Can you get pregnant on your period?

So after a lot of research and many discussions, we can, in fact, confirm that you are super unlikely to get pregnant on your period! Here is why: Medical advice has always erred on the side of caution, and the internet is full of advice that you can get pregnant at any point in your cycle. Although, you can never be 100% sure of pregnancy risk, it is fair to say that you are more at risk at a certain point of your cycle than at others. To fully understand the chances and how this can happen, first, you’ll need to understand how pregnancy happens. So let us explain… it’s all about egg and sperm meeting! Sounds simple, but here is the maths….

• If you have a regular menstrual cycle, you are likely to be ovulating once a month
• The earliest date of ovulation is 14 days before your period starts and an egg survives for up to 24 hours after it is released from the ovary
• Sperm can live up to 7 days in the female reproductive tract.¹  Although the mean survival time has been estimated to be 1.47 days with less than 5% probability of sperm surviving more than 4.4 days.²
• There is therefore a ‘fertile window’ each month when it is possible for an egg to meet sperm and a pregnancy can happen.

This maths doesn’t work if you take hormonal contraception or have taken the emergency contraceptive pill (morning-after pill) in your last cycle.

How do I calculate my earliest ovulation day?

This can be calculated if you have a regular cycle. It is a bit more tricky to predict if you have irregular cycles, but not impossible. Day 1 = first day of your period The earliest ovulation date is your cycle length minus 14 days If you have a 28 day cycle, earliest date of ovulation is 28 minus 14 = Day 14 If you have a 35 day cycle, earliest date of ovulation is 35 minus 14 = Day 21 It is a bit hard to explain this information clearly for each individual, and it requires you to have an accurate record of the lengths of past menstrual cycles, hence why healthcare professionals tend to use the blanket advice that you can get pregnant at any part of your cycle.

Know your cycle

Using this knowledge to help prevent pregnancy is only advised for those who have a good idea of when they are ovulating i.e. those who use Fertility Awareness Methods (FAM) where you monitor changes in your body such as daily body temperature and cervical mucus changes to predict ovulation. If you have unprotected sex at any point in your cycle and aren’t using FAM then you still need to use emergency contraception as you can’t be sure when you have ovulated based on your menstrual data alone.

Can you get pregnant on your period?

If you have a regular and normal length cycle (around 28 days) and you have not used emergency contraception pills in your cycle, you can’t get pregnant on your period (technically speaking this means during days 1 to 6 of your menstrual cycle with day 1 being the first day of your period). This is because if you have a 28-day cycle, the earliest date of ovulation is 28 minus 14 = day 14.  Sperm lasts up to 7 days so if you had sex before day 6 sperm won’t be around by the time of ovulation to meet an egg.

Cycle lengths can vary between individuals but the average length is 28 days with most cycle lengths between 25 to 30 days.³ If you have a shorter cycle length then there is more risk of egg and sperm meeting. For example, if you have a 23-day cycle, the earliest date of ovulation is 23 minus 14 = day 9 (day 1 being the first day of your period).  Sperm lasts up to 7 days so if you had sex after day 2 of your menstrual cycle whilst on your period there is a potential risk of egg meeting sperm. As mentioned before, if you have unprotected sex at any part of your cycle and are not using FAM you need to consider emergency contraception just in case. This is because your cycle length (and day you ovulate) has the potential to vary month to month so these calculations alone should never be used to predict your fertile window or when it is safe to have sex.

Can I get pregnant during my period on combined birth control?

In short, no – you cannot get pregnant when you have a withdrawal bleed on combined hormonal contraception. If you are using combined contraception (e.g. the combined pill, patch or vaginal ring) correctly and consistently, then you should be protected against pregnancy all the time, which includes during the scheduled seven-day (or shorter) break, or the days you take your placebo pills, when you may experience a withdrawal bleed like a period. You can still have sex during this week without getting pregnant, as long as you took the last packet of pills correctly and start the new pack correctly.

Can I get pregnant just before my period?

The probability of pregnancy if you have unprotected sex a couple of days before your period is very slim but unless you are tracking your cycle and using FAM, you still need to consider emergency contraception. Your fertility window closes soon after you ovulate, this is because an egg only lives for around 24 hours after it is released from the ovary, which is approximately 14 days before your period starts so there is no opportunity for the egg and sperm to meet.

How many days after my period can I get pregnant?

The number of days after your period when ovulation can occur varies between people and can change from month to month. Everyone has different cycle lengths, which is why we calculate your earliest date of ovulation as 14 days before your period starts (i.e. we only know once your next period has already started).  If you have a very short cycle, ovulation could happen relatively soon after your period stops. For example, if you have a 25 day cycle the earliest date of ovulation would be (25 minus 14 =) day 11. Sperm can live for up to 7 days, so if you have sex from day 4 of your cycle, you could get pregnant.

Can I get pregnant during my first period after giving birth?

You can get pregnant before your first period after a pregnancy. After giving birth, the earliest possible ovulation date is 21 days after birth. On average, ovulation takes a bit longer, especially if you are breastfeeding. If you are having sex in the first few months after having a baby, then you need to start contraception before three weeks post-baby arrival. Ovulation will happen before you have a period, and many people get caught out by this! We have written a handy blog about contraception after a baby.

Can I get pregnant during my first period after an abortion?

You can get pregnant before your first period after an abortion. The advice about ovulation after an abortion varies, but it is true that you can ovulate and get pregnant before you have a period. Abortion providers say you can ovulate as soon as five days after an abortion.⁴ It is recommended that contraception is started within five days of abortion to ensure no risk of ovulation and unintended pregnancy.⁵

Does tracking my cycle really help?

Yes, tracking your cycle can help you to understand your fertile window, especially for those who do not want to use hormonal contraception.  Understanding your cycle is the key to empowering yourself with the tools to understand pregnancy risk. Apps to help track your cycle can help to build a picture of ovulation and lengths of cycles but shouldn’t be used for contraception. There are various period tracking apps around, however if you’re looking to use a fertility awareness app for contraception the Natural Cycles app is a CE-marked medical device.⁶ The Natural Cycles app contains an algorithm that analyses your temperature (measured using a thermometer), menstrual cycle data and optional LH (luteinizing hormone) tests to calculate when you are fertile, and tells you to avoid sex or use other protection like on your fertile days. Other more traditional fertility awareness methods require you to use a combination of indicators of ovulation and work out your fertile window manually. To do this we recommend you get support from a fertility awareness practitioner. The NHS website recommends you use a Fertility UK practitioner – you can find one on the Fertility UK practitioners site here.

Does this mean I can have unprotected sex at different times in my cycle?

It depends!! Yes – if you are using a FAM where you are calculating ovulation and your fertile window. FAM uses multiple different signs and symptoms to predict when you are ovulating and when you need to use extra protection. You should not be just using the dates of your period as your only data. No – if you are not using FAM then you still need to use emergency contraception as you can’t calculate when you have ovulated and therefore might be at risk of an egg and sperm meeting. This is why the emergency copper coil is so great as it can be used up to 5 days after unprotected sex or up to 5 days after the earliest date of ovulation, giving you a longer window than the morning after pill to prevent unintended pregnancy. Toggle Title Dr Becky is part of The Lowdown’s medical team. She works as a GP in Sheffield where she fits and removes coils and implants, and has previously worked in fertility services and sexual health clinics. Becky also works as a researcher looking at improving access to sexual and reproductive healthcare.