Sperm lasts for quite a while inside the uterus, and some experts estimate it could survive for 5 days. While pregnancy can only occur during ovulation, it could pose a risk even if you don’t have sexual activity during it.[1]
Most women ovulate around two weeks into their menstrual cycle. That doesn’t mean that you can have unprotected sex outside this window with zero pregnancy risks; this happens because of the 5-day rule already mentioned.
Furthermore, not all women have the same cycle length. Most average at 28 days or so, but some women experience shorter cycles. For the latter, pregnancy can be a possibility even if sex occurs during periods.[2]
For instance, you could conceive if you ovulate early and had sex at (or near) the end of your period. That’s why condoms and other birth control methods are always advised even outside ovulation.
How does ovulation work for pregnancy?
Ovulation refers to the process in which the ovary releases a mature egg through the fallopian tube. This happens around once per month, and pregnancy occurs when sperm reaches this egg in the fallopian tubes or uterus.[3]
The egg lasts for up to 24 hours after leaving the ovary. The sperm can do the same for up to 5 days inside the uterus. Egg implantation after fertilization takes between 6 and 12 days after ovulating.
That’s why it’s possible to get pregnant right after the period; you’re approaching the fertility window. However, it’s also why it’s really difficult to get pregnant by having sex right before having your period.
If you track ovulation, then you’ll have lower chances of conceiving if you wait for a couple of days after ovulating. Likewise, pregnancy chances continue to decrease as you approach your period.[4]
Menstrual periods begin when fertilization doesn’t occur, and the uterine lining sheds.
Fertility tracking
Tracking fertility is one of the main strategies when trying to get pregnant. Conversely, it’s also helpful when preventing it. If you wish to use it as a birth control method, then it’ll require several months before you can determine your fertility windows accurately.
- How to do it
You first need to record which day your menstrual period starts, and count how many days it lasts. Day 1 should be the first day you experience full flow. You want to do this for several months; a whole year is best.
You then want to annotate both the shortest and longest amount of days you got from on your monthly tracking.[5]
Go to the shortest cycle and subtract 18 days from its length and write down the resulting number. Now, go to your longest cycle and subtract 11 from its length and write down the result.
Your fertile window should be the period between both results. For instance, if your shortest cycle was 28 days and the longest was 30, then your fertile window is from day 10 to day 19. These days, you want to avoid having sex.
There are tools you can use to track your menstrual cycle as well. You can find fertility apps for free that let you do this. You can also use a regular calendar, but these apps are more intuitive.
- Using it as birth control
Your ovulation starts between your fertile window. That released egg is then viable for a day, so you won’t get pregnant during the entire window. This period is to keep you from risking pregnancy by either having sex during ovulation or having live sperm in your uterus by the time it happens.[6]
Is fertility tracking as effective as you would like?
If your menstrual cycle is regular, then tracking this fertile period is helpful for preventing pregnancy. However, even regular cycles can change every month, especially with factors related to your diet, emotions, or physical condition.
This is why the fertile window is so broad despite the egg lasting for a day. Fertility tracking is more helpful for aiding pregnancy than for preventing it. It’s always advisable to use additional birth control methods.[7]
Similar methods
Here are some of the methods you need to implement.
- Basal temperature
Basal temperature refers to your body temperature while resting. This temperature increases a bit during ovulation, and tracking it requires a special thermometer.
The method is basically tracking your temperature right after waking up before you get up. You then write it down and repeat the process every day. There are apps for this as well. If you notice a slight rising in temperature (under 0.5°C), then you’re ovulating.[8]
The method works better if you wait to have sex after your temperature has gone up and down again.
- Cervical mucus
Some women experience increased amounts of cervical mucus when they’re about to ovulate. It’s thanks to an increase in estrogen levels.
Cervical mucus during ovulation is clear and thin; you could compare its consistency to egg whites. If you notice an increase in cervical mucus around your fertile window, then you can be assured you’re fertile.
- Predicting kits
There are also special ovulation predictor kits that you can use to test urine and check for increases in LH (luteinizing hormone) levels.[9]
This hormone surges around a day or two before ovulation begins. Therefore, you want to avoid having unprotected intercourse during – and a while after – this hormonal spike.
The problem with using predicting kits for birth control is that sperm can live for several days inside the uterus. If you have unprotected sex and record an LH surge a day or two afterward, then you’re at risk of getting pregnant.
Most effective contraception methods
The menstrual cycle can change quite a lot, so using it as your sole contraception method can be dangerous if you don’t want to risk pregnancy.
The most effective contraception methods are usually hormone treatments, which tend to offer over 99% effectiveness when used correctly. Popular approaches are birth control pills, IUTs, and contraceptive injections.[10]
However, condoms are also very effective when used properly, and they’re the only birth control method that protects you and your partner from STIs.
Conclusion
Pregnancy only occurs when a mature egg is fertilized during ovulation. This egg is only viable for a day every month, and sperm can live up to 5 days inside the uterus. Therefore, it can be quite difficult to become pregnant unless you track your cycle.[11]
It also means than tracking your cycle can go a long
way in preventing pregnancy, but it shouldn’t be your only contraception
approach. Since the menstrual cycle varies a lot, it can be difficult to
keep track of the days when it’s safer to have unprotected sex.
The best way to use “safety periods” is to
complement another birth control method with th
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5469003/
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