Author
Bowtie Team
Updated on
2025-08-07
Disclaimer: This article is translated with the assistance of AI.
You’ve probably heard of the ‘safe period’ for avoiding pregnancy, but with so many calculation methods out there, which ones really work? Is the popular ‘seven days before and after menstruation’ rule reliable? Discover effective ways to minimize pregnancy chances—Bowtie breaks it down for you!
Can Calculating the Safe Period Help with Contraception?
In theory, unprotected sex at any time during a woman’s menstrual cycle could lead to pregnancy. Of course, accurately calculating the safe period can effectively reduce the chances of conception, but it requires long-term observation and recording. Plus, the length of a woman’s cycle can be influenced by factors like stress, diet, and exercise, meaning ovulation timing might vary each month—definitely something to keep in mind.
What is the Safe Period?
The safe period involves calculating a woman’s ovulation period to avoid sexual activity during this more fertile time, which is why it’s also known as the “ovulation calculation method.”
Calculating the safe period falls under “natural family planning,” meaning no contraceptives are used—just observing the woman’s menstrual cycle to lower pregnancy risks. In reality, for a more accurate ovulation estimate, you can’t rely solely on the “calendar method”; it should be combined with techniques like “cervical mucus observation” and “basal body temperature measurement.”
How to Calculate the Safe Period?
1. Calendar Method
The calendar method requires tracking menstrual cycles for 6 to 12 consecutive months. If cycles are stable and regular, it’s easier to predict the next ovulation. Here’s how to calculate it:
- Women can mark the first day of their period and the first day of the next period on a calendar—these mark the cycle length.
- Remember, before using the calendar method for contraception, you must have tracked cycles for at least 6 months.
- From the recorded cycles, identify the longest and shortest. For example, 31 days (longest) and 28 days (shortest).
- To find the first day of the fertile period (commonly called the danger period), subtract 18 from the shortest cycle. If the shortest is 28 days, 28 minus 18 is 10, so the danger period starts on day 10 of the cycle.
- For the last day of the danger period, subtract 11 from the longest cycle. If the longest is 31 days, 31 minus 11 is 20, so the danger period ends on day 20.
- Using this method, days 10 to 20 of the cycle are the danger period, while outside of that is relatively the safe period.
Besides this calculation, there’s a more traditional “standard calendar method” that considers days 8 to 19 as the danger period, suitable for women with cycles consistently between 26 and 32 days.
2. Cervical Mucus Observation Method
This method suggests women wipe the vaginal area daily to observe and record discharge. During ovulation, estrogen surges make cervical mucus (commonly known as white discharge) increase, becoming stickier and egg-white-like.
Note that cervical mucus secretion can be affected by factors like breastfeeding, birth control pills, STIs, or a history of cervical surgery.
3. Basal Body Temperature Measurement
This method requires measuring and recording basal body temperature (BBT) for 6 to 12 consecutive months, either by noting it down or using a phone app. Measure right after waking up, before getting out of bed.
BBT rises by 0.2°C to 0.6°C after ovulation and drops back to normal before the next period. So, women aiming to avoid pregnancy should steer clear of unprotected sex for 5 days before the BBT rise, up until the day after it increases.
4. Ovulation Self-Testing
Over-the-counter ovulation test kits or strips (priced from tens to hundreds of HKD) can test luteinizing hormone (LH) levels in urine. LH surges 24 to 48 hours before ovulation.
The tricky part is that sperm can survive in the uterus for up to 5 days, so women wanting to avoid pregnancy need to skip unprotected sex for 5 days before the LH surge.
5. Monitoring Physical Symptoms
Some women can feel physical changes during ovulation, like breast tenderness or mild ovarian pain. These signs can be combined with other methods to pinpoint ovulation and calculate the safe period.
What is the Pregnancy Risk During Safe Period?
By combining the “calendar method,” “cervical mucus observation,” and basal body temperature tracking for accurate safe period calculation, the success rate for contraception can reach 70% to 80%. Thus, the pregnancy risk during the safe period is about 20% to 30%.
Benefits of Safe Period Contraception
Many people aim to accurately calculate the safe period for contraception, as it offers these advantages:
- Avoids side effects from contraceptive pills , surgeries, and similar methods
- Suitable for religious reasons that prohibit drugs or condoms
- Can be stopped anytime when planning for pregnancy
- A low-cost contraception option
Drawbacks of Safe Period Contraception
While calculating the safe period for contraception has benefits, it also comes with several downsides:
- Calculations and tracking can be quite tedious
- Typically requires 6 months or more to observe cycles
- Without condoms, it doesn’t prevent STIs
- Harder for women with irregular menstrual cycles
- Requires abstinence or backup methods outside the safe period
Safe Period FAQs
Is the “7 days before and after menstruation” the safe period?
Absolutely not. This isn’t an accurate way to calculate the safe period. Use the methods mentioned above to determine the ovulation period and exclude that fertile window for a more precise safe period estimation.
Can you get pregnant from sex during menstruation?
Not necessarily safe—unprotected sex during menstruation can still lead to pregnancy. Sperm can survive in the uterus for 5 days or longer after intercourse. If a woman has a shorter cycle (average 28-30 days) and has unprotected sex near the end of her period, combined with early ovulation, the periods might overlap, increasing conception chances.
Plus, blood can transmit STIs, and bacteria thrive in menstrual blood, so it’s generally recommended to use condoms even during periods.
Other Topics
Blood HealthBowtie StoryBusinessCancerChinese MedicineCovidCustomer ReviewDeathcareDental HealthDigestive HealthDoctor SpecialistsDrugsEar, nose, and throatEndocrinology & DiabetesExercisingEye HealthFinanceFood & NutritionGroup Medical InsuranceHealthHealth GlossaryHeart HealthHospitalsHot TopicsImmigrationInsuranceKidney HealthKids HealthlearnLiver DiseaseLung & RespiratoryMedical Check UpsMen’s HealthMental HealthNervous SystemOrthopedicsOutpatient ServicesParentingPhysiotherapyPress ReleasePrevention/VaccinationProduct PhilosophyRealtyRheumatic DiseaseSeniors HealthSymptomsTreatment PlanUrologyWomen’s Health女性健康