The menstrual cycle

Fertility phases of the menstrual cycle explained, with information on the luteal and follicular phases and ovulation
A woman's menstrual cycle is affected by a complex interplay of hormones that prepare the body for ovulation. By understanding the different phases of the menstrual cycle you can begin to build up a picture of your own fertility pattern and consequently your time of peak fertility when you are most likely to conceive.

The average length

The first day of your period is considered to be day one of your menstrual cycle and although a 'typical' cycle is considered to be 28 days in length, this varies greatly between women with anything between 25-34 days being considered 'normal'. Cycle length can also vary from month to month, with up to 8 days variation between cycles still considered as a regular menstrual cycle.

The two menstrual phases

There are two distinct phases of the menstrual cycle, the follicular phase and the luteal phase. These are separated by ovulation and so are often known as the pre-ovulation and post-ovulation phases respectively.

The follicular phase

The start of the follicular phase coincides with the first day of the menstrual cycle and encompasses the time of menstrual bleeding. This phase is known as the pre-ovulation phase because it is the hormonal changes that happen during this time that prepare the body for, and eventually lead to ovulation. The length of the follicular phase can vary greatly between cycles as it is dependent on the development of egg bearing follicles in the ovaries - typically it can last anywhere between 13 and 18 days.

During the follicular phase the pituitary gland releases FSH (follicle stimulating hormone) which causes ovarian follicles to develop. Eventually one of these follicles becomes dominant and releases an egg. The maturation of the dominant follicle leading up to ovulation causes an associated increase in the hormone oestrogen. This in turn causes cervical mucus to become more facilitating to the movement of sperm and a thickening and nourishment of the lining of the uterus.


Your fertility increases throughout the follicular phase with the most fertile time considered to span 5 days before and 2 days after ovulation, with the most fertile day being the one before you ovulate. This is because the egg can be fertilised for up to 48 hours after leaving the follicle and sperm is able to survive in your body for between 3 and 7 days after being released.

The end of the follicular phase is marked by ovulation. While this typically occurs mid-cycle, its timing depends on the length of the follicular phase.

Once oestrogen production reaches a certain level, it signals to the pituitary gland that the egg is now ready to be released by the dominant follicle. The pituitary gland then produces the hormone LH (luteinising hormone) which triggers ovulation. The egg is released into the fallopian tube where it is ready to be fertilised by sperm.

The luteal phase

As ovulation marks the end of the follicular phase, it also marks the start of the luteal phase. This phase is known as such because of the key role the corpus luteum plays in this part of the menstrual cycle. The corpus luteum is the now empty dominant follicle that released the egg. After ovulation it releases the hormone progesterone which maintains the receptive uterine environment in case of fertilisation and implantation.

Fertilisation and implantation

If the egg is fertilised and implants in the uterus, the corpus luteum will continue to produce progesterone to nourish the embryo until the placenta begins to develop at the start of the second trimester. However, if the egg is not fertilised and does not implant, the corpus luteum will disintegrate after approximately two weeks, causing the drop in progesterone levels that signals the start of menstruation and the beginning of a new cycle.

Although the length of the luteal phase varies between women and can be anywhere between 12 and 16 days on average, it is this phase of the menstrual cycle that remains constant (i.e. always lasts 15 days). If an egg is not fertilised within 24 hours of ovulation, the rest of the luteal phase is considered to be relatively infertile.

Charting your cycle

Methods of charting the phases of the menstrual cycle can help you to predict when ovulation occurs. These include charting your basal body temperature (BBT - this tells you when ovulation has occurred), cervical mucus and cervical position (these help to predict when ovulation will occur). Additionally, hormone testing kits are also available to help you work out when you are most likely to conceive.

