Residency · Residency · Obstetrics Gynecology
Recurrent Pregnancy Loss
Definitions
Recurrent pregnancy loss is defined by ASRM as two or more clinically recognized pregnancy losses. The more traditional ACOG definition uses three or more consecutive losses as the threshold. Clinical pregnancy loss refers to a pregnancy documented by ultrasound or histopathology, not biochemical-only pregnancies. Sporadic miscarriage occurs in 10 to 15% of clinically recognized pregnancies. Recurrent pregnancy loss affects 1 to 2% of couples. After two losses, the risk of another miscarriage is 25 to 30%, and after three losses, it rises to 30 to 40%.
Etiology
Chromosomal/Genetic (50-60% of Sporadic Losses)
Embryonic aneuploidy is the most common cause of sporadic first-trimester pregnancy loss. The most frequent abnormalities are trisomies, followed by monosomy X, triploidy, and tetraploidy. The incidence of aneuploidy increases with maternal age. Parental balanced structural chromosomal rearrangements are found in 3 to 5% of couples with recurrent pregnancy loss. These include balanced reciprocal translocations, Robertsonian translocations, and inversions. The carrier parent is phenotypically normal but produces unbalanced gametes that lead to nonviable pregnancies. Karyotyping of both partners is recommended. Products of conception testing using chromosome analysis or chromosomal microarray on miscarriage tissue helps determine whether a given loss was chromosomal in origin.
Uterine Anatomic Factors (10-15%)
The uterine septum is the most common Mullerian anomaly associated with recurrent pregnancy loss, carrying a miscarriage risk of approximately 60%. Hysteroscopic septum resection improves outcomes. Submucosal fibroids impair implantation and placentation. Endometrial polyps may interfere with implantation. Asherman syndrome (intrauterine adhesions) impairs endometrial receptivity. Bicornuate, unicornuate, and didelphys uteri are more commonly associated with second-trimester loss and preterm birth than with first-trimester recurrent loss. Cervical insufficiency similarly causes second-trimester rather than first-trimester losses.
Antiphospholipid Syndrome (5-15%)
Antiphospholipid syndrome is the most important treatable cause of recurrent pregnancy loss. It is an autoimmune condition with both thrombotic and obstetric manifestations. The revised Sapporo/Sydney diagnostic criteria require at least one clinical criterion and at least one laboratory criterion. The obstetric clinical criteria include one or more unexplained deaths of a morphologically normal fetus at 10 weeks or beyond, one or more premature births before 34 weeks due to preeclampsia, eclampsia, or placental insufficiency, or three or more consecutive unexplained losses before 10 weeks. The laboratory criteria, which must be positive on two occasions at least 12 weeks apart, include lupus anticoagulant, anticardiolipin antibodies (IgG or IgM) at medium or high titer, and anti-beta-2-glycoprotein I antibodies (IgG or IgM).
| Criteria Type | Requirement |
|---|---|
| Clinical (≥1 required) | |
| Fetal death | ≥1 unexplained death of morphologically normal fetus at ≥10 weeks |
| Preterm birth | ≥1 premature birth <34 weeks due to preeclampsia/eclampsia/placental insufficiency |
| Early losses | ≥3 consecutive unexplained losses <10 weeks |
| Laboratory (≥1 required, positive on 2 occasions ≥12 weeks apart) | |
| Lupus anticoagulant | Positive |
| Anticardiolipin antibodies | IgG or IgM, medium or high titer |
| Anti-beta-2-glycoprotein I | IgG or IgM |
Endocrine Factors
Overt hypothyroidism has a well-established association with recurrent pregnancy loss. Subclinical hypothyroidism with a TSH above 2.5 to 4.0 is controversial, but treatment with levothyroxine is low-risk. Thyroid peroxidase antibodies are associated with recurrent loss independent of TSH level. Uncontrolled diabetes mellitus with elevated hemoglobin A1C at conception increases miscarriage risk. Hyperprolactinemia may impair corpus luteum function. Luteal phase deficiency has historically been blamed for recurrent loss but is now considered poorly defined and of uncertain clinical significance. PCOS is associated with increased miscarriage risk through mechanisms related to insulin resistance, hyperandrogenism, and elevated LH.
