PJ was responsible for the study design, epidemiological enquiry, data collection, statistical calculations, and drafting of the manuscript.
However, the non-responder study had relatively few numbers, and a much less-detailed enquiry; the data from it were of lower quality than those from the main study.
These data were combined with mortality data from the Confidential Enquiry into Maternal and Child Health (CEMACH), 14 formerly known as the Confidential Enquiry into Stillbirths and Deaths in Infancy (CESDI), to identify infants born at 22-32 weeks' gestation who died before admission to neonatal care and also the neonatal mortality (28 days) of infants discharged from neonatal care.
Hospital-based data (Hospital Episode Statistics (HES) linked with mortality data from the Office of National Statistics), national enquiries (Confidential Enquiries into Maternal Mortality) and surveys (UK Obstetric Surveillance System; UKOSS) of aortic dissection in pregnancy from 2003 to 2011 in England.
The information provided by these directories is obtained through publicly-available data from the Directory Enquiry database, the Electoral Register and the Database of Company Directors.
A total of 135 women who died (cases) between 2009 and 2012 from eclampsia, pulmonary embolism, severe sepsis, amniotic fluid embolism, and peripartum haemorrhage, using data from the Confidential Enquiry into Maternal Death, and another 1661 women who survived severe complications (controls) caused by these conditions (2005 2013), using data from the UK Obstetric Surveillance System.
To compare estimates of incidence of aortic dissection from hospital data linked to mortality statistics with data from the Confidential Enquiries into Maternal Mortality and UKOSS in order to test the feasibility of use of 'big data'.
We conducted the first detailed analysis of England's national hospital-level data linked to mortality statistics in order to characterise incidence and outcome of aortic dissection in pregnancy and to compare with data from the Confidential Enquiries into Maternal Mortality and UKOSS.
The effect of also including data from these units on outcomes remains a topic for future enquiry.
The data from Hertta and Corine databases was supplemented with 15 personal enquiries and interviews, including one person from each ELY Centre, during the process.
Analysis of aggregate data from routine statistical systems compiled by the EURO-PERISTAT project and comparison with data from national enquiries.
