What are the latest ESHRE and ASRM recommendations for recurrent pregnancy loss evaluation and management?

[Terminology: PCOS was renamed polyendocrine metabolic ovarian syndrome (PMOS) by global consensus in May 2026, published in The Lancet. The International Guideline now uses PMOS/PCOS in its recommendations and will use PMOS alone from 2028. Clinical content, diagnostic criteria and management are unchanged.]

Definition. ASRM (2026) defines RPL as the spontaneous loss of two or more pregnancies, excluding confirmed molar and ectopic pregnancies. Three points are easily missed: pregnancies confirmed by urinary or blood hCG are sufficient — ultrasound or tissue confirmation is not required; biochemical losses count, as they confer similar recurrence risk to clinical losses; and losses need not be consecutive. Losses are defined as under 22 weeks. Evaluation follows a stepwise algorithm built on chromosome testing of the miscarriage. First step — chromosome analysis of miscarriage tissue, offered to all patients at their second miscarriage or with a history of RPL. Array-based technology is recommended over conventional karyotyping, which has 10–40% culture failure, maternal cell contamination, and cannot detect microdeletions under 5 Mb. At-home collection kits should be discussed for patients not having surgical management. An aneuploid result explains the loss and avoids an expensive workup. Recommended for all — uterine cavity evaluation by HSG, saline sonogram or hysteroscopy. Recommended in specific circumstances: Parental karyotypes — where miscarriage testing shows an unbalanced translocation, or where no miscarriage testing was done. Antiphospholipid antibodies — where clinical criteria for APS are met. If all miscarriages are aneuploid, aPL testing is not recommended. TSH — with risk factors or symptoms, euploid miscarriage, or no miscarriage testing. HbA1c — where diabetes risk factors are present (raised BMI, family history, age over 40, PCOS, prior gestational diabetes). Sperm DNA fragmentation — unexplained RPL or concurrent infertility. Prolactin — only with symptoms such as galactorrhoea or anovulation. Not recommended: inherited thrombophilia screening, thyroid antibodies, NK cell testing, endometrial receptivity testing, microbiome testing including mycoplasma and ureaplasma, routine ovarian reserve testing. Counselling point: 50–80% of patients with unexplained RPL succeed in a subsequent pregnancy with no specific intervention. ASRM frames conveying this as a provider responsibility.