What is your fertile window?
There is only a specific time in each menstrual cycle when it’s possible to get pregnant. This ‘fertile window’ is once a month, generally close to the time of ovulation when the woman ovulates and releases an egg approximately 2 weeks before the next period is due. Men do not have a ‘fertile window’ because sperm is continually formed and stored in the testicles, ready to be used at any time.
An analogy
Let’s get our heads around the importance of timing with an analogy. If sperm were commuters, the egg would be a bus, and the fallopian tube would be the bus stop. The sperm-commuters can arrive up to 4 or 5 days early for the egg-bus. They can happily hang
out and wait this long. Much later, they begin to drop off. When the egg arrives, it’ll wait for about 24 hours. Sperm arriving during this time can also get on the bus. But if the sperm-commuters arrive a day late, the egg bus will be gone and the next one will not arrive for another 28-ish days.Having sex during the 2 to 3 days before ovulation gives a couple a 1 in 5 chance of conceiving.
This is the most fertile time of the month. Identifying your fertility window is about making sure the passengers are already waiting at the
bus stop.
Usually, the four primary fertility signs which ovulating women show are changes in:
- Basal body temperature or waking temperature
- Cervical fluid or mucus
- Position of cervix
- LH surge
Basal body temperature (BBT) or waking temperature
Basal Body Temperature Chart
The basal body temperature (BBT) is the temperature of the body on waking. It is called basal because it is measured at a time when the body is deeply rested and the body’s metabolism is at its baseline.
A woman’s BBT rises after she has ovulated and begins to produce progesterone. A woman’s pre-ovulatory BBT typically range from about 97.0 (36.1 C) to 97.5 (36.4C) degrees Fahrenheit, with postovulatory temperatures rising to about 97.6-98.6.(36.4 -36.9C) After ovulation, they will stay elevated until her next period. If she were to become pregnant, they would remain high throughout her pregnancy.
Temperatures typically rise within a day or so after ovulation and are the result of the heat inducing hormone, progesterone. Usually, the rise in temperature signifies that ovulation has already occurred. It does not reveal impending ovulation, as do the other three fertility signs, the cervical fluid, LH surge and cervical position.
When interpreting temperatures, the key thing to do is to look for a pattern of lows and highs. See the whole, rather than day-to day changes.
Certain factors can increase your BBT, such as:
- Having a fever
- Drinking alcohol the night before
- Getting less than three consecutive hours sleep before taking it
- Stress
- Taking is at a substantially different times than usual
- Using an electric blanket or hot water bottle that you normally don’t use
The BBT chart can indicate not just your fertile period and best timing, but can be show up issues such as:
- short luteal phase
- thyroid problems
- anovulation
- low progesterone
- hormonal imbalance (PCOS)
- very early miscarriage
Cervical fluid or mucus
Cervical fluid or mucus is to women what seminal fluid is to the man. Men produce seminal fluid continually because they are always fertile. Women, on the other hand are only fertile the few days around ovulation, and therefore only produce the substance necessary for sperm nourishment and
mobility during that time.
Changes in cervical fluid
As you approach ovulation, your cervical fluid gets progressively more lubricative. It may changefrom being sticky to being creamy or lotion like, and then to resembling raw egg white. At this time,it’s slippery and can stretch. You may also notice that the fluid is wet and that you feel a lubricative
vaginal sensation.
After oestrogen has peaked, the cervical fluid changes abruptly, sometimes within hours. There will be a drying of the fluid and the lack of cervical fluid will usually last the duration of the cycle. Finally, just before menstruation, you may notice a wet and watery sensation, which is due to the
drop in progesterone
Factors which can affect cervical fluid are:
- Vaginal infections
- Seminal fluid
- Spermicides and lubricants
- Some medication such as antihistamines, antibiotics, anti-inflammatories, antidepressants
- Coming off the contraceptive pill
Cervical position
Your cervix, the lower part of the uterus, which extends into your vagina, goes through cyclical changes throughout the cycle. As the hormones signal the approach of ovulation, the shape, position and texture of the cervix change.
As with the cervical fluid, the cervix prepares itself for a pregnancy by becoming soft and open around ovulation in order to allow the sperm to pass through the uterus. In addition, the cervix also rises due to the oestrogenic effect on the ligaments that hold the uterus in place.
So the cervix goes from being firm like the tip of your nose to becoming soft and mushy as you approach ovulation. In addition, it is normally fairly low and closed, and rises and opens around ovulation.
Luteinising Hormone (LH) Surge
The surge in LH produced by the pituitary gland last 24 to 48 hours and is responsible for triggering ovulation. This surge also coincides with the slippery/stretch cervical mucus. LH levels can be monitored using test /OPK strips starting from about day 9 of a 28 day cycle. Often women with
high LH levels (PCOS) often have problems using these .
Secondary fertility signs
Many women notice other signs and these can be practical information to identify fertile and infertile phases:
- Midcycle spotting
- Pain or achiness near the ovaries
- Increased sexual feelings
- Abdominal bloating
- Increased energy levels
- Heightened sense of vision, smell and taste
- Water retention
- Increased sensitivity in breasts and skin
Sources Lyttleton J (2004) Treatment of Infertility with Chinese Medicine Churchill Livingstone Toni Weschler (2003) Taking Charge of your Fertility Vermillon www.fertilityfriends.com
