If you've found yourself here, chances are you've been quietly searching for answers — maybe late at night, maybe after another tough month. We want you to know something right away: looking into the causes of infertility is one of the bravest, most empowering things you can do for yourself. You're not alone in this. Infertility affects about 10-15% of couples, and roughly a third of the time the contributing factors sit on the female side of the equation with female infertility.1 And here's what we really want you to hear: your body isn't working against you. Most causes of infertility are well understood by science, and most of them have real, evidence-based paths forward. In this article, we'll walk through the key causes together — honestly, clearly, and always with hope. Because understanding what's happening is the first step toward changing your story.
First Off, What Even Counts as Infertility?
Before we get into the "why," let's start with what infertility actually means in medical terms. Doctors define it as not conceiving after a year of trying (or six months if you're over 35). We know that word can feel heavy, but it's really important to remember: a diagnosis of infertility isn't a final answer. It's a starting point — the beginning of figuring out what's going on and what can be done about it. According to the World Health Organisation, issues in the ovaries, uterus, fallopian tubes, or endocrine system are the most common underlying factors in infertility.2 In other words, these are areas your doctor can investigate — and in many cases, treat.
How Do Hormonal Imbalances Disrupt Female Fertility?
We hear from so many women in our community who've been told "it's hormonal" without really understanding what that means — so let's unpack it together. Ovulation, the monthly release of an egg, depends on a careful balance of hormones. When that balance is off, conceiving becomes much harder. Ovulatory disorders account for approximately 25–40% of female infertility cases, often linked to imbalances in luteinizing hormone (LH) or follicle-stimulating hormone (FSH) as noted in ovulation tracking research.3 Polycystic ovary syndrome (PCOS) is one of the most common hormonal causes, affecting up to 10% of women with its combination of irregular periods, excess androgens, and insulin resistance according to PCOS and fertility guidelines.4 If you've been diagnosed with PCOS, please know you're in very good company — and there are well-established ways to manage it.
There are also conditions like hypothyroidism or hyperprolactinemia that can quietly interfere with thyroid or prolactin levels and disrupt ovulation, as outlined in clinical reviews of causes of infertility in women.6 A comprehensive review identifies these hormonal factors, including premature ovarian insufficiency, as primary risk factors for female infertility.6 The reassuring part? Medications like clomiphene can effectively restart ovulation in many cases, and the success rates you'll see in the data are genuinely encouraging according to fertility treatments data.3
How Do Structural Issues Affect Female Fertility?
This is another area where many women feel frustrated, because structural issues are often invisible until you start investigating. Your fallopian tubes are the pathway where egg and sperm meet — and when infections, scarring, or pelvic inflammatory disease (PID) block them, that meeting simply can't happen. Research on blocked fallopian tubes shows this is a leading cause, often stemming from untreated STIs.7 Uterine fibroids or polyps can also interfere with implantation, and uterine abnormalities like a septate uterus can play a role as well, as documented in clinical reviews of female infertility.6
Endometriosis deserves special attention here. This condition, where tissue similar to the uterine lining grows outside the womb, affects 25–50% of women experiencing infertility, causing inflammation and adhesions as described in endometriosis and pregnancy research.9 If you're living with endo, we know how exhausting and isolating it can feel — and we want you to know that your experience is valid. Clinical reviews also identify tubal damage and uterine issues as frequent contributing factors in tubal factor infertility.1 Here's what gives us hope if you're facing this: surgery or IVF often successfully bypasses these barriers, and many women go on to conceive according to IVF process and success rates data.3
Which Lifestyle Habits Can Harm Female Fertility?
We want to approach this section gently, because we know how easy it is to start blaming yourself when you read about lifestyle factors. Please don't. The truth is, some of these factors are things you can genuinely influence, and that's actually empowering — see our guide to fertility-supporting exercises for practical ideas. Smoking, for instance, has been shown to damage eggs and accelerate ovarian aging — research consistently shows smoking meaningfully reduces conception chances and is associated with earlier menopause.2 Being significantly over or underweight can also disrupt hormonal balance and ovulation, as noted in weight and fertility research.4 Excessive alcohol, high caffeine intake, or very intense exercise can also have an impact, as outlined in lifestyle factors affecting fertility guidance.2
Environmental toxins like pesticides and plastics — known as endocrine disruptors — are increasingly recognised as contributing factors, according to a meta-analysis of risk factors for environmental toxins fertility.6 And then there's stress, which can raise cortisol levels and potentially delay ovulation — something many of you will understand all too well from the emotional weight of this journey, as explored in research on stress and infertility.5 Here's what we find genuinely encouraging: making lifestyle changes can meaningfully improve fertility. Research suggests that addressing modifiable factors can meaningfully improve fertility outcomes for many couples.2
How Does Age Affect Female Fertility?
