The PIONEER Study - A study to investigate whether taking the medication Pravastatin reduces the number of babies born too early (preterm, i.e., before 37 weeks of pregnancy) and, if so, how it works in the body to do this.

INTERVENTION: Participants will be randomised in a 1:1 ratio to receive either Pravastatin or placebo. Randomisation will be performed via the trial database using Sealed Envelope. Participants randomised to the intervention group will receive Pravastatin 20mg and participants randomised to the placebo group will receive a matched tablet with no active substance. Both will be taken orally once daily by participants, from between 16+0 and 20+0 weeks gestation until 37+0 weeks gestation. Treatment may be stopped earlier (reasons are detailed in the protocol). All participants will be followed up until birth or loss of pregnancy. Participants recruited in the first 18 months of the trial will be asked to complete a questionnaire when their child is two years old. CONDITION: Intermediate or high risk for preterm birth ; Pregnancy and Childbirth PRIMARY OUTCOME: Gestational age, in days, at birth, measured using patient records. SECONDARY OUTCOME: 1. Maternal and neonatal secondary outcomes:; Maternal secondary outcomes: maternal mortality; antenatal infection requiring antibiotics; intrapartum infection requiring antibiotics; development of pre‐eclampsia; PPROM; harm to mother from intervention; cervical cerclage; progesterone use; shortest cervical length measured. ; Neonatal secondary outcomes: Premature birth (categorising <37 weeks' gestation, and <34 weeks gestation); Apgar scores at 1, 5, and 10 minutes of age; admission to Neonatal Intensive Care Unit (NICU); birthweight; early neurodevelopmental morbidity; gastrointestinal and respiratory morbidity; neonatal mortality; infection requiring antibiotics; need for respiratory support; harm to offspring from intervention. Collected from hospital databases following birth and discharge from hospital admission.; 2. Mechanism of action of Pravastatin, evaluated using mechanistic studies to assess maternal:; 2.1. Cervicovaginal fluid concentrations of inflammatory markers of interest, including IL‐8, IL‐6, IL‐2, MBL, IgG1, IgG3, C3b and C5a; ; 2.2. Vaginal microbiota profile;; 2.3. Serum lipid profile: very‐low‐density lipoprotein (VLDL), intermediate‐density lipoprotein (IDL), low‐density lipoprotein (LDL) and high‐density lipoprotein (HDL) assessed via NMR metabolomics; and, ; 2.4. Stool microbiota profile and metabolomics profile.; 2.5. Maternal blood inflammatory profile.; Samples collected as baseline, 24 weeks' gestation and 28 weeks' gestation.; 3. For the offspring of pregnancies for those participants recruited during the first 18 months of the trial only. Assessment of child's cognitive and language development using the Parent Report of Children’s Abilities‐Revised (PARCA‐R) questionnaire. Questionnaire completed at 2 years corrected age for child. INCLUSION CRITERIA: 1. Pregnant people with a singleton pregnancy identified as being at high or intermediate risk for PTB according to criteria detailed in the Saving Babies’ Lives Care Bundle (V3), where: 1.1. High risk ‐ at least one of the following: 1.1.1. Previous mid‐trimester loss >16 weeks' gestation; 1.1.2. Previous PTB <34 week's gestation; 1.1.3. Previous Preterm Premature Rupture of Membranes (PPROM) <34 weeks’ gestation; 1.1.4. Previous use of cervical cerclage; 1.1.5. Known uterine structural variant; 1.1.6. Intrauterine adhesions; 1.1.7. History of trachelectomy (for cervical cancer). OR 1.2. Intermediate risk ‐ at least one of the following: 1.2.1. Previous birth by caesarean section at full dilatation; 1.2.2. History of significant excision of cervical cells (e.g., Large Loop Excision of Transformation Zone (LLETZ) where >15mm depth removed, or >1 LLETZ procedure carried out or cone biopsy). 2. Between 16+0‐ and 20+0 weeks’ ges