Oestrogen vs Progestogen: Which Contraceptive Pill Might Be Right for You?

What are oestrogen and progesterone?
How does oestrogen help prevent pregnancy in contraceptive pills?
Combined Contraceptive pills
How does progestogen help prevent pregnancy in contraceptive pills?
Progestogen-only contraceptive pills

Hormonal contraceptives are methods of birth control that use synthetic versions of the naturally occurring female hormones oestrogen and/or progesterone to help prevent pregnancy.  

There are different types of hormonal contraceptives, such as contraceptive pills, patches, injections, implants, rings, and the IUS (intrauterine system). Some of them contain both oestrogen and progestogen (the synthetic version of progesterone), whilst others only contain progestogen.

What are oestrogen and progesterone?

Oestrogen and progesterone are hormones which play a crucial role in mammalian reproduction. 

Oestrogen has various functions including helping with bone growth and regulating our moods, but is best known for its role in female growth and reproductive development. It helps maintain the menstrual cycle and facilitates the preparation of the uterus for anticipated and actual pregnancy.

“Oestrogen plays a role in ovulation (when your ovaries release an egg) and thickens the lining of your uterus (endometrium) to prepare it for pregnancy,” says Dr. Hana Patel*, GP Expert Witness. “Oestrogen causes eggs to mature in ovaries once a girl hits puberty. These are then released at regular intervals during the menstrual cycle. It’s responsible for helping several organs function, including stimulating growth of the egg follicle in the ovaries, maintaining vaginal lubrication, maintaining the mucous membrane that lines the uterus, and the formation of breast tissue.

Oestrogen has a role outside the reproductive system too, with effects on bones, skin, hair, the brain, the heart and cholesterol levels.

Progesterone is a steroid hormone that helps prepare both male and female bodies for reproduction. In females, increased levels of progesterone signal the body to thicken the lining of the uterus and the body will continue to produce progesterone during pregnancy to support the development of the foetus. High levels of progesterone also prevents your body from ovulating when you’re pregnant

“Progesterone is produced by the ovaries, and is released in the second half of a woman’s menstrual cycle after ovulation,” says Dr Patel. “The main function of progesterone is to prepare the endometrium (lining of your uterus) for a fertilised egg to implant and grow. If a pregnancy doesn’t occur, the endometrium sheds during your menstrual period. If conception occurs, progesterone increases to support the pregnancy.”

How does oestrogen help prevent pregnancy in contraceptive pills?

Synthetic versions of these naturally occurring hormones are used in contraceptive pills to help prevent pregnancy. They can do this by preventing ovulation so no egg is released and sperm which has entered the body has nothing to fertilise, as well as thickening the mucus in the neck of the womb so it’s harder for sperm to reach an egg. 

Oestrogen in contraceptive pills helps prevent pregnancy by suppressing the production of follicle-stimulating hormone (FSH), which is responsible for stimulating the growth and maturation of eggs in the ovaries. By lowering the levels of FSH, oestrogen helps prevent the ovaries from ovulating (i.e. releasing an egg each month). 

Without ovulation, there is no egg available for sperm to fertilise, therefore pregnancy cannot occur. Oestrogen also has some other effects that make it harder for sperm to reach the egg, such as thickening the mucus in the cervix and thinning the lining of the womb. Oestrogen is usually combined with another hormone called progestogen in contraceptive pills, which has similar effects that prevent pregnancy.

Progesterone is produced by the ovaries, and is released in the second half of a woman’s menstrual cycle after ovulation

Combined Contraceptive pills

Combined contraceptive pills contain both oestrogen and progestogen, and when used correctly they are over 99% effective at preventing pregnancy. Combined contraceptive pills are often (although not always) taken for 21 days, followed by a 7 day ‘break’ where you will usually take placebo pills in order to have a monthly bleed. There is no evidence that having a monthly bleed is medically necessary, but some people prefer to have it. If you are interested in starting a combined contraceptive pill, book an appointment with your GP to discuss your options.

Combined contraceptive pills are well tolerated by many people, but they may not be suitable for some women and people with uteruses for medical reasons, such as those who are over 35 years old and smoke, or people with a higher body mass index (BMI).  Combined contraceptive pills are also not suitable if you have a history of blood clots, or if you are allergic to or do not want to take oestrogen. For those people, a progestogen only pill might be more suitable.

How does progestogen help prevent pregnancy in contraceptive pills?

Progestogen is a hormone that, in progestogen-only contraceptive pills, helps prevent pregnancy by affecting the reproductive system in different ways. Depending on the type of progestogen-only pill, it may work by:

Stopping ovulation, the process by which an egg is released from the ovaries each month. This means there is no egg for a sperm to fertilise. This is partly how the newer progestogen-only pills that contain desogestrel work.

Thickening the mucus in the cervix, which is the entrance to the womb. This makes it harder for sperm to pass through and reach an egg. This is partly how the older progestogen-only pills that contain levonorgestrel or norethisterone work.

Everyone is different and the type of contraception that is right for you will depend on factors like your medical history and personal preference. In order to discuss your contraception options, you will usually book an appointment with your GP. As of 2021, some progestogen-only contraceptive pills like Hana® are available to buy over the counter or online.

Progestogen-only contraceptive pills

Progestogen-only contraceptive pills (sometimes referred to as mini pills) contain progestogen and do not contain oestrogen. Because of this, progestogen-only pills may be suitable for more people, including those who cannot or do not want to take oestrogen. Circumstances in which the progestogen-only pill may be suitable for you include:

If you’re over 35 and you smoke
If you’re breastfeeding
If you are allergic to or don’t want to take oestrogen
If you have a higher BMI
If you have a history of blood clots

There are different types of progestogen-only pills available which contain different active ingredients. As of 2021, some progestogen-only pills which contain the active ingredient desogestrel are available to buy over the pharmacy counter or online without a doctor’s appointment or prescription.

Before you are able to purchase a progestogen-only contraceptive pill in this way, you will complete a checklist so the instore or online pharmacist can determine whether this type of contraception is suitable for you. Pharmacists are experts in medicine and are more than qualified to check whether progestogen-only contraceptive pills are suitable for you. Find out more about the training pharmacists go through here.

When taken correctly, progestogen-only contraceptive pills containing desogestrel are over 99% effective at preventing pregnancy. They are usually taken every day at the same time without a break between packs. 

Everyone works differently and there’s no one size fits all when it comes to contraception. Many people may find that they need to try a few methods before they settle on something which works for them. You deserve to feel comfortable and secure in your contraception, so speak up if something doesn’t feel right.

*Dr Hana Patel does not endorse any products or brands

Hana® 75µg film-coated tablets contains desogestrel and is an oral contraception for women of child bearing age to prevent pregnancy. Always read the instructions on the package leaflet carefully.