March 3, 2024

I, Science

The science magazine of Imperial College

Kaylee Gregor teams up with medical specialists to have your contraceptive curiosities answered! A no BS, to the point Q&A is now in session.

Kaylee Gregor
26th August 2021

Q: “How does the pill actually work?”Sophie, 25

A: The combined oral contraceptive pill (COCP) is made up of two hormones- oestrogen and progesterone. These are synthetic hormones made in a lab which act the same way our natural sex hormones do in the body.

“They have different combinations of the amount of oestrogen and the type of progesterone in them” says Mr Kevin Hayes, a consultant Gynaecologist at St George’s Hospital. The doses are deliberately more hormones than you would ever experience on your natural cycle to supress the area of the brain responsible for our hormone levels in the body. This suppression stops ovulation. You cannot get pregnant if you do not ovulate.  

Additionally, the net effect of the doses in the combined pill is to thin the endometrial lining, creating a hostile environment for an egg, “so even if you were to ovulate, you don’t implant” says Hayes.

Q: “Does it make me moody or am I just a b*tch?”Emily, 26

A: It’s a bit hard to tell. Hayes explains, “we know it affects people’s emotions and psyche. There is no doubt that if you give people hormones that are absorbed into the body, it can affect them in less than ideal ways.”

Whilst oestrogen and progesterone are primarily sex hormones, they will still affect every system in the body, including your brain!

“Changes in mood are recognised (in the same way mood can change around periods)” says Dr Polly Cohen, who specialises in community sexual and reproductive health. “It’s all a bit trial and error to find which contraceptive works best for you.”

Feelings of depression, anger and tearfulness can occur while on the pill. They aren’t one-size-fits-all, so change it up if you’re feeling down.

“Of course,” she adds,  “mood can be affected by everything from diet to exercise to life stressors – so it might not all be down to the contraception!”

Q: “Asking for Hot Girl Summer- Is it safe to skip my period week?”Amy, 20

A: Yes! “There is no harm in doing this for prolonged periods of time” explains Hayes.

Your “period” while on the pill is not a true period at all. It is actually a withdrawal bleed from stopping the hormones.

True periods clear out the egg and endometrial lining of the uterus which have been working to create the cosiest environment for an egg to implant in. When implantation doesn’t occur, these layers shed and the cycle starts all over again. On the pill, the endometrial layer remains thin, which is why  withdrawal bleeds are typically lighter than your regular period, and may be skipped safely.

Q: “After I got off the pill my hormones were crazy and I swear I have never been the same since. Can this happen?” -Heili, 24

A: Unfortunately it can. “Some people when they go on the pill weren’t having problems then suddenly develop them” says Hayes, although this is uncommon.

Q: Am I protected if I miss a pill? -Harriet, 26

A: It depends on which pill in your cycle you miss.

Hayes says that “you must not miss the pills at the end of the pack or beginning of the next pack.” This is because the hormone suppression on the brain lasts 10 days. “That 7 day break all of a sudden becomes 8, 9, 10 and you will ovulate next cycle.”

He recommends that if you miss pills near the end of your pack, do not have a break and start your next pack straight away. And if you miss pills in the first week, to use condoms.

Q: “How is contraception effectiveness measured? I don’t get it.” -Daisy, 28

A: Let’s talk numbers. Contraception effectiveness is measured by how many women out of a 100 will become pregnant while using the contraception method per year.

“It’s all the sex those women have in the year, whether it’s once or 100 times, it doesn’t matter,” says Hayes. The statistics account for life’s ups and downs (we agree, it’s hard to remember to take a pill every day!)

Without any form of contraception, 85 in 100 women would become pregnant per year. On the pill this statistic is 8 in 100 women per year.

For more information on finding a contraception right for you, visit (recommended by Dr Polly!)

Kaylee Gregor is our online features editor and studies Science Communication at Imperial College and medicine at St Georges University of London.