Recurrent pregnancy loss investigation

01Purpose and principlesWhat the assessment is for and the core concepts behind it.

Recurrent loss is a pattern, not a single diagnosis. Embryonic chromosomal error remains common and becomes more likely with increasing maternal age, yet persistent maternal, paternal or pregnancy factors can also contribute. Recognised associations include antiphospholipid syndrome, congenital uterine anomalies, parental balanced chromosome rearrangement, thyroid dysfunction or antibodies, poorly controlled diabetes, extremes of weight, smoking and excess alcohol or caffeine. Even after careful assessment, many cases remain unexplained.

The investigation should answer a practical question: will this result change preconception care, treatment or surveillance in the next pregnancy? Broad immune, infection and thrombophilia panels produce incidental abnormalities without proven benefit. A clinic that combines evidence-based testing, clear interpretation, genetics or medical referral where indicated and supportive early ultrasound is more valuable than indiscriminate testing.

Use inclusive and trauma-informed consultations. Ask how the person describes each pregnancy, whom they want involved, and what has already been investigated. Do not imply that exercise, ordinary work, sex or emotional stress caused the losses. Discuss age and modifiable associations accurately but without assigning responsibility for a usually multifactorial event.

Key points

RCOG defines recurrent miscarriage as three or more first-trimester miscarriages; they need not be consecutive or with the same partner.
Use clinical discretion to investigate after two first-trimester losses when their pattern suggests pathology rather than independent sporadic events.
Start with a verified pregnancy timeline, maternal and paternal age, gestations, ultrasound or histology findings, complications, conditions, medicines, family history and lifestyle.
Core tests include antiphospholipid antibodies, thyroid function with thyroid peroxidase antibodies, and pelvic ultrasound to assess uterine anatomy.
Confirm antiphospholipid syndrome with persistent qualifying antibodies on two samples at least 12 weeks apart and at least 6 weeks after miscarriage.
Offer cytogenetic testing of pregnancy tissue from the third and subsequent miscarriage; parental karyotyping is selected by tissue results or inability to obtain an informative result.
Do not routinely order inherited thrombophilia panels, natural-killer-cell assays, HLA or cytokine tests, infection screens or sperm DNA fragmentation for recurrent first-trimester loss.
Confirmed obstetric APS is treated in pregnancy with low-dose aspirin plus heparin; do not give either empirically for unexplained recurrent miscarriage.
Progesterone is not routine prophylaxis while asymptomatic, but NICE offers vaginal micronised progesterone 400 mg twice daily for scan-confirmed intrauterine pregnancy with bleeding and any previous miscarriage.

02Indications, selection and cautionsWhen it is useful, when urgency changes and important limitations.

RCOG definition

Three or more first-trimester miscarriages meet the definition whether consecutive or not and whether occurring with one or different partners.

Earlier evaluation

After two first-trimester losses, consider a full work-up when gestation, morphology, family history, thrombosis, uterine history or another feature suggests a non-sporadic mechanism.

Second-trimester pattern

One or more second-trimester miscarriages require attention to fetal genetics, APS, uterine anatomy, infection or placental disease, and a history suggesting cervical insufficiency.

Verified chronology

Separate biochemical loss, confirmed intrauterine miscarriage, ectopic and molar pregnancy; record gestation, fetal heartbeat, scan, pathology, management and any placental or fetal findings for every event.

Emotional burden

Repeated loss may produce grief, hypervigilance, depression, anxiety or post-traumatic symptoms even when the person appears composed; ask directly and offer support rather than assuming resilience.

Red flags requiring action

Current severe pain, syncope, shoulder-tip pain, peritonism or haemodynamic compromise requiring emergency ectopic assessment.
Current heavy bleeding, fever, offensive discharge or systemic illness suggesting haemorrhage or infected miscarriage.
Previous second-trimester painless cervical dilatation, membrane rupture or very preterm birth suggesting cervical insufficiency and future specialist planning.
Personal thrombosis, systemic lupus features or previous severe placenta-mediated disease raising concern for antiphospholipid syndrome.
Severe depression, trauma symptoms, inability to function, self-harm thoughts or immediate safeguarding concerns after repeated losses.