We know this is a topic that can bring up a lot of anxiety, so let's talk about it honestly but without the scare tactics. Turning 35 doesn't flip a switch, but your fertility does gradually decline as egg quantity and quality decrease, which can also raise miscarriage risks as documented in getting pregnant after 35 research.1 By 40, your conception chances are roughly half of what they were in your 20s according to age-related fertility decline data.3 Those are the honest numbers — but they're not the whole picture. Options like egg freezing, IVF, and donor eggs have genuinely transformed what's possible for women navigating "advanced maternal age," as discussed in egg freezing and fertility preservation research.8 Many women in their late 30s and early 40s go on to have healthy pregnancies, and we see that in our community every day.
What Is Unexplained Infertility?
This might be one of the most emotionally difficult diagnoses to hear. When all your tests come back normal and there's no clear explanation, it's natural to feel lost. Unexplained infertility affects 10-30% of couples, according to unexplained infertility research.7 The underlying cause may involve subtle immune factors, genetic variations, or even metabolic conditions complicating things in ways current tests can't fully detect, as explored in clinical reviews of female infertility.6 We know how frustrating that uncertainty feels. But here's what's worth holding onto: treatments like timed intercourse or IUI often work even without a specific diagnosis, as noted in clinical practice guidelines.7 Many couples with unexplained infertility do go on to conceive — and you may well be one of them.
| Cause | Estimated Prevalence | Primary Mechanism | Common Treatment Approaches |
|---|---|---|---|
| Ovulatory disorders (PCOS, hypothalamic amenorrhea) | 25–40% of cases | Disrupted hormonal signalling prevents regular ovulation | Lifestyle changes, ovulation induction medications, inositol supplementation |
| Endometriosis | 25–50% of infertile women | Inflammatory tissue growth impairs egg quality, implantation, and tubal function | Laparoscopic surgery, hormonal therapy, IVF, anti-inflammatory support |
| Tubal factor (blocked or damaged fallopian tubes) | 25–35% of cases | Physical blockage prevents egg–sperm meeting or embryo transport | Surgical repair, IVF (bypasses tubes entirely) |
| Uterine fibroids or polyps | 5–10% of cases | Growths distort uterine cavity, interfering with implantation | Hysteroscopic removal, myomectomy, medication |
| Age-related decline | Accelerates after 35 | Diminished ovarian reserve and increased chromosomal abnormalities in eggs | Egg freezing, IVF with PGT, donor eggs, CoQ10 and antioxidant support |
| Unexplained infertility | 10–30% of cases | No identifiable cause found through standard testing | IUI, IVF, lifestyle optimisation, nutritional supplementation |
| Lifestyle factors (weight, stress, toxins) | Contributory in many cases | Hormonal disruption, oxidative stress, inflammation from modifiable habits | Diet and exercise changes, stress management, reducing toxin exposure |
When Should You Get Checked for Infertility?
If you're wondering whether it's time to see a specialist, trust that instinct. The process usually starts with straightforward steps: tracking your cycles, blood tests to check your hormone levels, and ultrasounds to look for conditions like PCOS or cysts as described in PCOS diagnosis guidelines.4 From there, your doctor might recommend an HSG (a dye test to check your tubes) or laparoscopy to look for endometriosis, as outlined in fertility evaluation guidelines.3 We won't pretend the process is easy emotionally — it can be genuinely tough. If you're feeling overwhelmed, that's completely normal, and reaching out to a support group or therapist can make a real difference. Research confirms that infertility's psychological toll is significant and that emotional support matters, as explored in infertility emotional support studies.5
When it comes to treatment, there are more options available today than ever before — from ovulation medications to surgical correction to IVF, as documented in IVF success rates data.3 A global study notes that when you have access to appropriate care, outcomes improve dramatically according to global infertility statistics.1 And if you're dealing with secondary infertility — difficulty conceiving after a previous pregnancy — know that factors like adhesions or age-related changes may be involved, but success rates remain high with proper support as noted in secondary infertility causes research.6
What Should You Do Next If You Suspect Infertility?
If there's one thing we hope you take away from this article, it's that infertility is not a dead end — it's a chapter, not the whole story. Whether you're navigating PCOS, structural challenges, or lifestyle factors that need attention, most causes of female infertility (ovulatory and ovarian disorders account for approximately 25–40%) have well-established treatment pathways, as documented in fertility evaluation guidelines.3 Be kind to yourself through this process, lean on the people who care about you, and remember: millions of women find their way through this every year — and you can too. Supporting your fertility involves multiple factors — medical evaluation, lifestyle optimisation, and nutritional support. If you're interested in exploring a comprehensive approach to preconception nutrition, our range of research-informed fertility supplements is formulated with the nutrients discussed in this guide.