Thrombophilia
Inherited thrombophilias including factor V Leiden (with a heterozygous odds ratio of 1.5 to 2 for recurrent loss), prothrombin gene mutation (G20210A), and deficiencies of protein C, protein S, and antithrombin have been studied in recurrent loss. The association is modest and controversial. ACOG and ASRM do not recommend routine thrombophilia testing for recurrent pregnancy loss unless there is a personal or family history of venous thromboembolism. Treatment with heparin and aspirin for inherited thrombophilia in recurrent loss lacks strong randomized controlled trial support, with antiphospholipid syndrome being the notable exception.
Immunologic Factors
Natural killer cell testing and immunotherapy are not recommended by ACOG or ASRM, as no evidence supports their use. Peripheral blood NK cell levels do not predict pregnancy outcome. Intralipid infusions, intravenous immunoglobulin, and corticosteroids for "immune" recurrent loss lack supporting evidence.
Male Factor
Sperm DNA fragmentation is an area of emerging research, with evidence linking high fragmentation to recurrent pregnancy loss. Paternal age and sperm quality may also contribute. Sperm DNA fragmentation testing is not yet part of the routine recurrent loss workup.
Unexplained RPL (50%)
After a complete evaluation, no identifiable cause is found in approximately half of couples. The prognosis in these cases is relatively good, with a 60 to 70% chance of live birth in the next pregnancy with supportive care alone.
<image>Pie chart showing the etiologic distribution of recurrent pregnancy loss: chromosomal/genetic factors (50-60% of sporadic losses, 3-5% parental), uterine anatomic (10-15%), antiphospholipid syndrome (5-15%), endocrine (5-10%), thrombophilia (5%), and unexplained (50% after complete evaluation)</image>
Evaluation Algorithm
Recommended for All RPL Patients
Parental karyotyping of both partners should be performed, or targeted testing if a prior products of conception analysis revealed a balanced rearrangement. Chromosomal analysis (microarray or karyotype) should be obtained on products of conception from any future loss. The uterine cavity should be evaluated with transvaginal ultrasound as a baseline, followed by saline infusion sonohysterography or HSG for cavity detail. MRI is indicated if a Mullerian anomaly is suspected, and hysteroscopy provides definitive diagnosis and treatment. An antiphospholipid antibody panel including lupus anticoagulant, anticardiolipin IgG and IgM, and anti-beta-2-glycoprotein I IgG and IgM should be ordered, with the requirement that positive results be confirmed on a second occasion at least 12 weeks later. Thyroid function testing includes TSH, free T4, and TPO antibodies. Hemoglobin A1C or fasting glucose is checked if diabetes is suspected. Prolactin is measured if there is oligomenorrhea or galactorrhea.
Consider Based on Clinical Context
A thrombophilia panel is indicated only if there is a personal or family history of venous thromboembolism. Ovarian reserve testing with AMH and antral follicle count is relevant for women of advanced maternal age. Sperm DNA fragmentation testing is not yet standard. Endometrial biopsy for chronic endometritis, using CD138 staining for plasma cells, may be considered.
<image>Step-by-step RPL evaluation algorithm showing the recommended workup: parental karyotyping and POC analysis, uterine cavity assessment with SIS/HSG and hysteroscopy, antiphospholipid antibody panel (with requirement for repeat testing at 12 weeks), thyroid panel with TPO antibodies, and metabolic screening, with clear action steps for each abnormal result</image>
Treatment
Antiphospholipid Syndrome
Treatment with low-dose aspirin (81 mg daily) plus prophylactic heparin (unfractionated or low-molecular-weight) dramatically improves outcomes. Aspirin is started preconceptionally, and heparin is added when pregnancy is confirmed. Unfractionated heparin is dosed at 5,000 to 10,000 units subcutaneously twice daily, or enoxaparin 40 mg subcutaneously daily can be used. Heparin is continued through delivery and stopped before delivery or epidural placement. Postpartum anticoagulation is continued for 6 weeks given the elevated thrombotic risk. Treatment reduces pregnancy loss rates from approximately 75% to 20 to 30%.