03Method and interpretationA systematic approach to the test and its findings.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Antiphospholipid antibody panelFirst step
Why
Detect an acquired, treatable thrombophilia associated with recurrent and later pregnancy loss.
Interpretation and limitations
Test lupus anticoagulant and anticardiolipin antibodies, with anti-beta-2-glycoprotein I according to the APS pathway. Diagnosis requires qualifying persistence on two tests at least 12 weeks apart and sampling at least 6 weeks after miscarriage; one low positive is not APS.
02
Thyroid function and TPO antibodies
Why
Identify overt or subclinical thyroid dysfunction and thyroid autoimmunity that alter counselling or surveillance.
Interpretation and limitations
Interpret TSH against the laboratory and pregnancy context with free T4 when indicated. Treat overt disease; an isolated antibody result in an euthyroid person does not automatically justify levothyroxine, but warrants preconception or early-pregnancy thyroid review.
03
Pelvic ultrasound with uterine assessment
Why
Look for congenital uterine anomalies, intracavity fibroids, polyps or adhesions.
Interpretation and limitations
Three-dimensional transvaginal ultrasound is preferred when available for uterine morphology. Abnormal or uncertain anatomy may require specialist ultrasound, saline infusion imaging, hysteroscopy or MRI; the presence of a lesion does not prove that surgery improves live birth.
04
Pregnancy-tissue cytogenetics
Why
Determine whether a third or later miscarriage resulted from a chromosomal abnormality and guide parental testing.
Interpretation and limitations
Use an appropriate tissue test through genetics and pathology, mindful of maternal-cell contamination and test failure. An unbalanced result may point to a parental rearrangement; a sporadic aneuploid result can explain that loss without predicting every future pregnancy.
05
Parental karyotypes
Why
Find a balanced rearrangement when pregnancy tissue suggests inheritance or no informative tissue result is available.
Interpretation and limitations
Do not treat karyotyping as an automatic first test for every couple. An abnormal result needs clinical-genetics counselling about natural conception, prenatal diagnosis and assisted-reproduction options, including uncertain comparative live-birth benefit.
06
Targeted metabolic and endocrine tests
Why
Investigate diabetes, prolactin imbalance or PCOS when history or examination makes them plausible.
Interpretation and limitations
Use HbA1c for relevant diabetes risk and prolactin only with symptoms such as galactorrhoea or cycle disturbance. Routine ovarian-reserve or broad hormone panels do not explain most recurrent losses.
07
Tests usually not indicated
Why
Prevent low-value investigations from being mistaken for validated causes.
Interpretation and limitations
Routine first-trimester inherited thrombophilia screens, natural-killer-cell number or activity, HLA compatibility, cytokines, infection panels and sperm DNA fragmentation lack evidence for improving outcomes and should not drive unproven treatment.

04Clinical next stepsHow the result changes management or prompts escalation.

01Referral and baseline work-upVerify the phenotype before testingFirst stepThere are three first-trimester miscarriages, an eligible later loss, or two early losses with features suggesting pathology.

1Reconstruct every pregnancy with records where available and take medical, obstetric, thrombotic, genetic, medication, family, social and reproductive histories.
2Offer APS testing, thyroid function with TPO antibodies and uterine ultrasound, then arrange pregnancy-tissue or parental genetic testing according to the loss number and available specimen.
3Screen emotional wellbeing and safety, discuss modifiable associations without blame, and agree how results and future-pregnancy access will be communicated.

02Abnormal resultLink each finding to specialist actionTesting identifies persistent APS antibodies, thyroid disease, a uterine anomaly, abnormal tissue genetics or another credible condition.

1Confirm that diagnostic criteria are met rather than acting on a single borderline result, and explain absolute uncertainty in plain language.
2Refer to the relevant recurrent-loss, haematology, endocrine, fetal-medicine, reproductive-medicine or clinical-genetics service for a shared plan.
3Document preconception treatment, medicine timing, antenatal surveillance and emergency contacts before the next pregnancy where possible.

03Unexplained recurrent lossAvoid empirical anticoagulationEvidence-based investigation is complete and no actionable cause has been established.

1Explain that unexplained does not mean imaginary or caused by the patient, and give an individual prognosis influenced chiefly by age and pregnancy history.
2Do not prescribe aspirin, heparin, steroids, intravenous immunoglobulin or immune therapies solely because losses are unexplained.
3Offer an experienced supportive-care team, a route for early contact and reassurance ultrasound in the next pregnancy, plus psychological support if wanted.

04Next pregnancyActivate the agreed plan earlyA new pregnancy test is positive after recurrent miscarriage.

1Arrange prompt contact with the designated service and start only indication-based pre-agreed treatment, such as APS anticoagulation or thyroid replacement.
2Provide early ultrasound at an informative interval, assessing pain or bleeding urgently rather than using serial testing only for reassurance.
3If scan-confirmed intrauterine pregnancy is accompanied by bleeding and there has been any previous miscarriage, offer vaginal micronised progesterone 400 mg twice daily and continue to 16 completed weeks if heartbeat is confirmed.

