How to calculate a woman’s fertile period

The chances of pregnancy by calculating a woman’s fertile period are often done by couples. The fertile window is the period in the menstrual cycle when a woman’s chances of getting pregnant are highest. This period occurs when an egg is released from the ovary (ovulation) and is available to be fertilized by sperm.

Why is the fertile period important?

• For couples trying to conceive, this is the best time to have sex.
• For those who want to avoid pregnancy, understanding the fertile period helps to regulate sexual intercourse or use contraception.

How to Calculate Fertile Period

Accurately calculating a woman’s fertile window requires understanding the menstrual cycle and using data that can be supported by research. Here are general steps based on medical literature:

1. Recognize the Menstrual Cycle

The menstrual cycle is calculated from the first day of menstruation to the last day before the next menstruation. The average cycle lasts between 21-35 days.

2. Ovulation Identification

Ovulation usually occurs about 14 days before the next menstruation. At the time of ovulation, an egg is released from the ovary and is ready to be fertilized.

3. Fertile Period

The fertile period is the period around ovulation, which includes:

• 5 days before ovulation: Sperm can survive in the reproductive tract for 3-5 days.
• 1 day after ovulation: The egg can survive for 12-24 hours after it is released.

Thus, the fertile window usually covers the 10th to 17th day of the average menstrual cycle (28 days).

4. Scientific Approach Method

According to research journals, some methods can help calculate fertile days more accurately:

• Calendar Method
  Record menstrual cycles for several months to calculate the average cycle length. Use the following formula:
  • First day of fertile period: Shortest cycle length – 18.
  • Last day of fertile period: Longest cycle length – 11.
• Basal Body Temperature (BBT) Observation
  Basal body temperature increases by about 0.3-0.5°C after ovulation. Temperature measurement every morning before activity can help identify ovulation.
• Cervical Mucus Changes
  As ovulation approaches, cervical mucus becomes clearer, elastic and slippery (like egg white). This signals the fertile period.
• Ovulation Kit
  An ovulation test kit that detects spikes in luteinizing hormone (LH) can be used to predict ovulation.