Uterine Anomalies
Hysteroscopic metroplasty (septal resection) for a uterine septum reduces miscarriage rates from approximately 60% to 15%. Submucosal fibroids are treated with hysteroscopic myomectomy. Asherman syndrome is managed with hysteroscopic adhesiolysis followed by post-operative estrogen therapy. Endometrial polyps are removed by hysteroscopic polypectomy.
Thyroid Disorders
Overt hypothyroidism should be treated with the goal of maintaining TSH below 2.5 mIU/L in the first trimester. Subclinical hypothyroidism with positive TPO antibodies is a reasonable indication for levothyroxine supplementation, given the low risk and potential benefit.
Chromosomal Rearrangements
Couples with parental balanced chromosomal rearrangements should receive genetic counseling. Options include natural conception with prenatal diagnosis through CVS or amniocentesis, IVF with preimplantation genetic testing for structural rearrangements (PGT-SR), or use of donor gametes. PGT-SR selects chromosomally balanced embryos for transfer.
Progesterone Supplementation
The PRISM trial (2019) evaluated vaginal micronized progesterone (400 mg twice daily) started at the first sign of bleeding in women with a history of recurrent loss. Overall results showed a modest but non-significant benefit, though subgroup analysis suggested benefit in women with three or more prior losses. The earlier PROMISE trial (2015) found no significant benefit of progesterone versus placebo in the first trimester for women with unexplained recurrent loss. The current stance is that progesterone supplementation is reasonable to offer in women with three or more prior losses, given the low risk and potential benefit.
Unexplained RPL
Supportive care and close follow-up, sometimes called "tender loving care," form the foundation of management. This includes early ultrasound confirmation of viability, frequent reassurance visits, and psychological support. Dedicated early pregnancy clinics have achieved a 75% live birth rate with this approach alone. Empiric treatments lacking evidence, such as IVIG, intralipids, paternal lymphocyte immunotherapy, and corticosteroids, are not recommended.
Clinical Pearls
Antiphospholipid syndrome is the most important treatable cause of recurrent pregnancy loss. Testing should be performed in all patients, and laboratory criteria require confirmation 12 weeks apart.
Half of recurrent pregnancy loss remains unexplained after a complete evaluation. Patients should be counseled that the prognosis is still good, with a 60 to 70% chance of live birth in the next pregnancy with supportive care alone.
Parental karyotyping detects balanced rearrangements in 3 to 5% of couples with recurrent loss. This finding has implications for genetic counseling and may lead to IVF with PGT-SR.
Products of conception chromosomal testing on a subsequent loss can provide valuable information and may avoid unnecessary invasive workup if the loss was aneuploid.
The uterine septum is the most surgically correctable anatomic cause of recurrent pregnancy loss. Hysteroscopic resection significantly reduces loss rates.
Routine thrombophilia panels should not be ordered for recurrent loss unless there is a personal or family history of venous thromboembolism.
Immune testing (NK cells, cytokine panels) and immune therapies (IVIG, intralipids) are not supported by evidence and should not be offered.
<image>Comparison of treatment options and evidence levels for RPL by etiology: APS (aspirin + heparin, strong evidence), uterine septum (hysteroscopic resection, moderate evidence), parental translocation (PGT-SR, moderate evidence), thyroid (levothyroxine, moderate evidence), and unexplained RPL (supportive care and progesterone, emerging evidence from PRISM trial)</image>
References
- ACOG Practice Bulletin No. 200: Early Pregnancy Loss (2018)
- ASRM Practice Committee Opinion. Evaluation and treatment of recurrent pregnancy loss. Fertil Steril. 2012;98:1103-1111
- Coomarasamy A et al. (PRISM trial). A randomized trial of progesterone in women with bleeding in early pregnancy. N Engl J Med. 2019;380:1815-1824
- Coomarasamy A et al. (PROMISE trial). Micronized vaginal progesterone to prevent miscarriage. N Engl J Med. 2015;373:2141-2148
- Miyakis S et al. International consensus statement on an update of the classification criteria for definite antiphospholipid syndrome. J Thromb Haemost. 2006;4:295-306
- ESHRE Guideline Group on RPL. Recurrent pregnancy loss: ESHRE guideline. Hum Reprod Open. 2022
- RCOG Green-top Guideline No. 17: The Investigation and Treatment of Couples with Recurrent First-Trimester and Second-Trimester Miscarriage (2011)
