From ovarian reserve to IVF β the biology, the timelines, and the decisions that matter.
Fertility is the area of women's medicine most saturated with misinformation, false reassurance, and unnecessary delay. Most women find out what their fertility actually looks like years too late. Here is what you need to know β and when you need to know it.
Anti-MΓΌllerian Hormone (AMH) is produced by the small antral follicles in the ovaries. It is the best available blood marker of ovarian reserve β the quantity of eggs remaining. Unlike FSH and estradiol (which fluctuate across the cycle), AMH is relatively stable and can be tested on any cycle day. It declines progressively from the mid-20s and becomes undetectable after menopause.
AMH measures quantity, not quality. A woman with a low AMH can still conceive naturally and through IVF β she simply has fewer eggs and less time. A woman with a normal AMH is not guaranteed good egg quality. Egg quality is primarily determined by age, not AMH. This distinction is critical and consistently misunderstood β by patients and some clinicians.
AMH is complemented by an antral follicle count β a transvaginal ultrasound count of the small resting follicles visible in both ovaries in the early follicular phase. This is the most direct visual assessment of reserve and correlates closely with AMH. Both together give a more complete picture than either alone.
Every woman should know her AMH. It takes one blood test and gives you information that could meaningfully change your decisions about timing, family planning, and whether to consider egg freezing. It is not a test to order when you have already been trying for two years β it is a test to order in your late 20s or early 30s, while options are still open.
Ovarian reserve (quantity) declines in a relatively linear curve from birth β accelerating in the late 30s and 40s. Egg quality follows a different, steeper curve: the proportion of eggs that are chromosomally normal drops sharply after 35 and more steeply after 38. A 25-year-old produces approximately 75% chromosomally normal eggs. By 40, this is closer to 40%. By 43, it may be 15β20%. This is why even women with adequate AMH at 42 face significant IVF challenges.
These are per-cycle figures, not per-attempt cumulative rates. Multiple cycles improve overall chances β but each cycle costs time, money, and emotional capital.
Popular media sometimes frames the cliff as a single sharp drop at 35. In reality it is a gradient β a progressive change that accelerates across the mid to late 30s. There is no biological switch that flips at 35. But there is a meaningful difference in the statistical landscape between 33 and 38 that women deserve to understand before they reach it, not after.
I do not tell women what to do with their fertility timeline β that is not my role. My role is to make sure they have accurate information. The woman who decides at 40 to try for a pregnancy with full knowledge of the statistics has made an informed choice. The woman who reaches 40 believing she had plenty of time because "35 is the new 25" has been failed by the information available to her.
β Dr KD Β· The Longevity ShiftMale factor contributes to approximately 40β50% of all infertility cases. In a further 20β30%, both male and female factors are present. Yet in practice, investigation of the female partner frequently begins before a semen analysis has been performed. A semen analysis is cheap, non-invasive, and should always be the first investigation in any couple presenting with difficulty conceiving.
A semen analysis can look entirely normal while DNA fragmentation β damage to the genetic material inside sperm β is elevated. High DNA fragmentation (>25%) is associated with lower fertilisation rates, poorer embryo development, higher miscarriage rates, and IVF failure despite apparently normal standard parameters. A sperm DNA fragmentation index (DFI) should be tested in men with recurrent miscarriage, repeated IVF failure, or abnormal embryo development even with normal semen analysis.
Male age matters too. Sperm DNA fragmentation increases progressively with age β men over 45 have higher fragmentation rates, and paternal age above 40β45 is associated with increased miscarriage risk and modest increases in certain neurodevelopmental conditions in offspring. Paternal age is not discussed nearly enough in fertility consultations.
PCOS is the most common cause of ovulatory dysfunction, affecting 8β13% of reproductive-age women. The central fertility problem is anovulation β cycles where no egg is released. Without ovulation, conception cannot occur naturally. Irregular cycles (longer than 35 days, or fewer than 8 per year) in a woman with PCOS are a reliable indicator of likely anovulation.
Women with PCOS typically have high antral follicle counts and respond strongly to gonadotrophins. The main risk is ovarian hyperstimulation syndrome (OHSS) β a potentially serious complication involving excessive fluid accumulation. Modern IVF protocols use GnRH agonist triggering and freeze-all strategies to essentially eliminate severe OHSS. This has transformed PCOS IVF safety.
PCOS does not mean infertile. Most women with PCOS who want to conceive will do so β often with relatively simple interventions. The AMH in PCOS is characteristically elevated (reflecting many small follicles), but this does not mean fertility is preserved indefinitely. Egg quality still declines with age. Don't let a high AMH create complacency about timing.
Endometriosis affects approximately 10% of women β and up to 30β50% of those presenting with infertility. The mechanisms are multiple: pelvic inflammation and adhesions can distort tubal anatomy; ovarian endometriomas (chocolate cysts) damage adjacent healthy ovarian tissue and reduce reserve; the inflammatory peritoneal environment may impair sperm function and embryo implantation; and ectopic endometrial tissue appears to affect endometrial receptivity through altered gene expression.
