Recurrent Miscarriage: What Actually Needs Investigating

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After a second miscarriage, most women aren't looking for reassurance that "it just happens." They're looking for a plan — what tests to ask for, what might be missed, and whether anything about their body, their blood work, or their diet could be quietly working against them. That instinct is the right one. Recurrent miscarriage isn't something to wait out indefinitely; it's something to investigate systematically, alongside a fertility specialist, while also looking honestly at the modifiable factors — nutrition, metabolic health, and lifestyle — sitting underneath the hormonal and immune picture.

Quick answer: what actually needs investigating after recurrent miscarriage?

A recurrent miscarriage workup typically evaluates genetic factors (chromosomal analysis of pregnancy tissue and, in some cases, parental karyotyping), uterine anatomy, endocrine factors (thyroid function, prolactin, ovarian reserve), and antiphospholipid antibody testing. Around half of cases remain unexplained even after full evaluation. Nutrition doesn't replace this workup, but insulin resistance, vitamin D status, and thyroid antibody levels — all nutrition-relevant — are increasingly recognised as part of the picture worth reviewing.

What Counts as "Recurrent" Miscarriage?

Definitions vary slightly by guideline. ASRM defines recurrent pregnancy loss (RPL) as two or more failed clinical pregnancies, while some European guidelines still reference three. In practice, most reproductive endocrinologists — and the newest 2026 ASRM committee opinion — now support starting the evaluation after the second loss rather than waiting for a third, particularly for women over 35 or when a loss has occurred quickly after the previous one. If you've had two consecutive losses, it's reasonable to ask your doctor for genetic testing of the pregnancy tissue and a baseline evaluation rather than being told to "just try again."

Miscarriage itself is common — around 1 in 5 confirmed pregnancies end this way, most from chromosomal causes unrelated to anything the mother did. Recurrent loss is different: it's a pattern that deserves a structured investigation rather than repeated reassurance.

The Standard Medical Investigation, Explained

Genetic evaluation. Chromosomal abnormalities are the single most common identifiable cause of both sporadic and recurrent miscarriage, and their likelihood rises with maternal age. Current ASRM guidance now recommends offering genetic testing of the miscarriage tissue after the second loss — this can meaningfully narrow down whether a loss was a one-off chromosomal event or points toward something else.

Uterine anatomy. Structural issues — a septate uterus, fibroids distorting the cavity, or scar tissue from a prior procedure — can be assessed with pelvic ultrasound, saline sonogram, or hysteroscopy.

Endocrine factors. Thyroid function (TSH, and often thyroid antibodies), prolactin, and sometimes ovarian reserve markers are standard. Both overt and subclinical thyroid dysfunction, and thyroid autoimmunity even in women with "normal" TSH, have been associated with higher miscarriage rates in multiple studies.

Antiphospholipid syndrome (APS) and thrombophilia. APS is found in roughly 15–20% of women with RPL and is one of the few causes with a clearly established treatment pathway (typically aspirin and/or heparin under medical supervision). Inherited thrombophilias are tested more selectively, since the evidence linking them causally to pregnancy loss is weaker than once assumed.

What's often left out — but shouldn't be. Fasting insulin, HbA1c or an oral glucose tolerance test, and vitamin D levels are not yet universal in every clinic's RPL panel, despite a growing body of evidence connecting them to pregnancy loss risk. If your workup hasn't included these, it's worth asking about.

Even with a complete evaluation, more than half of RPL cases are classified as "unexplained." That's not the same as "nothing is wrong" — it often means the cause sits in an area evaluation can't yet fully capture, including the metabolic and nutritional factors below.

Where Metabolic and Nutritional Factors Fit Into the Picture

This is the part of the investigation that's easiest to overlook, and it's where nutrition genuinely has something meaningful to contribute.

