Author: Dr Irfana Koita | Published: 1 November 2025
Why Am I Not Falling Pregnant? A Fertility Expert Explains
If you have been trying to conceive without success, you are far from alone. Around 1 in 7 couples in the UK experience difficulty getting pregnant, and in approximately 40% of those cases, contributing factors are found in both partners (NICE CG156).
Research on conception probability shows this figure varies by timing within the cycle: the likelihood ranges from approximately 10% when intercourse occurs five days before ovulation up to 33% on the day of ovulation itself (British Columbia Medical Journal).
Key Takeaways
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Around 1 in 7 UK couples experience difficulty conceiving
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Ovulatory disorders, tubal damage, and male factor infertility are the most common causes
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Body weight significantly affects fertility: a BMI of 20 to 25 is optimal for conception
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Start folic acid at least three months before trying to conceive
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Seek specialist referral after 12 months (under 36) or at presentation (36 and over)
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Both partners should be investigated at the same time
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Professional guidance can identify treatable causes that lifestyle changes alone may not address
Common Causes of Infertility in Women
According to NICE clinical guidelines, ovulatory disorders account for approximately 25% of female infertility cases, tubal damage for 20%, uterine or peritoneal conditions for 10%, and unexplained infertility for a further 25%. Male factor infertility contributes to around 30% of all cases, and in 40% of couples, problems are identified in both partners (NICE CG156).
The most common causes of infertility in women include:
Ovulation Disorders
Polycystic ovary syndrome (PCOS) is the most frequent cause of anovulation, affecting an estimated 8 to 13% of women of reproductive age worldwide (WHO). Other ovulatory disorders include hypothalamic dysfunction, premature ovarian insufficiency, and hyperprolactinaemia. If your periods are irregular (shorter than 21 days or longer than 35 days), absent, or very light, this may indicate that ovulation is not occurring regularly.
Tubal and Structural Factors
Blocked or damaged fallopian tubes prevent the egg and sperm from meeting. Common causes include previous pelvic infections such as chlamydia, prior surgery, or endometriosis. Endometriosis, where tissue similar to the womb lining grows outside the uterus, affects approximately 1 in 10 women of reproductive age and can impair egg quality, disrupt ovulation, and reduce implantation success (NHS).
Age-Related Decline
Women are born with a fixed number of eggs, and both egg quantity and quality decline with age. The fall accelerates after 35: approximately 80% of couples under 35 conceive within 12 months of trying, but this drops significantly for women over 40. Age also increases the proportion of chromosomally abnormal eggs, raising miscarriage risk.
Thyroid and Hormonal Imbalances
Both an underactive and overactive thyroid can interfere with ovulation, even when periods appear regular. NICE guidelines recommend thyroid function testing as part of the initial fertility assessment, because thyroid conditions are treatable and correcting them often restores normal ovulation.
Reasons for Not Getting Pregnant: Male Factors
Male factor infertility is one of the leading contributors, affecting approximately 40 to 50% of couples who experience difficulty. Despite this, doctors often investigate male partners later than they should. The World Health Organization's 2021 laboratory manual sets the following lower reference limits for normal semen analysis: sperm concentration of 16 million per mL, total sperm count of 39 million per ejaculate, total motility of 42%, and normal morphology of 4% (WHO Laboratory Manual, 6th edition).
Factors that can reduce sperm quality include:
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Smoking and excessive alcohol consumption
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Elevated scrotal temperature from tight clothing, hot baths, or prolonged laptop use
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Being significantly overweight or underweight
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Certain medications and anabolic steroids
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Previous infections or undescended testes
How to Increase Chances of Getting Pregnant: Evidence-Based Steps
Time Intercourse With Your Fertile Window
The fertile window spans approximately six days: the five days before ovulation and ovulation day itself. Sperm can survive in the reproductive tract for up to five days, so having intercourse every two to three days throughout the cycle is the simplest effective approach. You do not need to time intercourse precisely to ovulation day, though ovulation predictor kits can help identify peak fertility.
Maintain a Healthy Weight
Body weight significantly affects fertility. A study of obese women (BMI 30 or above) found a relative risk of 3.1 for ovulatory dysfunction compared to women with a normal BMI of 20 to 25. Furthermore, a structured six-month lifestyle intervention in obese women led to significantly higher natural conception rates (RR 1.61, 95% CI 1.16 to 2.24) (BCMJ).
