Tests a folate supplement in pregnant people with high blood pressure
Tests a folate supplement against a placebo in pregnant adults with high blood pressure.
Plain-language title generated from the registry record
Registry title: Clinical Antenatal Randomised Study to CharactErise Key Roles of TetrahydroFOLate in HyperTensive Pregnancies
Key facts
- Where
- Oxford, United KingdomSee the 2 sites
AI summary: who the study is looking for
From the trial's eligibility criteria. Machine-read from the registry text on this page, so it can be wrong. The registry text below and the trial team decide who can take part.
The trial is looking for pregnant women, either with pre-eclampsia before 34 weeks or with normal blood pressure. It studies a folate supplement and blood vessel function.
- Age
- Over 18 and up to 45 years
- Sex
- Women only
- Disease stage
- Pre-eclampsia group: diagnosed at less than 34 weeks of pregnancy within the last 48 hours, with no birth planned within the next week. Comparison group: normal blood pressure (below 140/90) throughout pregnancy.
- Earlier treatment
- Pre-eclampsia group: no folate supplement above 400mcg in the third trimester, and no proton pump inhibitors or anti-epileptic drugs. Comparison group: no beta blockers such as atenolol or equivalent.
- Biomarker or test result
- Comparison group: SFlt/PIGF ratio below 35. Both groups: vitamin B12 level not below 148 pmol/L (pre-eclampsia group).
Main reasons for not taking part
- Heart problems such as uncontrolled arrhythmia, unstable angina, heart failure or valve disease
- Existing long-term kidney disease
- Baby with any known trisomy, a congenital heart defect, a known infection or high risk of heart disease
- Known severe anaemia in the baby
- Cannot take folate supplements (pre-eclampsia group)
This trial only enrols pregnant participants. The registry sentence this rests on: Normotensive, blood pressures <140/90 throughout antenatal period
Read by machine on 9 November 2026.
Could this be for you?
Answer for yourself. This is not a decision: only the study team can say whether you can take part.
- Are you between 18 and 45 years old?
Source: NCT05434195, who can take part
Where in United Kingdom
- Cardiovascular Clinical Research FacilityOxford, United KingdomTaking people
- Oxford University Hospitals NHS Foundation TrustOxford, United KingdomTaking people
Questions to ask the study team
- How often do I need to come in, and for how long each time?
- Are travel costs paid?
- Can I keep my own doctor?
- What happens if I want to stop?
Trial details
- Who runs it
- University of Oxford
- Trial code
- NCT05434195
- Record updated
- 29 April 2026
- Original description
Study backgroundRead full original descriptionShow less
Clinical Antenatal Randomised Study to CharactErise Key Roles of TetrahydroFOLate in HyperTensive Pregnancies (CAREFOL-HT)
Study background
High blood pressure during pregnancy is a worldwide health problem that can be dangerous to mothers and commonly causes premature birth and small babies. There is also growing evidence that mothers who suffer from high blood pressure in pregnancy, and their babies, have a higher risk of high blood pressure and cardiovascular disease later in life. Previous studies have revealed detrimental changes in the structure and function of the heart and blood vessels of mothers, and their babies, who experience this common complication. These changes may explain their increased risk of later disease. The investigators have also learned through previous studies that tetrahydrobiopterin (BH4), a molecule that has a role in blood vessel health, plays an important role in stabilising blood vessel function. Lower levels of BH4 are evident in both the placenta and the umbilical cord from mothers with high blood pressure. We, therefore, want to investigate how closely BH4 levels are related to clinical features of pre-eclampsia and whether altering levels of BH4, using a nutritional supplement, improves features of the disease such as blood vessel function. To do this, the investigators need to compare the levels of BH4 between mothers with pre-eclampsia, those taking the supplement and those without pre-eclampsia. The investigators also compare how the heart and blood vessels look and function in these groups using ultrasound methods, including echocardiography and fetal sonography.
Study objectives
CAREFOL-HT will assess how levels of BH4 differ in pregnant women with high blood pressure and if this is reflected in functional changes in the heart and blood vessels of these women. The investigators will also determine whether changing levels of BH4, using a tetrahydrofolate supplement (5-MTHF), changes blood vessel function.
Inclusion: Diagnosed with preeclampsia, as defined in Section 8.1, at <34 weeks' gestation within the last 48 hours and with no delivery planned within the next week; Receiving antenatal care in the John Radcliffe Hospital; Participant is willing and able to give informed consent for participation in the study; Age >18 and ≤45 years; Participant is willing and able to give informed consent for participation in the study; Age >18 and ≤45 years; Normotensive, blood pressures <140/90 throughout antenatal period; Less than 2 moderate risk factors for hypertensive disease in pregnancy according to the NICE guideline for management of hypertension in pregnancy; SFlt/PIGF ratio <35.
Exclusion: Intake of either proton pump inhibitors or anti-epileptic drugs; History of cardiac impairments including uncontrolled arrhythmia, unstable angina, decompensated congestive heart failure or valve disease; History of preexisting chronic renal disease; Fetus with congenital heart defect; Fetus at a high risk of heart disease; Known infection of fetus; Diagnosis of hypertensive disorder of pregnancy; History of cardiac impairments including uncontrolled arrhythmia, unstable angina, decompensated congestive heart failure or valve disease; History of preexisting chronic renal disease Fetal; Fetus with congenital heart defect; Fetus at a high risk of heart disease; Known infection of fetus; The participant may not enter the study if ANY of the following apply:; Maternal; Contraindication to taking folate related supplements; Folate supplementation in excess of 400mcg in the third trimester; Low vitamin B12 levels (<148 pmol/L); Organ dysfunction Fetal; Any known trisomy; Known severe anaemia; The participant may not enter the study if ANY of the following apply:; Maternal; Use of beta blockers such as atenolol or equivalent; Any known trisomy; Known severe anaemia.