The diagram below depicts the different phases or stages of a menstrual cycle. The length of each phase varies from woman to woman and hence not specific. An undestanding of the menstrual cycle is a tool used in natural family planning (fertility awareness) to avoid unwanted pregnancy. 



The first day of menstruation is the first day of a new menstrual cycle. Menstruation last between 3-6 days. During this time you pass out menstrual blood. Menstrual blood is a combination of blood and tissues resulting from the uterus shedding off its lining if a woman fails to get pregnant. It happens so that it can prepare the womb afresh again. Not all vaginal blood flow is menses. Some can be caused by stress or a disease. A true menstrual blood should flow 10 to 16 days after ovulation.


Infertile Phase A

This phase can be present or absent completely in some women depending on the length of their menstrual cycle. A menstrual cycle can last anything between 21-40 days. But on an average it will last for 28 days. For women with a short menstrual cycle (21-24days), this phase is usually absent and they will move immediately into the fertile phase (03.) after menstruation. This means she may get pregnant if she has sex during menstruation or immediately after menstruation. The length of the infertile phase A increases depending on the length of your menstrual cycle. The longer the length of your menstrual cycle the longer the phase. 


Fertility Window

This is the time when a woman can conceive and it can last up to 9 days; 6 days from the start of the fertility window up to the day of ovulation plus 3 days after ovulation. Your chances of getting pregnant are higher 2 to 3 days before ovulation. But before this stage or phase, 3 major changes may be observed in a woman during the other phases. 

  1. The Cervical os opening: The cervical os which is the lower part of the cervix that connects the vagina and the uterus is surrounded by white sticky and mesh-like mucus. This mucus does not stretch and is acidic in nature. During the infertile phase A and B it is completely closed and will allow nothing to pass through while during menstruation, it partial opens to allow the flow of menstrual blood.
  2. Texture and position of the cervix: During menstruation and during infertile phase A and B, the cervix appears lower in the vagina canal and feel firm to the touch just like the tip of your nose.
  3. The vagina generally appears dry and not wet provided you are not arouse sexually

But when you enter into the fertility phase or window, changes starts to occur: 

  • The cervical os is open completely to allow passage of the sperm
  • The cervix rises up the vagina and appears soft and moist. It becomes softer and moister as you approach the peak of your fertile window which is ovulation. In the event that pregnancy occurs, the cervix will remain up and softer but the cervical os will be tightly closed.
  • About 6 days to ovulation and at the beginning of the fertile window, the white, dry and sticky mesh-like mucus surrounding the cervical os begins to change into a wet, white and creamy mucus. This mucus is alkaline in nature and as ovulation approaches, it becomes more watery, abundant, clear, slippery and stretchy just like raw egg white. The clear white mucus can sometimes be stretched apart using 2 of your fingers. So during this period your vagina will appear wet. All these changes are nature’s own way to assist the sperm to swim smoothly through the vaginal canal into the uterus. But immediately after ovulation, the cervical mucus begins to dry up and the slippery and stretchy mucus become replaced by white, dry and sticky mesh like mucus. This may takes 3 days from the day of ovulation. Monitoring changes in vagina mucus can help determine when you are in your fertile window and when you will get pregnant.
  • Ovulation marks the most fertile day in a woman’s menstrual cycle and if you have sex on this day, you will have a high probability of getting pregant except if you have a disease that makes it difficult for you to conceive.

Ovulation is the release of an egg by the ovary

  • Once released, an egg can survive 12 to 24 h. A sperm can survive 3-6 days in a woman’s reproductive system. Therefore, if you have sex 6 days before ovulation, you can still get pregnant and as ovulation approaches, the chances of getting pregnant increases. Occasional, a second egg can be released 24 h after the first one. So pregnancy can still happen in some cases up to 3 days (D1, D2 and D3) after ovulation. But 3 days (D1, D2 and D3) after ovulation you become completely infertile. So when you understand your menstrual cycle and know when ovulation occurs, avoid sex 6 days before ovulation and 3 days after ovulation. If you need sex badly during this period, then use protection such as condom (a quality one).
  • Ovulation occurs from day 10 to day 21 of the menstrual cycle depending on the length of your cycle.
  • From ovulation to the next menstrual cycle usually takes between 10 to 16 days. This phase is also called the luteal phase. But in rare cases, the luteal phase may occur as low as 8 days after ovulation. This may be normal in some instances while in others, it could signal a fertility problem.
Other Signs
  • Luteinizing hormone (LH) is a hormone released by your brain which triggers ovulation. LH levels begin to rise and peak about 12 h to 36 h before ovulation. Test kits sold at the pharmacy can be used to monitor your LH levels and hence determine when you are about to ovulated.
  • Some women experience minor cramps or sharp pain on one side of the pelvis (lower abdomen) when they are about to ovulate. If this occurs somewhere midway along your menstrual cycle, then it is ovulation pain. Ovulation pain is a temporal thing but in some women it becomes so severe that they can’t even have sex during their most fertile time.
  • At the start of the fertility window, right up to ovulation, women usually experience an increase in sexual desire. A strategy by nature to ensure a woman gets pregnant. So as a woman you might experience increase in sexual desire during one phase of your menstrual cycle than the others. However other factors such as stress, depression or anxiousness can cause an increase in sexual desire as well. So be mindful when interpreting such a change.
  • Immediately after ovulation, there is a slight rise of about 0.3 to 0.8 oC in your basal body temperature (your temperature immediately before you get out of bed). This slight rise in temperature can be monitored using a basal temperature thermometer from the pharmacy and may last until the beginning of the next menstrual cycle or throughout your entire pregnancy in case where you fall pregnant. Note that this rise in temperature only occurs after ovulation and will not signal you on when exactly your fertility began. But it will help you to determine your fertility window. The temperature rise will fall down when you start menstruating.


Infertile Phase B

 Starts about 3 days after ovulation. During this time the vagina appears dry, the cervix is lowered and hard like the tip of your nose, the cervical os is covered by white and sticky mesh-like mucus and your basal body temperature is slightly raised. There is also a fall in your sexual desire and your breast may become tender (usually mistaken for a sign of pregnancy).