Preterm preeclampsia is a severe condition for both the mother and the fetus. Currently, the only treatment available to stop disease progression is termination/delivery of the fetus and placenta. Therefore, preterm preeclampsia carries the highest rates of neonatal morbidity and mortality due to iatrogenic preterm birth. There is evidence suggesting metformin, a drug commonly used to treat diabetes in and outside pregnancy, may be able to counter the pathophysiology of preeclampsia, raising the possibility that it could be used to treat the condition. This multi centre double blind randomised controlled trial aims to investigate if metformin can prolong gestation, lower neonatal length of stay and increase birthweight in a Nordic setting.

Preeclampsia is globally responsible for 60,000 maternal deaths per year, and far greater numbers of fetal losses. Preterm preeclampsia is a severe variant with the highest rates of neonatal morbidity and mortality due to iatrogenic preterm birth (clinicians are forced to deliver the baby preterm for maternal or fetal health reasons).

There is preclinical evidence suggesting metformin, a drug commonly used to treat diabetes in and outside pregnancy, may be able to counter the pathophysiology of preeclampsia, raising the possibility that it could be used to treat the condition.

Previous research from the Preeclampsia Intervention 2 trial (PI2) show that metformin was able to delay delivery in early preterm preeclampsia. Metformin extended release (ER) was associated with a median 7.6-day prolongation of pregnancy (geometric mean ratio (GMR) 1.39 (95% CI 0.99 to 1.96) P=0.057).Trends towards increased birthweight (mean difference 110gm (95%CI -80 to 300), a decreased length of stay at the neonatal intensive care unit (median difference 5.0 days less; GMR 0.86, 95% CI 0.62 to 1.2) and a shorter period of admission in any neonatal ward (median difference 12.0 days less; GMR 0.82, 95% CI 0.57 to 1.18) in the metformin ER group were found. Importantly, while gastrointestinal side effects were common, no serious adverse events related to trial medications were observed.

The PI 2 trial has shown that metformin may be a disease modifying treatment for preterm preeclampsia. The trial is being repeated in a larger scale in the PI3 trial in South Africa to also assess neonatal outcomes. In the Nordic countries, the demographics of the population are different and expectant management of preeclampsia allows for the women to reach 37 weeks of gestation as opposed to 34 weeks of gestation in the PI2 trial. This trial aims to investigate if metformin can prolong gestation, lower neonatal length of stay and increase birthweight in a Nordic setting. Follow up of mothers and children will be carried out two years post partum.

Inclusion Criteria:

• A diagnosis of preeclampsia (defined as hypertension in combination with significant proteinuria (albumin/creatinine ratio >8 mg/mmol, protein/creatinine ratio>30 mg/mmol or >2+ protein on a urinary dipstick) has been made by the attending clinician
• The managing clinicians have made the assessment to proceed with expectant management.
• The subject has given written consent to participate in the study.
• The woman must be 18 years of age or older
• The gestational age is between 22+0 weeks to 33+6 weeks with a viable fetus
• The woman carries a singleton pregnancy

Exclusion Criteria:

• Contraindications to treatment with metformin as outlined in SmPC
• Contraindications for expectant management of preeclampsia such as an immediate indication for delivery according to SFOG guidelines for preeclampsia (https://www.sfog.se/media/338533/pe-riktlinje-230214.pdf).
• Type 1 Diabetes Mellitus
• Current use of metformin
• Known or suspected allergies against metformin
• Reluctance or language difficulties that result in difficulty understanding the meaning of study participation
• Unable to understand the informed consent process
• Previous participation in the study
• Established fetal compromise that necessitates imminent delivery (including planned delivery after 48 hours of corticosteroid treatment). This will be decided by the clinical team before expectant management is offered to the patient.
• Suspicion of a major known fetal anomaly or malformation.
• Renal disease or dysfunction, suggested by a creatinine level greater than or equal to 125 µmol/L or rapidly declining renal function
• Known acute or chronic metabolic acidosis, including diabetic ketoacidosis
• Not suitable for inclusion by the opinion of the investigator

We plan to share data with similar ongoing or planned trials in South Africa and The Netherlands.