Recurrent pregnancy loss (RPL) defined as 3 or more pregnancy losses affects approximately 3% of couples trying to achieve parenthood. Most cases of RPL are unexplained and have no effective treatment to improve the chance of a live birth. Exciting indications for using Hydroxychloroquine (HCQ) include: Malaria profylaxis and treatment, systemic and discoid lupus erythematosus (SLE) and rheumatoid athritis (RA). HCQ has been reported to have the following properties (anti-thrombotic, vascular-protective, immunomodulatory, improving glucose tolerance, lipid-lowering, and anti-infectious).

There is no data concerning the benefit of HCQ in RPL. Administration for other indications provides extensive safety data during pregnancy.

This study has the potential to establish support for a new treatment option for unexplained RPL.

Inclusion Criteria:

1. ≥ 4 confirmed consecutive pregnancy losses prior to gestational age 22+0 in women with unexplained RPL
2. ≥ 3 confirmed consecutive pregnancy losses prior to gestational age 22+0 in women with unexplained RPL with minimum one second trimester loss.

Exclusion Criteria:

1. Age below 18 years or above 39 at inclusion
2. Abnomal uterine anatomi at hysterosalpingography/hysteroscopy or hydrosonography
3. Chromosomal abnormalities within the couple
4. Menstrual cycle below 23 days or above 35 days
5. Lupusantikoagulans positivity or immunoglobulin (Ig)G/IgM anticardiolipinantibodies (≥10 GPL kU/l at Rigshospitalets Laboratorium) or plasma homocystein ≥25 mikrogr./l at repeated measurement with 12 weeks interval.
6. HIV or Hepatitis B or C positive
7. Psoriasis, retinopathy og serious imparied hearing (Contraindications for HCQ)
8. Chronic disease that lead to intake of immunemodulatory drugs or potentially pregnancy toxic agents
9. Hemoglobin ≤ 6.5 mmol/L, leukocytes <3.5 E9/L, platelets <145 E9/L at inclusion
10. Previous treatment with HCQ in pregnancy
11. >1previous live birth
12. previous participation in this trial