When pregnancy takes longer than expected, women are often blamed first. That assumption is medically wrong and can delay the right diagnosis. Infertility can involve male factors, female factors, a combination of both, or factors that remain unexplained after standard evaluation.
The World Health Organization defines infertility as failure to achieve a pregnancy after 12 months or more of regular unprotected sexual intercourse and estimates that about one in six people of reproductive age experience infertility in their lifetime. Its 2025 guidance stresses care for male, female and unexplained infertility. Read the WHO infertility fact sheet.
When should a couple seek an infertility assessment?
In general, assessment is recommended after 12 months of regular unprotected sex without pregnancy. It should begin sooner when the woman is 35 or older, and promptly when she is over 40. Earlier evaluation is also sensible when there are irregular or absent periods, a history of pelvic infection or cancer treatment, known endometriosis, previous ectopic pregnancy, repeated pregnancy loss, sexual or ejaculation difficulties, testicular problems, or another known fertility risk.
Both partners should be evaluated concurrently. The AUA and ASRM guideline specifically recommends assessment of male and female partners at the same time. Starting with only the woman can waste months and place unfair pressure on one person.
Common female causes of infertility
Ovulation disorders
Pregnancy requires the release of an egg. Irregular or absent ovulation can be associated with polycystic ovary syndrome, thyroid disorders, elevated prolactin, major weight changes, very intense exercise, diminished ovarian function and other hormonal conditions.
PMOS/PCOS is a common cause of anovulation, but having polycystic-looking ovaries on a scan is not enough on its own to diagnose the syndrome. Treatment depends on symptoms, metabolic health and pregnancy goals. Nordica’s guide to PCOS and fertility explains the condition in more detail.
Blocked or damaged fallopian tubes
The fallopian tubes are where egg and sperm normally meet. Damage or blockage can follow pelvic inflammatory disease, some sexually transmitted infections, previous pelvic surgery, endometriosis or a previous ectopic pregnancy. IVF can bypass the tubes when they are severely damaged or blocked.
Tubal disease is especially relevant in Nigeria. A 2015 to 2023 cohort of 236 couples at Lagos University Teaching Hospital found tubal pathology was common among the women in that specific assisted-conception population. The study does not represent every Nigerian couple, but it supports careful attention to infection history and tubal assessment. Read the Lagos infertility-pattern study and Nordica’s article on pelvic inflammatory disease and infertility.
Endometriosis
Endometriosis occurs when tissue similar to the lining of the womb grows outside the uterus. It may cause severe period pain, pain during sex, pelvic pain or no obvious symptoms. It can affect fertility through inflammation, scarring, ovarian cysts and distortion of pelvic anatomy. The best treatment depends on age, pain, ovarian reserve, disease extent and previous surgery.
Uterine or cervical conditions
Fibroids, endometrial polyps, adhesions and congenital differences in the shape of the uterus can interfere with implantation or pregnancy in some patients. Not every fibroid causes infertility. Size, number and, most importantly, whether a fibroid distorts the uterine cavity help determine relevance. Nordica’s article on uterine fibroids and fertility provides a fuller explanation.
Cervical factors are a less common isolated explanation, but cervical surgery, scarring or mucus problems may occasionally affect sperm passage.
Age-related decline and diminished ovarian reserve
Age affects both egg number and egg quality. Diminished ovarian reserve means the remaining egg supply is lower than expected for age or that response to stimulation may be reduced. It does not mean that every remaining egg is abnormal or that pregnancy is impossible. Nordica’s article on age and fertility in women explains why timely evaluation matters.
Primary ovarian insufficiency
Primary ovarian insufficiency occurs when ovarian function declines before age 40. Periods may become irregular or stop, although ovarian activity can sometimes occur intermittently. Causes may be genetic, autoimmune, treatment-related or unknown. Fertility options require specialist review.
Common male causes of infertility
Male infertility may involve sperm production, sperm function, the pathway that carries sperm, ejaculation, hormones or sexual function. It often has no obvious outward symptom.
Low sperm concentration or no sperm in the ejaculate
Oligozoospermia means a low sperm concentration. Azoospermia means no sperm are seen in the ejaculate. Azoospermia can result from a blockage or from severely reduced sperm production. These situations require different investigations and treatments.
