Migraine is a common cause of headaches, affecting around 1 in 7 people. It is more common in women and particularly affects those under 50, meaning it is important to understand its impact on pregnancy.
Several conditions are more common in people with migraine, including anxiety, depression, chronic pain conditions and epilepsy. Migraine is often classified by whether the person experiences aura or not (where there are warning symptoms, such as flashing lights, before the headache begins). People who get migraine with aura are a higher risk of having cardiovascular disease and strokes. It has also been linked to a higher risk of pregnancy complications such as pre-eclampsia and low birth weight.
Migraine can be treated with preventative medicines to reduce the frequency of headaches and with medicines that alleviate symptoms such as pain and nausea. More research is needed into the safety of these medicines in pregnancy.
The purpose of this study is to look at what percentage of pregnant women experience migraines and whether this has changed over the past two decades. It will also look at which medications are prescribed in pregnancy for women with migraine. It will also look at whether having migraine, being treated for migraine, and having migraine with aura effects the chances of having pregnancy complications. This will help further our understanding of how migraine affects pregnancy and will guide future research into 1) which people with migraine are most at risk in pregnancy and 2) the safety of drugs used for migraine.
The aims of this study are to estimate the trends in migraine prevalence and treatment patterns in women of reproductive age and pregnant women over the past two decades, as well as to estimate the risk of adverse pregnancy outcomes in treated and untreated women with migraine and those with and without aura.
A retrospective cohort study of all eligible women in CPRD aged between 15 and 50 will be conducted to estimate the annual prevalence and incidence rates of migraine. Using the CPRD pregnancy register, annual cohorts of pregnant women will be established to estimate annual prevalence of migraine during pregnancy.
In the annual cohorts of pregnant women with migraine, the proportion prescribed drugs for the treatment of migraine will be calculated, stratified by acute drugs (pain relief, antiemetics, combinations, triptans) and prophylactic drugs (beta blockers, topiramate, amitriptyline, candesartan, sodium valproate, flunarizine, pizotifen, calcitonin gene-related peptide inhibitors).
A retrospective age-matched controlled cohort study of pregnant women with and without migraine will be conducted to estimate the effect of migraine on pregnancy-related outcomes including miscarriage, pre-eclampsia, gestational diabetes, preterm birth, stillbirth, congenital anomalies and perinatal mental illness using logistic regression.
The risk of developing various pregnancy-related outcomes will also be examined for women with treated and untreated migraine and those with and without aura.
The main data source for this study will be: CPRD, the CPRD pregnancy register with mother baby link, for outcomes better recorded in secondary care, linked HES data will be used. ONS death registration data and patient level IMD will also be used.
This study will further our understanding of the risk of adverse pregnancy outcomes in women with migraine. It will inform further studies into the safety of drugs used for migraine and potential risk stratification models for adverse pregnancy outcomes for women with migraine.
• Prevalence and incidence trends of migraine in women of reproductive age and during pregnancy
• Common prescriptions among pregnant women with migraine
• Risk of adverse pregnancy outcomes (see below) among
o pregnant women with migraine, compared to pregnant women without migraine
o between treated and untreated women with migraine
o pregnant women with migraine with and without the presence of aura
The outcomes are grouped into the following four categories:
(1) Antenatal
Antenatal outcomes are outcomes that occurred from conception to before delivery. Examples include miscarriage, gestational hypertension, pre-eclampsia, gestational diabetes, obstetric cholestasis, foetal growth restriction, venous thromboembolism and cardiovascular outcomes. (using ICD-10 codes within HES data and Read codes within primary care)
(2) Peripartum
Peripartum outcomes are outcomes that occur around the time of delivery. Examples include mode of delivery (spontaneous vaginal, instrumental vaginal, elective caesarean, emergency caesarean), preterm delivery, small for gestational age, perineal trauma, stillbirth, neonatal death, and maternal death. (HES data /ONS Death Registration data within 28 days of mother’s delivery date; Baby’s patient ID will be identified using MBL data)
(3) Postnatal and long-term
Postnatal outcomes are outcomes that occurred beyond the episode of delivery, here we include long-term outcomes that are beyond the 42 days of postnatal period. Examples for mothers include new onset type 2 diabetes mellitus and new onset chronic kidney disease. Examples for children include congenital anomaly and neurodevelopmental disorder. (Read Codes within primary care)
(4) Perinatal mental health
Perinatal mental health outcomes are mental health outcomes that occurred after the pregnancy has ended. Examples include postnatal depression, puerperium psychosis, suicide attempts and self harm. (Read Codes within primary care)
Katherine Phillips - Chief Investigator - University of Birmingham
Katherine Phillips - Corresponding Applicant - University of Birmingham
Francesca Crowe - Collaborator - University of Birmingham
Krishnarajah Nirantharakumar - Collaborator - University of Birmingham
CPRD Mother-Baby Link;HES Admitted Patient Care;ONS Death Registration Data;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation;Pregnancy Register;CPRD Aurum Mother-Baby Link;CPRD Aurum Pregnancy Register;CPRD GOLD Mother-Baby Link;CPRD GOLD Pregnancy Register