Pu­blished: 8. Fe­bruary 2022 | Up­dated: 25. Au­gust 2023 Author: Jo­hanna Kohnen | Re­viewed by Jo­hanna Kohnen

Un­der­stan­ding your mens­trual cycle

The first step: get­ting to know your own cycle

Not every woman has a per­fect 28-day cycle: in rea­lity, it usually va­ries bet­ween 21 and 35 days. But larger fluc­tua­tions are not un­common either: Stu­dies have shown that 46% of all women have cycle fluc­tua­tions of more than 7 days; 20% of all women even have fluc­tua­tions of more than 14 days [1]. If you have cycle fluc­tua­tions that go beyond the 21- or 35-day limit, it is ad­vi­sable to con­sult a gy­nae­co­lo­gist in the con­text of wan­ting a child.

Be­cause: There are only a few days per month where you can get pregnant. The time window for fer­ti­li­sa­tion of the egg is 12 to 18 hours after ovu­la­tion. So if you want to have a baby, it’s worth re­cor­ding your own cycle and get­ting to know it better. In ad­di­tion to the pos­si­bi­lity of en­te­ring the data in a pe­riod ca­lendar, there are also va­rious apps that make this pos­sible.

But even if you de­ter­mine your fer­tile days cor­rectly, you are he­althy and have sex at the op­timal time: The average chance of pregnancy per mens­trual cycle is only 25% [2].

In ad­di­tion, va­rious stu­dies have shown that half of all cou­ples who want to have children do not know the time frame of the most fer­tile days, which fur­ther re­duces this chance [3].

Ovu­la­tion, also called ovu­la­tion, oc­curs about 12 to 16 days be­fore mens­trua­tion in most women. The pe­riod bet­ween ovu­la­tion and mens­trua­tion is fairly con­stant for most women. Fluc­tua­tions in the cycle are usually due to de­layed or ac­ce­le­rated ovu­la­tion, which can often have psy­cho­lo­gical causes: Stress at work or in ever­yday life, long-di­stance travel with time ch­anges, or strong emo­tional fluc­tua­tions. Ul­ti­m­ately, the better you know your cycle and learn to per­ceive your body si­gnals, the more in­fluence you can have on your fer­ti­lity.

De­ter­mi­ning fer­tile days

A po­pular me­thod of de­ter­mi­ning a wo­man’s fer­tile pe­riod is the so-called tem­pe­ra­ture me­a­su­re­ment me­thod. The woman me­a­sures her body tem­pe­ra­ture with a ther­mo­meter and re­cords it. This pro­duces a so-called basal curve, which can in­di­cate the ideal time for con­cep­tion. This time is exactly be­fore the rise in basal body tem­pe­ra­ture. In the be­gin­ning, this me­thod may re­quire one or two prac­tice cy­cles in order to be­come fa­mi­liar with the hand­ling and in­ter­pre­ta­tion of the va­lues.

You can also de­ter­mine your fer­tile time with the help of ovu­la­tion tests, which are now available in drugs­tores, phar­macies and on­line. They me­a­sure the in­crease in lut­ei­ni­sing hor­mone (LH) in your urine using a test stick, si­milar to a pregnancy test. As this hor­mone ch­ange oc­curs bet­ween 24 and 36 hours be­fore ovu­la­tion, a ri­sing LH level shows you that your fer­tile days are ap­proa­ching.

A third me­thod is to ob­serve the cer­vical mucus and pal­pate the cervix. The cer­vical mucus is a se­cre­tion that is pro­duced by glands in the cervix and ch­anges in con­sis­tency du­ring the cycle. This means that con­clu­sions can be drawn about the re­spec­tive phase of the cycle from its ch­anges. For ex­ample, shortly be­fore ovu­la­tion it is more glassy, trans­pa­rent and thin. This helps the sperm to reach the uterus more quickly and ea­sily.

Understanding your menstrual cycle


It’s not unu­sual for cou­ples to take up to a year

But get­ting pregnant is not that easy. A study shows that in Ger­many, of all women who know their cycle and want to get pregnant, only about half get pregnant du­ring the first 3 months. After 6 months, about 65% of cou­ples have suc­ceeded, and after a year, about 80%. For cou­ples who try for 2 years, the rate rises to 89% [4].

The li­keli­hood of pregnancy also de­pends to a large extent on the age of the woman. In ge­neral, younger women get pregnant faster than older women be­cause hor­mone pro­duc­tion and egg re­serve de­crease with age. So de­pen­ding on your age, it can be per­fectly normal for con­cep­tion to take up to a year. Ho­wever, if you have been trying un­suc­cessfully for more than a year, it is ad­vi­sable to seek me­dical help.

About Fer­tilly

At Fer­tilly, we have made it our mis­sion to ac­com­pany cou­ples (ho­mo­se­xual and he­te­ro­se­xual) and sin­gles on the way to ful­fil­ling their child wish. In doing so, it is im­portant to us to create trans­pa­rency in the area of fer­ti­lity ser­vices, to pro­vide in­for­ma­tion and know­ledge on the to­pics of pregnancy and fer­ti­lity and to help you to find the most sui­table Fer­ti­lity Center. Th­rough co­ope­ra­tion with first-class Fer­ti­lity Cen­tres and cli­nics in Eu­rope, en­qui­ries about Fer­tilly are given pre­fe­ren­tial tre­at­ment. This means that our pa­ti­ents avoid the usually long wai­ting times and get ap­point­ments more quickly.

If you would like more in­for­ma­tion about Fer­ti­lity Cen­ters, suc­cess rates and prices, please contact us using this ques­ti­on­n­aire. We will ad­vise you free of charge and wi­t­hout any ob­li­ga­tion.

  • Answer the first ques­tions in the on­line form in order to book an ap­point­ment. This way we can better ad­dress your needs du­ring the con­ver­sa­tion.

  • We will find the best contact person for your in­di­vi­dual needs. Sche­dule 20 mi­nutes for the con­sul­ta­tion.

  • We will in­tro­duce you to the right fer­ti­lity clinic from our net­work, make an ap­point­ment and ac­com­pany you until your wish for a child is ful­filled.

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1. Creinin, Ke­ver­line & Meyn. How re­gular is re­gular? An ana­lysis of mens­trual cycle re­gu­la­rity. Con­tracep­tion (2004) 70:289–92
2. Co­lombo & Ma­sarotto. Daily Fecundability: First Re­sults from a New Data Base. De­mo­gra­phic Re­se­arch (2000)
3. Johnson SR., et al. Human Re­pro­duc­tion (2011) 26: i236.
4. Juul, Kar­maus & Olsen. Re­gional dif­fe­rences in wai­ting time to pregnancy: pregnancy-based sur­veys from Den­mark, France, Ger­many, Italy and Sweden. Human Re­pro­duc­tion (1999), 14: 1250–1254