Ovarian endometriomas (cysts of endometriosis within the ovary) are associated with reduced AMH and AFC. Surgery to remove endometriomas further reduces ovarian reserve β sometimes significantly β because the cyst wall is adherent to normal ovarian cortex containing primordial follicles. For a woman planning IVF, the risk-benefit calculation of operating on an endometrioma must weigh pain and IVF access against the cost to reserve.
Laparoscopic excision of stage I/II endometriosis modestly improves natural conception rates (NEJM ENDOAN trial). This is the clearest surgical indication for fertility purposes in early-stage disease.
Complex surgery for stage III/IV or deep infiltrating endometriosis has not been shown to consistently improve IVF outcomes. The decision to operate should be driven by pain and symptom burden β not by the assumption it will improve IVF success.
IVF bypasses many of the peritoneal and tubal factors that impair natural fertility in endometriosis. Live birth rates per cycle in women with endometriosis are generally comparable to other diagnoses when stratified by age and reserve β though women with severe disease and very low AMH face the same reserve-related challenges as any woman with diminished reserve.
A woman with an endometrioma who wants IVF and comes to me for surgery first needs to hear the full picture: that operating may reduce the reserve she needs for that very IVF. Endometriosis surgery before IVF is not automatically right β it is a conversation about her specific anatomy, her pain burden, her reserve, and her timeline. There is rarely one correct answer.
β Dr KD Β· The Longevity ShiftBoth underweight (BMI <18.5) and overweight (BMI >30) are associated with ovulatory dysfunction and reduced fertility. In women with PCOS, weight loss of 5β10% of body weight can restore ovulation without medication. For women undergoing IVF, obesity is associated with lower response, lower fertilisation rates, and lower live birth rates β and many units have BMI thresholds for treatment. Weight is the most modifiable fertility variable.
Even moderate alcohol consumption is associated with reduced fecundity (natural conception rates) in women. The data is dose-dependent but there is no established "safe" level in the preconception period. Both partners should be advised to minimise alcohol intake when trying to conceive β alcohol impairs sperm DNA integrity as well as oocyte quality.
Chronic severe stress (HPA axis activation, elevated cortisol) can suppress the hypothalamic-pituitary-ovarian axis, disrupting ovulation. However, the evidence that everyday fertility-related anxiety directly causes infertility is weak. The damaging narrative that "just relaxing" will fix infertility is unhelpful and puts unwarranted blame on women for their diagnosis. Stress management matters for overall wellbeing during fertility treatment β not as a primary fertility intervention.
Avoid high-dose herbal supplements, adaptogens, and "fertility cleanse" products during fertility treatment. Several (e.g. high-dose Vitex/chasteberry, liquorice root, dong quai) interact with the HPO axis or have estrogenic effects. Always disclose supplements to your fertility specialist before starting a cycle.
Standard advice: try naturally for 12 months under 35, or 6 months over 35, before seeking specialist assessment. This guidance is reasonable for average-risk couples β but it is not a rule that should override clinical red flags. Many women wait the full 12 months before investigation, losing precious time when an identifiable problem existed from the start.
For her: AMH, AFC (transvaginal ultrasound), FSH, LH, estradiol (day 2β3), progesterone (day 21 or 7 days post-ovulation), thyroid function, prolactin, pelvic ultrasound to assess uterine anatomy, and tubal assessment (HSG or HyCoSy) if there is any tubal risk history. For him: full semen analysis. Both partners. First appointment.
The most common reason β at every age β is chromosomal abnormality in the embryo. An abnormal embryo will not implant, or will miscarry. This is not a uterine problem, not a lab problem, and not the woman's fault. It is the primary reason why IVF success rates decline with age: the proportion of chromosomally normal embryos decreases as egg quality declines. PGT-A (genetic testing of embryos) identifies which embryos are chromosomally normal before transfer, improving the per-transfer success rate and reducing miscarriage β though it does not improve the overall number of viable embryos from a cohort.
IVF is not a guarantee. It is a process that maximises the chance of achieving what nature attempts in every cycle β fertilisation and implantation of a viable embryo. The biology still has to work. The most honest conversation a fertility specialist can have is not "IVF will work" but "here is what IVF can do, and here is the realistic chance given your specific situation."
Egg freezing (oocyte cryopreservation) pauses the biological clock for those eggs. A 32-year-old's frozen eggs will have the chromosomal quality of a 32-year-old when used at 38. It does not improve egg quality β it preserves it at the point of freezing. Vitrification (ultra-rapid freezing) has made survival rates on thaw ~90%+, making the process far more reliable than it was a decade ago.
The chance of a live birth from frozen eggs depends critically on how many mature eggs were frozen and at what age. Current data suggests:
The evidence most strongly supports egg freezing between 32 and 36 β old enough to be making a considered decision, young enough that egg quality remains good and fewer cycles are needed. Freezing at 28 is biologically ideal but statistically premature for most women β the majority will conceive naturally. Freezing at 39 is often too late to yield the number and quality of eggs that make the investment worthwhile.
