Recurrent miscarriage — typically defined as three or more pregnancy losses before 24 weeks of gestation — affects approximately 1–2% of couples who are trying to conceive. In clinical practice, many specialist recurrent miscarriage units now begin investigation after two losses, particularly where the losses are consecutive.

Each loss is a bereavement, and the cumulative experience of repeated pregnancy loss has a profound psychological impact. This guide focuses on the clinical picture: what causes recurrent miscarriage, how it is investigated, and where IVF fits in the treatment picture.

Causes of Recurrent Miscarriage

In approximately 50% of cases, no single definitive cause is identified despite thorough investigation. This is an important and often deeply frustrating reality to acknowledge. Of the identified causes:

Chromosomal factors in embryos (most common). The majority of early miscarriages are caused by chromosomal abnormalities in the embryo — too many or too few chromosomes (aneuploidy). This is a random event in most cases, not a structural problem with either parent. The rate of chromosomal abnormality in embryos increases with the egg provider's age, which is why recurrent miscarriage becomes more common with advancing maternal age.

Parental chromosomal abnormalities. In approximately 2–5% of couples with recurrent miscarriage, one parent carries a chromosomal structural rearrangement (typically a balanced translocation or inversion). This is not detectable without specific genetic testing of both parents — it is not visible on standard clinical assessment. Parents with balanced rearrangements are clinically normal but have a higher risk of producing unbalanced embryos that miscarry.

Antiphospholipid syndrome (APS). APS is the most clearly identified and treatable cause of recurrent miscarriage. It is an autoimmune clotting disorder in which antibodies against phospholipids interfere with placentation. It is identified by blood tests (antiphospholipid antibodies, lupus anticoagulant). Where APS is confirmed in the context of recurrent miscarriage, treatment with low-dose aspirin and low-molecular-weight heparin significantly reduces subsequent miscarriage risk.

Uterine structural abnormalities. Congenital uterine anomalies — particularly a uterine septum — are associated with recurrent miscarriage. A septum can be identified on 3D ultrasound or hysteroscopy and treated surgically (hysteroscopic resection). Evidence for the benefit of septal resection on miscarriage rates is variable but surgical correction is generally recommended where a significant septum is found.

Thyroid dysfunction. Both overt and subclinical hypothyroidism are associated with increased miscarriage risk. TSH levels above 2.5 mIU/L in pregnancy are associated with higher miscarriage rates in some studies. NICE guidance recommends testing and treating thyroid dysfunction in recurrent miscarriage patients.

Other factors. Uncontrolled diabetes, severe obesity, thrombophilias (other than APS), and — increasingly in the literature — sperm DNA fragmentation are associated with recurrent miscarriage in some studies.

NHS Investigation for Recurrent Miscarriage

NICE guideline NG126 (2023) sets out the recommended investigation pathway for recurrent miscarriage. NHS investigation is recommended after two losses. The core investigations include:

  • Karyotyping of miscarriage tissue (if products of conception are available): Determines whether the loss was chromosomally abnormal. Where repeated losses show consistently abnormal embryo chromosomes, this suggests a sporadic (random) cause; where embryos are consistently chromosomally normal, maternal or uterine factors are more likely.
  • Parental karyotype (blood test for both partners): Identifies balanced chromosomal rearrangements.
  • Antiphospholipid antibody testing (two tests at least 12 weeks apart to confirm positive findings).
  • Thyroid function (TSH).
  • Pelvic ultrasound (3D if possible) to assess uterine anatomy.
  • HbA1c (if diabetes is suspected or at higher risk).

NHS recurrent miscarriage clinics (usually based in larger hospitals) typically see patients after two or three losses and coordinate this investigation.

The Role of IVF in Recurrent Miscarriage

IVF with preimplantation genetic testing for aneuploidy (PGT-A) is increasingly used in recurrent miscarriage management, with the goal of identifying chromosomally normal embryos before transfer. The logic is straightforward: if most miscarriages are due to aneuploid embryos, testing embryos before transfer and only transferring euploid ones should reduce miscarriage rates.

