Prednisolone Administration in Patients With Unexplained REcurrent MIscarriages

Inclusion Criteria: In order to be eligible to participate in this study, a subject must meet all of the following criteria: * Unexplained recurrent pregnancy loss: defined as the loss of ≥2 pregnancies, without any known cause for RM (parental chromosomal abnormalities, uterine anomalies, acquired or hereditary thrombophilia, endocrine diseases (such as hypothyroidism or diabetes)). * The miscarriages include: * all consecutive or non-consecutive pregnancy losses before the 24th week of gestation verified by ultrasonography or uterine curettage and histology * non-visualized pregnancies (including biochemical pregnancy losses and/or resolved and treated pregnancies of unknown location), verified by positive urine or serum hCG Ectopic and molar pregnancies are not included * Age 18 - 39 years at randomization (likelihood of miscarriages due to chromosomal aberrations is higher when age \> 39 years. Such miscarriages are unlikely to be pre-vented by prednisolone therapy) * Conception confirmed by urinary pregnancy test, with estimated gestational age ≤ 7weeks * Willing and able to give informed consent in English or Dutch (IC) Exclusion Criteria: A potential subject who meets any of the following criteria will be excluded from participation in this study: * Any of the following diagnosis for the recurrent miscarriages * Antiphospholipid syndrome (lupus anticoagulant and/ or anticardiolipin anti-bodies and/or beta-2 glycoprotein \[IgG or IgM) * Congenital uterine abnormalities (as assessed by 2D or 3d ultrasound, hys-terosonography, hysterosalpingogram or hysteroscopy) * Abnormal parental karyotype * Instable or exacerbation of auto-immune diseases such as diabetes, thyroid disease, inflammatory bowel diseases or SLE * Inability to conceive within 1 year of recruitment * Current treatment with systemic prednisolone or other immune suppressive medication (for any indication) * Previous enrolment in the PREMI trial * Enrolment in any other trial that studies the effectiveness of an intervention on RM * Contraindications to prednisolone use: * Known allergy for prednisolone * Acute bacterial infection or parasite infection * Active COVID infection * Systemic sclerosis * Ulcus ventriculi or ulcus duodeni in medical history * Obesity with BMI \>40 * Some drugs are known to interact with Prednisolone, and thus women on the following drugs are not eligible to take part in the PREMI trial: * Enzyme inducers, such as carbamazepine, fenobarbital, fenytoïne and ri-fampicine * CYP3A inhibitors, such as Cobicistat or Ritonavir * Cyclosporine * Digoxin * Vaccination (with inactivated virus or bacteria) during prednisolone use is possibly less effective