Insulin resistance. A 2022 systematic review and meta-analysis pooling data from over 4,000 women found that those with recurrent pregnancy loss had significantly higher fasting insulin, higher fasting glucose, and greater insulin resistance (measured by HOMA-IR) than women with a normal pregnancy history. The proposed mechanism involves insulin resistance disrupting endometrial receptivity and creating an abnormal metabolic environment during early implantation. This is separate from, but often overlaps with, PCOS — insulin resistance can be present with or without a formal PCOS diagnosis.

Vitamin D status. A 2025 meta-analysis found maternal vitamin D deficiency was consistently associated with higher miscarriage risk, plausibly through its role in immune regulation at the placental interface. Deficiency has also been linked to a higher likelihood of autoimmune markers — including thyroid and antiphospholipid antibodies — in women with RPL, suggesting these factors may not act in isolation.

Thyroid autoimmunity. Thyroid antibody positivity is more common in women with RPL than in the general population, and has been linked to lower live birth rates even when TSH itself looks normal. Nutrition can support thyroid-relevant nutrient status (iodine, selenium, iron, zinc) but cannot resolve autoimmune thyroid disease on its own — that needs endocrinology input.

At a glance — nutrition-relevant factors worth reviewing

Factor	Why it's relevant	Typical test
Insulin resistance	Associated with higher RPL risk in meta-analysis data	Fasting insulin, HbA1c, OGTT
Vitamin D	Deficiency linked to higher miscarriage risk and autoimmune markers	Serum 25(OH)D
Thyroid antibodies	Linked to lower live birth rates even with normal TSH	TPO antibodies, TSH
Iron, B12, folate	Deficiencies affect homocysteine and cellular metabolism relevant to implantation	Iron studies, B12, folate

Practical takeaway: if your RPL evaluation hasn't included fasting insulin, HbA1c and vitamin D, these are reasonable, low-cost additions to raise with your doctor alongside the standard genetic, anatomical and antibody workup.

What Diet and Lifestyle Changes Are Actually Linked to Lower Risk

None of this is about a single "miscarriage-proof" food. It's about the overall pattern.

A heart-healthy dietary pattern. Emerging research comparing dietary patterns in women with RPL found that closer adherence to an AHA-style diet — rich in vegetables, fruit, whole grains, lean protein and unsaturated fats, lower in refined carbohydrate and processed food — during the preconception period was associated with a lower risk of pregnancy loss and other adverse outcomes. This mirrors patterns long recommended for insulin sensitivity and cardiometabolic health more broadly.
Blood sugar regulation. Given the insulin-resistance link above, meal patterns that reduce large glucose swings — adequate protein and fibre at each meal, limiting refined carbohydrate loads, regular meal timing — are a reasonable, evidence-aligned focus, particularly for women with PCOS, higher BMI, or a family history of diabetes.
Correcting specific deficiencies. Where blood work shows low vitamin D, iron, B12 or folate, correcting these through diet and, where needed, supplementation under guidance is a modifiable step with plausible relevance to implantation and placental health.
Body composition and activity. Both very low and very high BMI are associated with higher pregnancy loss risk in observational data; movement and gradual, sustainable weight management (where relevant) support the same metabolic pathways as diet.
Alcohol, smoking and caffeine. These remain independently associated with pregnancy loss risk in cohort data and are worth addressing regardless of what else the investigation finds.

Consider a couple where the female partner has had two losses, mildly elevated fasting insulin, and a vitamin D level in the "insufficient" range, alongside a completely normal genetic and anatomical workup. Her nutrition plan in this case isn't a generic "fertility diet" — it's built around correcting the vitamin D deficiency, restructuring meals to reduce glucose spikes, and monitoring how her cycle and blood work respond over 2–3 months, in parallel with her fertility specialist's ongoing evaluation.

What Nutrition Cannot Do

This needs to be said plainly. Nutrition cannot correct a chromosomal abnormality, resolve a uterine septum, treat antiphospholipid syndrome, or reverse unexplained RPL. It cannot guarantee a future pregnancy will succeed. Where a cause is identified — genetic, anatomical, or autoimmune — medical or surgical treatment is the primary pathway, with nutrition playing a supportive, not corrective, role. Anyone who has had two or more losses should be under the care of a gynaecologist or fertility specialist for the core investigation; nutrition support works alongside that care, not instead of it.

