What is the recommended treatment for a pregnant woman with a history of recurrent miscarriage?

Treatment for Recurrent Abortion in Currently Pregnant Women

For a currently pregnant woman with recurrent miscarriage, the recommended treatment depends critically on whether she has antiphospholipid antibody syndrome (APLA): if APLA-positive, use prophylactic low-molecular-weight heparin (LMWH) combined with low-dose aspirin (75-100 mg/day) starting immediately and continuing until at least 34 weeks; if APLA-negative or unexplained recurrent pregnancy loss, progesterone supplementation (such as 400 mg micronized vaginal progesterone twice daily) should be considered, especially if she presents with bleeding, though aspirin and/or heparin should NOT be given for unexplained cases. 1, 2

Immediate Assessment Required

First, determine the underlying cause through targeted screening:

• Screen for antiphospholipid antibodies (lupus anticoagulant and anticardiolipin antibodies) if not already done 1
• Check thyroid function tests and thyroid peroxidase (TPO) antibodies 2
• Assess for diabetes and ensure glycemic control if present 3

Treatment Algorithm Based on Etiology

If APLA Syndrome is Confirmed (≥3 prior losses)

This is the only evidence-based treatment with strong recommendations:

• Start prophylactic or intermediate-dose unfractionated heparin OR prophylactic LMWH combined with low-dose aspirin (75-100 mg daily) 1
• Continue from positive pregnancy test until at least 34 weeks of gestation 2
• LMWH is preferred over unfractionated heparin for ease of use and safety profile 1
• This combination therapy has Grade 1B evidence supporting improved live birth rates 1

If Unexplained Recurrent Pregnancy Loss (No APLA)

Critical distinction: Do NOT use aspirin and/or heparin - the guidelines explicitly recommend AGAINST antithrombotic prophylaxis in women with two or more miscarriages without APLA or thrombophilia (Grade 1B) 1

Instead, consider:

• Progesterone supplementation if she presents with bleeding in early pregnancy: 400 mg micronized vaginal progesterone twice daily from time of bleeding until 16 weeks of gestation (Grade B) 2
• Recent evidence suggests progesterone may be helpful when started in the luteal phase and continued through early pregnancy 4
• However, a 2025 Cochrane review found that for unexplained RPL, progesterone probably results in little to no effect on miscarriage rates (moderate-certainty evidence) 5

If Inherited Thrombophilia is Present

Do NOT use antithrombotic prophylaxis - guidelines suggest against using antithrombotic prophylaxis for women with inherited thrombophilia and history of pregnancy complications (Grade 2C) 1

The evidence shows only weak associations between inherited thrombophilias and recurrent miscarriage 2

Supportive Care Measures (Essential for All)

Provide dedicated supportive care - this is strongly recommended regardless of etiology:

• Enroll in a dedicated recurrent miscarriage clinic if available 2
• Provide trauma-informed care and emotional support 4
• Early pregnancy assessment with close monitoring 4
• Shared decision-making throughout pregnancy 4

Lifestyle Modifications to Implement Now

• Maintain BMI between 19-25 kg/m² 2
• Complete smoking cessation 2
• Limit alcohol consumption 2
• Limit caffeine to less than 200 mg/day 2

Important Caveats

Avoid these common pitfalls:

1. Do not empirically treat with heparin/aspirin without confirmed APLA syndrome - this is explicitly recommended against and wastes resources while potentially causing harm 1

2. Do not screen for or treat based on inherited thrombophilias - routine testing for protein C, antithrombin deficiency, Factor V Leiden, or MTHFR mutation is not recommended as these have weak associations with RPL 2

3. Do not use immunological therapies (HLA testing, cytokine panels, natural killer cell testing) outside research contexts 2

4. Thyroxine supplementation is NOT recommended for euthyroid women with TPO antibodies (Grade A) 2

Divergent Evidence to Note

There is tension in the literature regarding progesterone therapy. The 2023 BJOG guideline 2 suggests considering progesterone for women presenting with bleeding (Grade B), and the 2025 Thai recommendations 6 support oral dydrogesterone for unexplained RPL. However, the 2025 Cochrane review 5 found only moderate-certainty evidence of little to no benefit. The most pragmatic approach is to offer progesterone when bleeding occurs in early pregnancy, as this represents the highest-risk scenario where potential benefit may outweigh minimal harm.

The strongest evidence remains for APLA syndrome treatment with heparin plus aspirin - this is the only intervention with Grade 1B evidence for improving outcomes 1.