Does supplementation of extra Magnesium daily to first time pregnant healthy women prevent blood pressure increase during pregnancy?

INTERVENTION: After oral and written consent, participants are randomised in a computerised double‐blind procedure to receive either Mg (400 mg Magnesium Extra, Diasporal®) or placebo, taken daily. The code is not broken until all participants have given birth. Data is collected throughout pregnancy and from medical records after delivery. There is no further patient follow up after delivery. Blood samples are collected at gestational weeks 12–14 and 35 for analysis of IL‐6, CRP, urate, cystatin C, Mg, Ca, albumin, creatinine and glomerular filtration rate (GFR). Blood pressure (BP) is measured at the ACU at 2–3 week intervals throughout the pregnancy, with the women seated with arm‐ and backrest support, down to Korotkoff V with a manual sphygmomanometer. BP data registered at the ACU and labour ward are collected from medical records. Records are obtained on gestational length at birth, labour outcomes including excessive bleeding >1000 ml, instrumental delivery, duration of active labour, and fetal outcomes including Apgar score at five minutes, pH in the arterial umbilical cord, birth weight and need of care at a neonatal intensive care unit (NICU). CONDITION: Blood pressure in pregnancy ; Pregnancy and Childbirth ; Blood pressure in pregnancy PRIMARY OUTCOME: Blood pressure is measured using manual sphygmomanometer at 2‐3 week intervals throughout the pregnancy, and obtained from medical records at labour. SECONDARY OUTCOME: 1. Biomarkers for hypertensive disorders ( IL‐6, CRP, urate, cystatin C, Mg, Ca, albumin, creatinine and glomerular filtration rate (GFR) are analysed from blood samples at gestational weeks 12‐14 and 35.; 2. Labour and foetal outcomes (gestational length at birth, excessive bleeding >1000 ml, instrumental delivery, duration of active labour, Apgar score at five minutes, pH in the arterial umbilical cord, birth weight and need of care at a neonatal intensive care unit) are collected from medical records after delivery. INCLUSION CRITERIA: 1. Nulliparity 2. No regular medication 3. Normotension 4. Singleton pregnancy 5. Maternity age >18 years and < 40 years