FAQs

How many miscarriages count as "recurrent"?

Most current guidelines, including the 2026 ASRM committee opinion, support starting a full evaluation after two consecutive losses rather than waiting for three, especially for women over 35. Some earlier guidelines used three losses as the threshold, so terminology can still vary between clinics.

Can diet alone prevent another miscarriage?

No single diet can guarantee a successful pregnancy. Nutrition may help address modifiable factors — insulin resistance, vitamin D deficiency, and general metabolic health — that are statistically associated with higher miscarriage risk, but it works alongside, not instead of, a proper medical investigation.

Is insulin resistance tested as part of a standard RPL workup?

Not always, even though a 2022 meta-analysis of over 4,000 women found a clear association between insulin resistance and recurrent pregnancy loss. It's reasonable to specifically ask your doctor for fasting insulin, HbA1c or an OGTT if this hasn't been included.

Does vitamin D deficiency actually cause miscarriage?

Current evidence shows a consistent association between low vitamin D and higher miscarriage risk, plausibly through immune regulation at the placenta, but this is not the same as proven causation. Correcting a genuine deficiency is a low-risk, reasonable step regardless.

What if all my tests come back normal?

Unexplained RPL is common — over half of cases remain unexplained even after complete evaluation. This isn't the same as nothing being wrong; it often reflects factors current testing can't fully capture, which is one reason metabolic and nutritional review is increasingly recommended even when standard tests are clear.

Should I see a fertility specialist or my regular gynaecologist first?

After a second loss, a referral to a reproductive endocrinologist or fertility specialist is reasonable, particularly if you're over 35 or the losses have been close together. They can order the fuller genetic, anatomical and antibody panel that a general practice visit may not include.

Can PCOS or thyroid issues cause recurrent miscarriage?

Both are associated with higher miscarriage risk — PCOS largely through insulin resistance, and thyroid dysfunction (including antibody positivity with normal TSH) through its effect on early pregnancy hormonal support. Both are assessable and, to varying degrees, manageable with the right medical and nutritional support.

Where Personalised Support Fits In

A generic "fertility diet" can't account for your specific blood work, your miscarriage history, your BMI, or whether insulin resistance, thyroid antibodies or a nutrient deficiency are actually part of your picture. That's the gap individualised nutrition support is meant to close.

At Health Hatch, our Registered Dietitians work alongside your fertility specialist's investigation rather than in place of it. The process typically starts with a personalised fertility assessment — a review of your hormonal profile, blood work (including fasting insulin, vitamin D and thyroid markers where relevant), cycle history and current diet — so that any nutrition plan is built around what's actually showing up in your results, not a one-size-fits-all list of "fertility foods." If you're navigating recurrent miscarriage and want your nutrition and metabolic health properly reviewed alongside your medical workup, you can enquire about a personalised fertility assessment with our team.

References

American Society for Reproductive Medicine. Recurrent pregnancy loss: a committee opinion (2026).
ESHRE Guideline Group on RPL. ESHRE guideline: recurrent pregnancy loss — an update in 2022. Human Reproduction Open, 2023.
Insulin resistance in women with recurrent miscarriage: a systematic review and meta-analysis. BMC Pregnancy and Childbirth, 2022.
Shedding light on gestational loss: the role of Vitamin D 25(OH)D deficiency in miscarriage — a systematic review and meta-analysis. 2025.
Dietary patterns and recurrent pregnancy loss: a comparison of the American Heart Association diet, Mediterranean diet and others. Frontiers in Nutrition.
Thyroid autoimmunity and obstetric outcomes in women with recurrent miscarriage: a case–control study. Endocrine Connections, 2013.

recurrent miscarriagepregnancy lossfertilitypreconceptiontrying to conceiveinsulin resistance