It does not guarantee a baby. It does not eliminate the need for IVF when those eggs are used. It does not address uterine factors, partner fertility, or the logistics of single parenthood if a partner has not been found. It provides an insurance policy β it reduces but does not remove reproductive uncertainty. Women who freeze eggs and then never need them are lucky, not wasteful.
Egg freezing has been marketed as the solution to the biological clock problem. It is not. It is a useful tool with real limitations that requires honest, individualised counselling β not a corporate wellness perk or a reason to delay decisions indefinitely. I want every woman to understand what she is actually buying before she spends the money and goes through the process.
β Dr KD Β· The Longevity ShiftRecurrent miscarriage is defined as two or more pregnancy losses (UK/ESHRE) or three or more (older US definition). It affects approximately 1β2% of couples trying to conceive β far more common than widely appreciated. After three losses, the chance of a fourth is approximately 40% without intervention. Investigations should begin after the second loss β waiting for a third is no longer justified by current guidelines.
Approximately 50β60% of first-trimester miscarriages are caused by chromosomal abnormalities in the embryo β random errors in egg or sperm that are more common with increasing age. These are not caused by anything the woman did. They are not preventable with progesterone, blood thinners, or lifestyle changes. Chorionic villus sampling or products of conception testing after miscarriage can determine if chromosomal abnormality was the cause β this information guides management of subsequent pregnancies.
In approximately 50% of couples investigated for recurrent miscarriage, no cause is found. This is not reassuring β it is a diagnostic gap. "Unexplained" recurrent miscarriage still carries a real recurrence risk, and supportive care (early pregnancy monitoring, progesterone, aspirin in some cases) is still indicated even without a specific diagnosis.
Own-egg IVF after 40 is possible and results in live births. It is not common. The per-cycle live birth rate with own eggs is approximately 15β20% at 40β42, dropping to 5β10% at 43β44, and below 5% after 44. Many women will require multiple cycles. The primary limiting factor is not uterine receptivity (the uterus ages well) β it is egg quality and the declining proportion of chromosomally normal embryos.
Preimplantation genetic testing for aneuploidy (PGT-A) tests embryos for chromosomal normality before transfer. In women over 40, the proportion of euploid (normal) embryos per cohort is low β often 20β40% at 40β42, and lower thereafter. PGT-A improves per-transfer success rates and reduces miscarriage, but cannot improve the total number of euploid embryos available. For women with very low reserve and few embryos per cycle, the decision whether to biopsy (and potentially discard borderline embryos) is nuanced and requires individualised counselling.
Donor egg IVF uses eggs from a younger donor (typically 20β32) fertilised with the partner's or donor sperm, with transfer into the recipient's uterus. Success rates are determined by donor age, not recipient age β making live birth rates 50%+ per transfer for most women regardless of age. The uterus of a 47-year-old, appropriately prepared with estrogen and progesterone, is no less receptive than at 35.
Donor eggs are not "giving up." They are a different path to the same destination. The decision is personal, legal, psychological, and cultural β and it deserves time and proper counselling, not a rushed recommendation at the end of a failed cycle.
Maternal age is the dominant risk factor for chromosomal conditions in the fetus. For women conceiving naturally or through IVF after 40, non-invasive prenatal testing (NIPT) from 10 weeks of pregnancy β a maternal blood test screening for trisomy 21, 18, and 13 β is strongly recommended. Chorionic villus sampling or amniocentesis provides definitive diagnosis where NIPT indicates high risk.
The most important thing I can do for a woman over 40 who wants a baby is to be honest with her β not brutally, not dismissively, but truthfully. She deserves to know what her specific numbers look like, what own-egg IVF can realistically offer, and at what point the conversation about donor eggs becomes the more pragmatic path. False hope costs more than time.
β Dr KD Β· The Longevity Shift"Unexplained infertility" is a diagnosis of exclusion β it means that the standard investigations (semen analysis, ovulation confirmation, tubal patency, uterine anatomy, hormonal profile) have not identified an obvious cause. It accounts for approximately 25β30% of infertility diagnoses. It does not mean "nothing is wrong" β it means the cause has not been identified with the tests performed.
For younger women with unexplained infertility, expectant management or IUI (intrauterine insemination) with ovulation induction is a reasonable first step β cumulative pregnancy rates over 3β6 cycles are comparable to IVF in women under 37 with a shorter duration of infertility. For women over 37, or with infertility duration over 2β3 years, IVF offers a better chance per cycle and should not be unnecessarily delayed.
Unexplained infertility is one of the most frustrating diagnoses to receive β and one of the least satisfying to give. I believe we owe these couples a thorough second layer of investigation before concluding that nothing is findable. The tests we don't do cannot tell us what we are missing.
β Dr KD Β· The Longevity Shift