Reduced sperm movement or abnormal morphology
Sperm must move through the reproductive tract and interact with the egg. Reduced motility and a high proportion of abnormal forms can lower the chance of fertilisation, but one semen parameter should not be interpreted in isolation. Semen results vary, and an abnormal test may need to be repeated.
Varicocele
A varicocele is an enlargement of veins around the testicle. It is common and does not cause infertility in every man. Treatment may be considered when a man has a palpable varicocele, infertility and abnormal semen parameters, after proper specialist assessment.
Hormonal, genetic or testicular conditions
Disorders affecting the hypothalamus, pituitary gland or testes can reduce sperm production. Undescended testes, testicular injury, infection, chemotherapy, radiotherapy and some genetic conditions may also contribute. Severe sperm abnormalities sometimes require hormone or genetic testing.
Blockage and ejaculation problems
Sperm may be produced but prevented from reaching the ejaculate because of a blockage in the reproductive tract. Ejaculation difficulties, retrograde ejaculation, erectile dysfunction or spinal and neurological conditions can also affect conception.
Medicines, testosterone and anabolic steroids
Some medicines can affect fertility. Testosterone therapy and anabolic steroids are particularly important because they can suppress the hormonal signals needed for sperm production. Men trying to conceive should not stop prescribed medicine on their own, but they should tell the fertility specialist everything they use.
Lifestyle and environmental factors
Smoking, heavy alcohol use, obesity, excessive heat exposure and some occupational toxins may affect sperm health. These are risk factors, not proof of the only cause. Lifestyle improvement can support health, but it should not replace medical evaluation when semen results are abnormal.
Nordica covers investigations and treatment pathways in male infertility: causes, diagnosis and treatment and its male-factor infertility service.
What is unexplained infertility?
Unexplained infertility does not mean imaginary infertility, and it does not mean that no biological problem exists. It means the standard evaluation has not identified a clear cause.
Before that label is used, assessment usually confirms that ovulation is occurring, at least one fallopian tube appears open, the uterine cavity has been considered and semen analysis does not show a clear male factor. Even then, routine tests cannot measure every step of reproduction. Egg-sperm interaction, subtle sperm function, embryo development and implantation biology may not be fully visible.
Unexplained infertility should therefore be treated as a diagnosis of exclusion. Nordica’s detailed article on unexplained infertility, diagnosis and treatment discusses what may happen next.
Treatment can include a limited period of expectant management, ovarian stimulation with IUI, or IVF, depending on the woman’s age, duration of infertility, previous treatment and preferences. IVF may also reveal information about fertilisation and embryo development, although it does not always identify a single cause.
What tests are commonly used?
Testing should answer a clinical question. A typical starting evaluation may include:
a detailed history for both partners;
confirmation of ovulation where this is uncertain;
pelvic ultrasound;
assessment of ovarian reserve when relevant to treatment planning;
assessment of tubal patency and the uterine cavity;
at least one properly collected semen analysis;
targeted hormone, genetic, infection or imaging tests when indicated.
Not every patient needs every advanced test. Tests marketed after unsuccessful treatment, including some immune panels, sperm DNA tests and endometrial receptivity tests, have varying evidence and should not be ordered simply because they are available.
Matching treatment to the cause
Treatment may involve correcting a hormonal problem, inducing ovulation, surgery for selected anatomical conditions, IUI, IVF, ICSI, sperm retrieval, donor eggs, donor sperm, donor embryos or surrogacy. The correct route depends on the diagnosis and on whether the barrier involves producing eggs or sperm, bringing egg and sperm together, creating embryos, or safely carrying a pregnancy.
This is why diagnosis comes before treatment. IVF is powerful, but it is not the first or only answer for every couple.
Frequently asked questions
Can both partners have fertility problems?
Yes. Combined male and female factors are common. The Lagos cohort cited above found combined factors in a substantial portion of its patients, reinforcing the need to assess both partners.
Can a man with a normal sex drive be infertile?
Yes. Sexual function and sperm quality are related in some cases but are not the same. A man may feel healthy and have no symptoms while semen analysis shows a problem.
Does unexplained infertility mean IVF is the only option?
No. Age, duration and previous treatment matter. Some couples may try expectant management or stimulated IUI, while others may be advised to proceed to IVF sooner.
Can infection cause infertility?
Yes. Some untreated reproductive tract infections can damage the fallopian tubes or male reproductive tract. Prompt testing and treatment can reduce complications, although antibiotics cannot reverse established scarring.