Nutrition and Supplements
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Folic acid: 400 micrograms daily, ideally started at least three months before conception. This reduces neural tube defect risk by approximately 70% (USPSTF, JAMA 2023).
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A balanced diet rich in leafy greens, berries, whole grains, lean protein, and healthy fats supports hormonal function
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Omega-3 from oily fish supports egg and sperm quality
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Vitamin D, zinc, and selenium may benefit both partners
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Limit caffeine to 200mg per day (around two cups of coffee)
Exercise Wisely
Moderate exercise supports fertility, but excessive intense exercise can have the opposite effect. In women with a normal BMI, vigorous physical activity of five or more hours per week was associated with a fecundability ratio of 0.58 compared to no vigorous activity, meaning a 42% lower chance of conceiving per cycle. In contrast, overweight women doing the same amount of vigorous exercise had 27% higher fecundability (BCMJ).
Stop Smoking and Limit Alcohol
Smoking affects both egg and sperm quality and is associated with earlier menopause. The NHS advises avoiding alcohol entirely when trying to conceive, as even moderate intake can reduce conception rates.
Not Getting Pregnant After a Year: When to Seek Help
If you are not getting pregnant after a year of regular unprotected intercourse, the updated NICE guideline (NG257) recommends referral for specialist consultation. For women aged 36 and over, NICE recommends referral at presentation, without waiting a full year. Earlier investigation is also recommended if either partner has a known or suspected cause of infertility, such as absent periods, a history of pelvic surgery, previous chemotherapy, or known conditions like endometriosis or PCOS (NICE NG257).
You should also seek earlier advice if you are not getting pregnant after a year and:
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Your periods have become irregular or stopped
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You have experienced recurrent miscarriages
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You or your partner have a known medical condition affecting fertility
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You are over 40, in which case NICE recommends immediate referral
Fertility Tests Before Pregnancy: What to Expect
Fertility tests before pregnancy help identify or rule out common causes of delay so you can make informed decisions. NICE guidelines recommend investigating both partners at the same time, rather than completing one partner's tests before starting the other's.
For Women
Hormone blood tests are typically the first step:
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AMH (Anti-Mullerian Hormone): measures ovarian reserve and can be tested on any day of the cycle
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FSH (Follicle Stimulating Hormone): tested on day 2 to 5 of the cycle; elevated levels may indicate reduced ovarian reserve
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Day 21 progesterone (or 7 days before expected period): confirms whether ovulation occurred that cycle
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Thyroid function and prolactin: both can disrupt ovulation when abnormal
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Rubella immunity: checked to ensure vaccination is up to date before conception
Imaging investigations may include:
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Pelvic ultrasound: checks the ovaries, uterus, and antral follicle count
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HyCoSy: an ultrasound-based test checking whether fallopian tubes are open, available at IVF Matters as an outpatient procedure
For Men
Semen analysis is the primary investigation. A single abnormal result should be repeated after two to three months, as sperm production takes approximately 74 days and results can fluctuate.
How to Increase Chances of Getting Pregnant: A Practical Action Plan
Step 1: Start folic acid and review your lifestyle three months before trying. Address smoking, weight, and any medications with your GP.
Step 2: Have regular intercourse every two to three days throughout your cycle.
Step 3: Track your cycle length and regularity. Note any irregularities to discuss with your GP.
Step 4: If you are under 36 and have been trying for 12 months, or over 36 and trying for 6 months, request a referral for fertility assessment.
Step 5: Consider specialist consultation if initial investigations are normal, but you still aren't conceiving. Advanced testing such as HyCoSy, detailed hormone panels, or sperm DNA fragmentation analysis may identify issues that GP-level tests miss.
Where to Get Support
IVF Matters offers comprehensive fertility assessment and treatment options:
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At-home AMH testing kits
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HyCoSy and pelvic ultrasound scans
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Semen analysis
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Full hormone panels
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Online and in-person consultations with fertility specialists
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Personalised treatment plans including IVF, ICSI, IUI, and egg or sperm freezing
Notably, 12.5% of IVF Matters patients conceive naturally without needing IVF, through appropriate guidance, timing adjustments, and lifestyle optimisation.
Schedule a FREE Advisory Call with Dr Irfana Koita, Fellow of the Royal College of Obstetricians and Gynaecologists, to discuss your individual situation.
Struggling to Conceive? - Next Steps:
