The most significant factor affecting female fertility is age.
Smoking and high alcohol consumption decrease both female and male fertility.
Some medicines, such as NSAIDs, may have a negative effect on ovulation and embryo implantation.
Irregular or shortened menstrual cycles or severe menstrual pain may be signs of decreased fertility.
General remarks
A woman or a couple may ask a doctor to assess their fertility. Even before any actual attempt to conceive, women often wonder about their chances of becoming spontaneously pregnant. This is a good opportunity for the doctor to discuss healthy living habits and other factors that might facilitate becoming pregnant.
About 10% of couples will not conceive within a year from starting such attempts. Population level studies have shown that of couples not conceiving within one year, 30-60% will conceive naturally within the next year.
A referral for investigations and treatment of infertility can be written after one year of attempting to conceive, as soon as basic investigations have been performed in primary care; see article Infertility Infertility.
Specific policies and restricions concerning, for example, the age of people seeking such services, may apply in different countries. Find out about local policies and practices..
The fertility rate of women below 30 years has declined in Europe since 2001, whereas the rate of women aged 30 or more has increased (including women older than 35).
An equivalent trend can be seen in men; men become fathers later than before.
In the EU, the total fertility rate was 1.53 live births per woman in 2021 (lowest in Malta, 1.13 and highest in France, 1.84).
Age is the most important factor affecting female fertility.
The most fertile age is between 20 and 25 years.
Fertility begins to decline after the age of 30, and declines strongly from the age of 35.
A higher age means that, in addition to the biological ageing process, the person will also have had longer exposure to factors such as stress, underlying diseases and environmental factors.
With age, the quality of the egg cells deteriorates, increasing miscarriage and foetal chromosomal defects.
In men, ageing lengthens the time to conception and decreases the possibility of pregnancy but it is difficult to define any clear age limit.
Effect of living habits on fertility
Overweight may be associated with ovulation problems, and it also increases the risk of miscarriage.
Underweight women may have menstrual disturbances and ovulation problems.
Obesity impairs the quality of semen.
Smoking shortens the fertile period and brings forward the age at menopause by an average of 2 years. Smoking impairs the quality of semen.
Moderate alcohol consumption has no significant effect on fertility but total abstinence is recommended during conception and pregnancy.
High daily alcohol consumption may disturb sperm production.
NSAIDs may have a negative impact on ovulation and embryo implantation.
Certain drugs, such as testosterone treatment, cytostatic drugs, calcium channel blockers and long-acting sulfa drugs, may disturb sperm production.
Anabolic steroids reduce sperm production in most men and may lead to complete azoospermia.
Certain drugs are harmful to the foetus and should be discontinued well (several months) before planning pregnancy.
Examples of such drugs include isotretinoin, methotrexate, leflunomide, valproate, mycophenolic acid, ribavirin, many cancer drugs and thalidomide.
All women planning to become pregnant are recommended a varied diet supplemented by vitamin D, 10 µg/day, and folic acid, 0.4 mg/day, no later than 2 months before stopping the use of contraception.
Chlamydia in the patient history may have caused ovarian adhesions and thereby ovarian infertility. The risk is significantly increased if there have been several chlamydial infections Chlamydial Urethritis and Cervicitis.
Polycystic ovaries (PCOS Polycystic Ovary Syndrome (PCOS)) may cause disturbances in the menstrual cycle and ovulation. The primary treatment in women with overweight is weight loss.
Severe menstrual pain and/or endometriosis in the family often suggest a risk of endometriosis Endometriosis.
Menstrual cycles becoming clearly shorter than 28 days may signify a reduced ovarian reserve.
About 1% of women enter menopause before the age of 40 years (premature ovarian insufficiency, POI). The risk of POI is about five-fold in near relatives of women with POI.
The doctor may guide the patient towards healthy living habits and awareness of the most fertile time during the menstrual cycle.
To optimize the chance of pregnancy, attempts to conceive should be made 2 to 3 times a week from the end of menstruation until the middle of the menstrual cycle.
Serum AMH (anti-Müller hormone) levels reflect a woman's ovarian reserve but do not really show how fertile she is.
In women below the age of 25, AMH is not reliable in evaluating the ovarian status.
It should primarily be used in the planning of assisted reproduction treatment.
References
Gnoth C, Godehardt E, Frank-Herrmann P et al. Definition and prevalence of subfertility and infertility. Hum Reprod 2005;20(5):1144-7. [PubMed]
Wang X, Chen C, Wang L et al. Conception, early pregnancy loss, and time to clinical pregnancy: a population-based prospective study. Fertil Steril 2003;79(3):577-84. [PubMed]
te Velde ER, Pearson PL. The variability of female reproductive ageing. Hum Reprod Update 2002;8(2):141-54. [PubMed]
Sharma R, Agarwal A, Rohra VK et al. Effects of increased paternal age on sperm quality, reproductive outcome and associated epigenetic risks to offspring. Reprod Biol Endocrinol 2015;13():35. [PubMed]
Silvén H, Savukoski SM, Pesonen P et al. Incidence and familial risk of premature ovarian insufficiency in the Finnish female population. Hum Reprod 2022;37(5):1030-1036. [PubMed]