How Long Is Normal?
Before assuming something is wrong, it helps to understand realistic conception timelines. In couples having regular unprotected intercourse, approximately 85% will conceive within one year and 92% within two years. In any given cycle, even in perfectly fertile couples in their mid-twenties, the chance of conceiving is only 20–25%. Biology is not an instant process. This context matters — it prevents both premature panic and, equally important, dangerous complacency.
The clinical threshold for investigation is 12 months of trying without success in women under 35, and 6 months in women 35 and over. These are not arbitrary numbers — they reflect how quickly age erodes fertility and the value of intervening before conditions worsen. If there is any known reason to suspect a problem (irregular periods, previous pelvic infections, known male factor issues), earlier evaluation is always appropriate.
Ovulation Problems: The Most Common Female Factor
Ovulation problems account for roughly 25–30% of all infertility cases. Without ovulation, there is no egg to fertilise. The most common cause of ovulatory dysfunction in women of reproductive age is PCOS (polycystic ovary syndrome), but other causes include thyroid disorders (both underactive and overactive thyroid suppress normal ovulation), hyperprolactinaemia (elevated prolactin from a pituitary microadenoma or medication side effect), premature ovarian insufficiency, and hypothalamic dysfunction from extreme exercise, very low body weight, or severe caloric restriction.
Identifying whether ovulation is occurring is straightforward: a progesterone blood test on day 21 of a standard cycle (or 7 days after suspected ovulation) confirms it. A level above 30 nmol/L indicates ovulation occurred. If cycles are irregular, ovulation tracking with basal body temperature and ovulation predictor kits can help identify if and when ovulation is happening.
Tubal Factor: Blocked or Damaged Fallopian Tubes
The fallopian tubes carry the egg from the ovary to the uterus and are where fertilisation occurs. Blocked or damaged tubes prevent the egg and sperm from meeting. Tubal damage is most commonly caused by previous pelvic inflammatory disease (PID) — often from untreated chlamydia or gonorrhoea — previous abdominal or pelvic surgery, endometriosis, or a previous ectopic pregnancy. A hydrosalpinx (a tube filled with fluid due to blockage) is particularly damaging to IVF success rates because the fluid leaks into the uterine cavity and impairs implantation.
Tubal status is assessed by hysterosalpingography (HSG) — an X-ray procedure where dye is passed through the tubes — or by laparoscopy, which allows direct visual assessment. Many women with tubal factor infertility have no symptoms and no history that would suggest it; the first discovery is at investigation.
Male Factor: Responsible for Nearly Half of All Cases
This is the most important point to emphasise because it is the most underestimated. Male factor issues contribute to infertility in approximately 40–50% of couples who struggle to conceive, either as the sole cause or a contributing factor. Despite this, the male partner is frequently not investigated until months or years after the woman has undergone extensive testing.
A semen analysis — the first investigation for male fertility — is a simple, non-invasive test that provides comprehensive information about sperm concentration, motility (movement), morphology (shape), and volume. It should be one of the first investigations performed in any couple having difficulty conceiving, not an afterthought after the female partner has been fully worked up. Common causes of male factor infertility include varicocele (enlarged veins in the scrotum that raise testicular temperature), previous infections (mumps orchitis, STIs), hormonal imbalances, genetic causes, lifestyle factors (smoking, anabolic steroids, heat exposure, obesity), and obstructive causes from previous surgery.
Endometriosis
Endometriosis — where tissue similar to the uterine lining grows outside the uterus — affects roughly 10% of women of reproductive age and is diagnosed in approximately 25–50% of women investigated for infertility. It impairs fertility through multiple mechanisms: physical distortion of pelvic anatomy, inflammation that damages eggs and sperm, adhesions that block tubes, and an altered endometrial environment that impairs implantation. Endometriosis is notoriously underdiagnosed — the average time from first symptoms to diagnosis is 7–10 years in many healthcare systems. Symptoms include painful periods, deep pain during intercourse, pelvic pain at other times in the cycle, and bowel symptoms. Definitive diagnosis requires laparoscopy.
Uterine Problems
The uterine cavity — where the embryo implants and grows — can be disrupted by fibroids (benign muscle tumours), polyps (small growths of endometrial tissue), a septum (a piece of tissue dividing the cavity), or adhesions (scar tissue from previous surgery or infection). Submucosal fibroids and polyps that distort the cavity are the most likely to impair implantation and increase miscarriage risk. Assessment of the uterine cavity is performed by hysteroscopy (a camera passed through the cervix into the cavity) or saline-infusion sonography.
Unexplained Infertility
After standard investigation, approximately 10–15% of couples are given a diagnosis of unexplained infertility — all standard tests are normal but conception has not occurred. This is a frustrating diagnosis but it is not hopeless. It means either that the cause is subtle enough to be missed by standard tests, or that the couple is simply at the lower end of normal fertility requiring more time or mild intervention to succeed. Treatments including ovulation induction with intrauterine insemination (IUI) or IVF are effective in this group and are usually offered after 1–2 years of unexplained infertility.
Age and Egg Quality
Female age is the most powerful single determinant of natural fertility and IVF success. Egg quality — specifically the proportion of chromosomally normal eggs — declines significantly from the mid-thirties. At 25, roughly 75–80% of eggs are chromosomally normal. By 40, only 10–20% are. This is why miscarriage rates increase and live birth rates from IVF fall steeply with age, and why timing matters enormously in the decision to seek help.
What to Do Next
The single most useful step for any couple who has been trying for 6–12 months without success is to seek a basic fertility evaluation simultaneously for both partners. In women: a cycle day 2–3 blood test (FSH, LH, oestradiol), AMH, progesterone on day 21, thyroid function, pelvic ultrasound with antral follicle count, and tubal assessment if indicated. In men: a semen analysis. These tests together identify the cause in the majority of couples and allow a targeted treatment plan to be formed. Waiting another 12 months to see if things improve without investigation is rarely the right decision, particularly in women over 35.