Frequently Asked Questions About Female Infertility
What are the most common causes of infertility in women?
The most common causes include ovulatory disorders (such as PCOS and hypothalamic dysfunction), blocked or damaged fallopian tubes, endometriosis, uterine abnormalities (such as fibroids or polyps), and age-related decline in egg quality and quantity. In some cases, no identifiable cause is found — this is known as unexplained infertility. A thorough evaluation by a reproductive specialist can help identify your underlying issue and guide treatment.
Can endometriosis cause infertility?
Yes. Endometriosis affects approximately 25–50% of women with fertility difficulties. The condition causes tissue similar to the uterine lining to grow outside the uterus, which can lead to scarring, blocked fallopian tubes, inflammation, and impaired egg quality. However, many women with endometriosis do conceive naturally or with medical assistance. Early diagnosis and appropriate management can significantly improve your fertility outcomes.
At what age does female fertility start to decline?
Female fertility begins a gradual decline from the late 20s, with a more noticeable drop after age 35. By 40, both the quantity and quality of your eggs decline considerably, making conception harder and increasing the risk of chromosomal abnormalities. This is due to the natural depletion of the ovarian reserve — you're born with all the eggs you'll ever have. While age is an important factor, many women in their late 30s and early 40s do conceive successfully, particularly with appropriate support.
Can stress cause infertility in women?
Chronic high stress can interfere with fertility by elevating cortisol levels, which may suppress the hormones (GnRH, LH, and FSH) needed to trigger ovulation. This can lead to irregular cycles or anovulation. While stress alone is rarely the sole cause of infertility, reducing stress through mindfulness, gentle exercise, therapy, or adequate rest can support your overall hormonal balance and emotional wellbeing during the conception journey.
Is unexplained infertility common?
Unexplained infertility is diagnosed in approximately 10–30% of couples undergoing fertility evaluations when standard tests return normal results for both partners. It doesn't mean nothing is wrong — it may indicate subtle issues with egg or sperm quality, fertilisation, or implantation that current diagnostic tools can't detect. Many couples with unexplained infertility do go on to conceive, either naturally over time or with treatments such as IUI, IVF, or targeted supplementation.
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.
References
- Carson SA, Kallen AN. Diagnosis and management of infertility: a review. JAMA. 2021;326(1):65-76. doi:10.1001/jama.2021.4788
- World Health Organisation. Infertility fact sheet. WHO. Updated April 2023. www.who.int/news-room/fact-sheets/detail/infertility
- Practice Committee of the American Society for Reproductive Medicine. Evidence-based treatments for couples with unexplained infertility: an ASRM guideline. Fertility and Sterility. 2020;113(2):305-322. doi:10.1016/j.fertnstert.2019.10.014 [Note: Updated from 2015 edition; supersedes previous ASRM diagnostic evaluation committee opinion.]
- Teede HJ, Misso ML, Costello MF, et al. Recommendations from the international evidence-based guideline for the assessment and management of polycystic ovary syndrome. Fertility and Sterility. 2018;110(3):364-379. doi:10.1016/j.fertnstert.2018.05.004
- Rooney KL, Domar AD. The relationship between stress and infertility. Dialogues in Clinical Neuroscience. 2018;20(1):41-47. doi:10.31887/DCNS.2018.20.1/klrooney
- Walker MH, Tobler KJ. Female infertility. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2024. www.ncbi.nlm.nih.gov/books/NBK556033/
- Lindsay TJ, Vitrikas KR. Evaluation and treatment of infertility. American Family Physician. 2015;91(5):308-314. PMID: 25751033
- Dunson DB, Colombo B, Baird DD. Changes with age in the level and duration of fertility in the menstrual cycle. Human Reproduction. 2002;17(5):1399-1403. doi:10.1093/humrep/17.5.1399
- Bulletti C, Coccia ME, Battistoni S, Borini A. Endometriosis and infertility. Journal of Assisted Reproduction and Genetics. 2010;27(8):441-447. doi:10.1007/s10815-010-9436-1
Marina Carter
Fertility Health Writer at FertilitySmart
Marina Carter is a specialist health writer with nearly a decade of experience in reproductive health, fertility nutrition, and evidence-based conception support. She has authored over 30 in-depth articles for FertilitySmart, translating peer-reviewed research into clear, practical guidance to support you and your partner on your fertility journey. Read full bio →