Migraine headaches are common and can cause difficulties with work and daily activities, reducing the quality of life for migraine sufferers. An estimated 17-24% of women aged 18-39 experience migraines.(1,2) Hypertensive Disorders of Pregnancy (HDOP) refer to conditions characterized by high blood pressure during pregnancy, including gestational hypertension, preeclampsia, and eclampsia. HDOP can lead to pre-term birth, admission to neonatal intensive care, and death of the foetus or mother. Individuals who suffer from migraines may have abnormalities in blood vessel constriction, inflammation, or blood clotting, which may also increase their risk of HDOP. Although some studies have shown that migraine sufferers have double or triple the risk of HDOP compared to those who do not suffer from migraines, these studies tend to be small and outdated. More recent, larger studies have shown smaller increases in HDOP risk among migraine sufferers. This study will help to clarify the extent to which migraines are associated with the risk of hypertensive disorders of pregnancy. Results from this study will help clinicians in the UK better understand migraines as a potential risk factor for HDOP and provide appropriate education and monitoring, potentially improving the health of mother and baby. In addition, individuals who experience HDOP are more likely to be diagnosed with hypertension later in life (12,13), so increased HDOP research may also lead to increased awareness and vigilance in preventing future health complications.
Migraine is a neurovascular disorder common in the reproductive aged population, with an estimated prevalence of 17% in women ages 18-29 years and 24% in women ages 30-39 years.(1,2) Migraines can have profound impacts on daily activities and work, can affect quality of life, and are the seventh-highest specific cause of disability globally.(3,4) Hypertensive disorders of pregnancy (HDOP) include gestational hypertension and pre-eclampsia/eclampsia, and are associated with foetal death, preterm birth, maternal mortality, and neonatal intensive care admission.(5) Although there have been several studies on the association between migraines and hypertensive disorders of pregnancy, much of the existing literature is outdated, relies on inconsistent exposure definitions, and focused on pre-eclampsia rather than the spectrum of HDOP severity.(6,7)
The primary aim of this study is to evaluate the association between pre-pregnancy migraine and hypertensive disorders of pregnancy. We plan to conduct a cohort study for this analysis. First, we will select all deliveries from 1993-2020 with at least 24 months of data in the CPRD prior to the individual’s first delivery date. We will categorize deliveries to individuals with migraines prior to the estimated date of conception (delivery date – 280 days) as exposed. We will use log binomial regression with robust standard errors to estimate crude and adjusted risk ratios with 95% confidence intervals of HDOP among deliveries to individuals with pre-pregnancy migraines, compared to those without migraines, accounting for non-independence among individuals with more than one delivery. Additionally, the study will examine the association between migraines and HDOP for migraines treated with prescription medication vs. untreated migraines and migraines which resolve vs. persist beyond the first trimester of pregnancy.
The main outcome of interest in this study is hypertensive disorders of pregnancy (gestational hypertension and pre-eclampsia/eclampsia). Hypertensive disorders of pregnancy will be analysed as a binary composite outcome and categorically by severity (no hypertension, gestational hypertension, and pre-eclampsia/eclampsia). Read codes to select cases are provided in appendix 1.
Susan Jick - Chief Investigator - BCDSP - Boston Collaborative Drug Surveillance Program
Holly Crowe - Corresponding Applicant - Boston University School of Public Health