05Procedure and medicine safetyRelevant preparation, treatment and contraindications.

The combination improves successful pregnancy rates in recurrent miscarriage associated with confirmed antiphospholipid syndrome and also addresses pregnancy-related thrombotic risk.

Low-dose aspirin plus heparin for confirmed obstetric APS

Use a specialist pregnancy plan: low-dose aspirin 75 to 150 mg orally once daily plus prophylactic unfractionated heparin or weight-adjusted low-molecular-weight heparin by subcutaneous injection; exact start, product, dose and stop timing depend on APS, thrombosis history, weight and delivery plan.

Do not use for a single transient antibody result or unexplained recurrent miscarriage; assess bleeding, ulcer, aspirin sensitivity, renal function, platelet count, previous heparin-induced thrombocytopenia, neuraxial timing and peripartum interruption with obstetric and haematology teams.

Reduces miscarriage in the defined bleeding-plus-previous-loss group; recurrent miscarriage alone without bleeding is not an evidence-based indication for routine prophylaxis.

Vaginal micronised progesterone

Offer 400 mg vaginally twice daily when ultrasound confirms an intrauterine pregnancy and early-pregnancy bleeding occurs after at least one previous miscarriage; if a fetal heartbeat is confirmed, continue until 16 completed weeks.

Do not use progesterone to bypass assessment of pregnancy location, viability, ectopic symptoms or haemodynamic danger; explain local irritation, discharge, headache and the defined stopping point.

Restores euthyroidism where overt thyroid dysfunction is present, reducing avoidable maternal and pregnancy complications.

Levothyroxine for established hypothyroidism

Continue or initiate an individually titrated oral daily dose based on TSH and free T4, with early pregnancy testing and dose adjustment by the endocrine or obstetric plan rather than a fixed recurrent-loss regimen.

Do not automatically treat an euthyroid person solely for TPO-antibody positivity; separate tablets from iron or calcium, avoid overtreatment and repeat thyroid function promptly after conception and dose changes.

06Risks, monitoring and follow-upComplications, safety checks and further assessment.

Track every ordered result to interpretation and communicate it in the agreed format; repeated loss makes unexplained delays especially harmful.
Repeat a positive APS panel at least 12 weeks later and ensure testing is at least 6 weeks after miscarriage before labelling persistent APS.
For thyroid disease, optimise before conception and recheck early in pregnancy and after any levothyroxine adjustment using condition-specific targets.
If aspirin and heparin are prescribed, monitor bleeding, platelet and renal considerations and coordinate interruption around procedures, miscarriage or delivery.
Record the next-pregnancy route, early scan timing, cervical or fetal-medicine surveillance and who the patient can contact without a new referral.
At each visit review grief, anxiety, trauma, sleep, work and relationship impact, offering formal mental-health or bereavement support according to preference and risk.

07Special situationsVariants, exceptions and circumstances that change the usual approach.

Losses need not be consecutive

Healthy pregnancies between miscarriages and different partners do not remove the RCOG definition because maternal mechanisms can persist.

Two can justify discretion

A suspicious clinical pattern after two losses may warrant the same evaluation rather than forcing a third event before investigation.

APS requires persistence

One antibody result is insufficient; the time-separated repeat prevents transient positivity from becoming a lifelong diagnosis and treatment burden.

Test tissue before parents

Pregnancy-tissue cytogenetics often identifies a sporadic cause and helps target parental karyotyping and genetic counselling.

Support is active care

A named team, prompt access and reassurance scans improve experience even when no medicine has been shown to prevent unexplained loss.

08Common pitfallsFrequent interpretation and management errors.

01
Refusing evaluation until three losses despite two events with a strongly pathological pattern.
02
Counting ectopic or molar pregnancy as though it were a confirmed intrauterine miscarriage without reconstructing the history.
03
Diagnosing APS from one low-positive sample or repeating the panel too soon after loss.
04
Ordering inherited thrombophilia, immune or infection panels routinely and then treating incidental results.
05
Giving aspirin or heparin empirically for unexplained recurrent miscarriage.
06
Offering progesterone throughout every pregnancy without the evidence-based combination of prior miscarriage and current bleeding.
07
Presenting weight, smoking or age associations in a blaming way or promising that modifying them guarantees a live birth.
08
Stopping after normal tests without a documented supportive-care plan for the next pregnancy.