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by NWAKAEGO 20th Jun 2013, 3:43pm
Nice Posting!! Keep it up!!Main problem faced by women trying to conceive. It is necessary to know the RIGHT Day, RIGHT Time and RIGHT Way for conception…Now you can plan your pregnancy and you can choose your date and time of pregnancy as you like with Ovulation Kit.
by moni1122 20th Jun 2013, 3:42pm
by Mgbeojikwe 30th Nov 2011, 9:29am
I'm having about 3 to 5 days late for every monthly due period date,ex:September on 10 2010 is the lmp date..then this i almost being so stupid to think that im absolutely pregnant coz it coming to 10 days late (21/10/2010 lmp for this month) but this irregular period is start when im having sexual intercourse for 1st time with my fiancée start on February 2010. before this my menses is regular every on im n my fiance trying to get pregnant since the 1st time sex we made. but now on still does't not success...can anyone expert diagnose what actually happens to my fertility.
by pijaechay 27th Oct 2010, 3:42pm
Now I am planning for a baby. My last period was on 19th Sep,10. Can you pls. tell me the most fertile days to be get pregnant.
by mona1234lika 4th Oct 2010, 11:15am
i always see my ovulation, but when i have sex during my ovulation i donot get pregnet, what should i do.
by stellaomos 12th Aug 2010, 9:48am
i finished my period on thursday just past and started iit on the tuesday. exactly a week later i had unprotected sex three times in one night, what are my chances of being pregnant, help?x
by Emmaanderson 18th May 2010, 5:37pm
i am trying for a baby and have been trying for a few months...still unsuccessful but still keepin going. any advice on concieving
by hewins09 2nd Nov 2009, 10:31am
iv a very heavy cycle doues this stop a woman from conceving
by aril 8th Oct 2009, 9:34am
since i had my implant out 2 month ago i havent had any periods at all. before they were like clockwork but happened twice a month does this mean im not ovulating or what does this mean??
by lucyloo09 7th Oct 2009, 9:49am
I am interested in hearing is anyone elses period a bit messed up it was always 29 days then after having a misscarriage it was every 32 days and knew when to expect it now all of a sudden its back to 29?????
by Kmq 19th Sep 2009, 5:38pm
do breating affeccting d quatity of menstral flow
by osahon 18th Aug 2009, 9:22am
by ShareenElliisBabyx 8th Jun 2009, 9:43am
hello,when can i try to concieve?is it on the8day or is it on 10th to so streed i wan to have akid will b 36this yr.
by joss2009 30th Mar 2009, 9:40am
For those of you wanting to know when is the best time to have sex, or just track everything, go to and use the ovulation calendar. I am 40 and been trying to conceive for years, I never could until I used the calendar and within 2 months I was pregnant. Unfortunately I had a bad tube and a good one and the egg went for the bad one and I ended up in emergency surgery after it ruptured, but I now have hope that I can do it again and this time there is only the good tube to go through.
by Angelina40 11th Mar 2009, 9:17am
Hello, I started my period Jan. 25, 2009, when will I ovulate.
by MandyJ1 28th Jan 2009, 9:03am
hi everyone i think im pregnant but i came on my period could i still take a test
by mzricko 28th Jan 2009, 9:02am
hi everyone, my last period was on 26th dec 08. me an my partner had sex on the 5th an 7th an then the 14th jan, is there a chance i could be pregnant? my period are always on time an last for 28 days, i've been trying for a while now an i feel like we are just not gettin it rite, could u help us pls. thanks
by 3bs 23rd Jan 2009, 8:50am
Can anyone help??!! I finished my pill aug 31st and got my 1st period 3rd of sep and it finished 6th sep, then my next period didnt come till 29th oct (54 days later) and it finished 3rd of november. Now (32 days) later my period still hasent come! I have been having regular sex with my hubby, but i didnt have a clue when i was ovulating. I took a preg test this morning and it came up Neg!! Could i be preg?? Or is my body just F***ed up!! I have been getting the odd tingle in my nipples and a few pains in my womb and discharge like a clear snail trail (yuck) i know!! I AM SO CONFUSED!!! This never happened when i tried with my first child!!Can anyone help????xx
by roobaby 5th Dec 2008, 9:33am
by karamel89 4th Dec 2008, 8:48am
I just started my period yesterday(10/11) when will i ovulate? Please help
by megadz 11th Nov 2008, 9:52am
I have never had regular periods. Can I still get pregnant? I might have 3 a year.
by michellebelle 6th Nov 2008, 8:55am
my periods have also been irregular since June 18 days exactly go by then my period starts for 4 days then 18 days go by again then my period for 4 days. my last period was 17th aug and was very light.
I have no idea now when to test to see if i could be pregnant.
by peanut33 3rd Sep 2008, 9:25am
I started my period on April 6th,2008 (sunday) when will i ovulate next?
by adrianna 7th Apr 2008, 2:44pm
how do i count and know when i am most fertile pls assist me
by ifedi 13th Aug 2007, 2:55pm
I have irregular periods due to having adhesions 2 years ago. My husband & I are trying for a baby but as I do not know my cycle length, Im unsure when I will ovulate. Hence I do not know the best time for intercourse.
by COCO7 6th Aug 2007, 7:54am