similar to the natural sex hormones (estrogen and progesterone) produced in a woman's body. All combination pills contain estrogen (though they can differ in the amount of estrogen). Combination pills are different from one another based on which type of progestin that is included in the pill. Additionally, a distinction is made based on the way the estrogen and progestin is dispersed over the course of the pack of pills. Progestin are also categorized based on the effects it may have on the female body in terms of progestational, estrogenic, and androgenic activity.
Understanding the Categories of Combination Pills
Combination pills are categorized as monophasic, biphasic or triphasic depending on whether the level of hormones stays the same during the first three weeks of the menstrual cycle or if it changes. Keep in mind that for 28 day pill packs, the pills for the fourth week are usually placebo pills that contain no hormones.
Despite the hormonal differences, no single pill brand or pill type tends to outrank all the others. All combination pills are equally effective in preventing pregnancy, provided the pills are used consistently and correctly.
Multiphasic Birth Control Pills
Multiphasic oral contraceptives were developed in the 1980s. Phasic birth control pills include varied amounts of hormones which are designed to be taken at specific times throughout the course of each pill pack. These pills were developed to help lessen the side effects of monophasic birth control pills. When compared to monophasic combination pills, some phasic birth control pills tend to lower the total hormone dosage a woman receives throughout each pill pack; they are also designed to more naturally mimic the female body's menstrual cycle.
Monophasic Birth Control Pills
Monophasic pills are oral contraceptives that have the same amount of estrogen and progestin in each active pill in a pack. Due to the consistent hormone level in each pill, monophasic pills are less likely to cause side effects that may stem from fluctuating hormones. Monophasic pills are classified by their estrogen level:
- Low dose pills have the least amount of estrogen (20 mcg)
- Regular dose pills contain 3035 mcg estrogen
- High dose pills have about 50 mcg of estrogen
Monophasic birth control pills work as well as the more costly and complicated phasic options; low estrogen, monophasic pills may cause less bloating or breast tenderness, yet may result in more spotting. Most women find that a monophasic pill brand tends to be a good first choice.
Biphasic Oral Contraceptives
Biphasic birth control pills alter the level of hormones once during the menstrual cycle. Biphasic pills deliver the same amount of estrogen each day, but the level of progestin is increased about halfway through the cycle. Although the estrogen level remains the same, during the first half of the cycle, the progestin/estrogen ratio is lower to allow the endometrium to thicken as it normally does. During the second half of the cycle, the progestin/estrogen ratio is higher to allow for the normal shedding of the lining of the uterus. The first 7 to 10 days are one strength (and usually one color), and the next 11 to 14 pills are another strength (and another color). The last 7 tablets (if included) are placebo pills and contain no hormones.
Triphasic Birth Control Pills
Triphasic combination pills contain 3 different doses of hormones in the 3 weeks of active pills, so the hormone combination changes approximately every 7 days throughout the pill pack. Depending on the brand, the amount of estrogen may change as well as the amount of progestin. In a single month's supply, triphasic pills may have a gradual estrogen increase and/or some pills may also increase the dose of progestin. Therefore, since there are 3 different strength combinations in each pack, the first third pills consist of one strength (and one color). The next 5, 7 or 9 pills are another strength (and another color). The final phase of pills are a different color. The last 7 pills (if included) are placebo pills and contain no hormones.