The evidence for this is complex:

  • PGT-A does substantially reduce the miscarriage rate per transfer in patients with recurrent pregnancy loss
  • However, whether it improves cumulative live birth rates (compared to continuing to try without testing) is debated — some evidence suggests the overall outcome across multiple attempts with and without PGT-A is similar
  • For patients with parental balanced translocations, PGT-SR (structural rearrangement testing, a form of PGT tailored to the specific translocation) is more clearly beneficial than PGT-A

PGT-A is most likely to be genuinely beneficial in recurrent miscarriage where:

  • Maternal age is above 37 (higher baseline aneuploidy rate)
  • Multiple previous losses have been confirmed as chromosomally normal (pointing away from random aneuploidy as the cause)
  • There are sufficient embryos per cycle to make testing worthwhile

For full detail on PGT types and evidence, see preimplantation genetic testing.

Treatments That Do Not Have Established Evidence

A number of treatments are widely promoted for recurrent miscarriage without sufficient trial evidence to support routine use:

Progesterone supplementation in early pregnancy: The PRISM trial (2019) showed a benefit of vaginal progesterone for women with a history of one or more previous miscarriages who presented with early pregnancy bleeding. NICE now recommends progesterone for this indication. However, for women with recurrent miscarriage who have not yet had a positive test in the current pregnancy, the evidence is less clear. Many UK clinics do prescribe early progesterone supplementation in recurrent miscarriage patients as a precautionary measure.

Immunoglobulin infusions / intralipids: Proposed for patients with immune-based recurrent miscarriage. Evidence from trials is insufficient to recommend these outside research settings.

NK cell testing and immunosuppression: As discussed in recurrent implantation failure, the evidence base for NK cell testing and immune-modulating treatments in recurrent miscarriage is not established. The HFEA does not recommend these routinely.

Psychological Support

Recurrent pregnancy loss requires psychological support that is often inadequately provided within standard NHS pathways. Specialist recurrent miscarriage units typically have an associated counsellor or psychologist; if your care is provided at a general gynaecology clinic, you may need to ask specifically for a referral.

The Miscarriage Association provides peer support, resources, and a helpline specifically for pregnancy loss in the UK. The IVF and fertility mental health support described in IVF and mental health support is also relevant.

Frequently Asked Questions

Q: Does having three miscarriages mean I can never have a baby?

A: No. Even after three miscarriages without treatment, the chance of a successful subsequent pregnancy is approximately 65–70%. With investigation and treatment of identified causes, this improves further. Recurrent miscarriage is a serious and distressing condition, but many people with this diagnosis do go on to have successful pregnancies.

Q: Should I have IVF after recurrent miscarriage even if I conceive naturally?

A: IVF with PGT-A is sometimes offered to couples who can conceive naturally but have experienced recurrent loss due to chromosomal abnormalities. The rationale is to test embryos before transfer rather than experiencing further losses. Whether this is the right approach depends on age, embryo numbers per cycle, and the specific cause of the losses — discuss with a specialist recurrent miscarriage consultant.

Q: Will taking aspirin or heparin help?

A: Aspirin and heparin (specifically low-molecular-weight heparin, LMWH) are the established treatment for recurrent miscarriage due to antiphospholipid syndrome (APS). If you have confirmed APS, this treatment substantially reduces subsequent miscarriage risk. If you do not have APS, there is no good evidence that aspirin and heparin improve outcomes — though some clinics prescribe them empirically in unexplained recurrent miscarriage. Discuss with your specialist whether this is appropriate for your situation.

Q: How long should I wait after a miscarriage before trying again?

A: NICE guidance does not recommend a minimum waiting period between miscarriage and trying to conceive again, and evidence from a large study suggests that pregnancy after miscarriage is not associated with worse outcomes than after waiting. Emotionally, many people need time. Physically, it is generally safe to try again after one full menstrual cycle — which allows accurate dating of a subsequent pregnancy.

Q: My miscarriage tissue was tested and was chromosomally normal. What does that mean?

A: A chromosomally normal miscarriage suggests the embryo had the right number of chromosomes and the loss was due to another cause — possibly maternal or uterine factors. This is an important finding that shifts the investigation focus away from embryo chromosomal issues and toward antiphospholipid syndrome, uterine anatomy, or other maternal factors.

This article is for information only and does not constitute medical advice. Recurrent miscarriage investigation and treatment should be managed by a specialist.