Title: Estimating the risk of adverse birth outcomes in pregnant women undergoing non-obstetric surgery using routinely collected NHS data
Funder: Department of Health (England)

Abstract: The research question has arisen from questions posed by patients in a high risk obstetric anaesthetic clinic. Women undergo non-obstetric surgery in approximately 1-2% of pregnancies. Common operations include appendicectomy cancer surgery and orthopaedic procedures. Previous studies have suggested an associated increased risk in prematurity or perinatal death. However they are problematic for a number of reasons. Firstly most studies are relatively old (20-40 years old) and are unlikely to be representative of current outcomes given advances in anaesthesia surgical technique and neonatal care. Secondly they are generally poorly controlled for confounders. Furthermore there have been few attempts to quantify risk by type of surgery. A relatively recent review of the literature pointed out a critical need for better data with careful attention to confounders. The aim of our proposal is to quantify the risk of adverse birth outcomes in pregnant women undergoing non-obstetric surgery. We plan to utilise a large national administrative database of English hospital admissions held within our unit in the School of Public Health at Imperial College London. This holds data on some 4 million births over 10 years from 2002/3 to 2012/13. Our preliminary unadjusted analysis on one year of data suggests we should be able to identify around 85000 procedures occurring during pregnancy over a one-year period. In this piloted unadjusted analysis of one year we were able to identify a statistically significantly increased risk of pre-term delivery of 1.54 compared with women who had not had a procedure during pregnancy. Increasing our sample size by a factor of 10 will allow us to drill down into the effects of broad groups of procedures in different trimesters and outcomes. As well as information about the mother’s age co-morbidities and socio-economic status we will also be able to utilise fields attached to the mother’s record providing information about the infant such as birth weight gestational age and outcomes such as in-hospital mortality. Because of the volume of data we will also be able to look at some broad subsets of patients and procedures as well as potentially the trimester in which the procedure occurred. Outcomes we intend to explore include still birth miscarriage pre-term delivery fetal death in hospital low birth weight and prolonged length of stay for the infant.We will carry out a descriptive analysis of the data describing counts of events by year maternal age procedure type etc. We will examine subsets of data with well coded fields for multiple gestations parity gestational age and birth weight by selecting data from trusts with greater completeness of data items We will then calculate the relative odds of an adverse birth outcome occurring in women who have had a non-obstetric surgical procedure compared with women who haven’t adjusting for confounders using logistic regression (adjusting for the clustering of patients within hospitals if necessary). We will write up our findings to be published in the academic peer reviewed press and formulate guidelines for information for both patients and clinicians.BenefitsNon-obstetric surgery during pregnancy is a relatively uncommon event and most doctors will not have regular exposure to these patients. Our aim is therefore to raise awareness of the issue and to provide evidence that can be easily located when required. We hope to raise awareness of this issue and publish this evidence so that it can be easily located when required. A combination of peer-reviewed publication presentation at surgical anaesthetic and general practice conferences and guidelines or recommendations published by national bodies will fulfil these requirements.In addition it will be important to provide a patient information summary online. This is a highly motivated patient group who will tend to seek up-to-date information and may even be more informed than their medical team. Our data will specify the risk of an adverse birth outcome within the NHS over the past 10 years derived from patients in very similar circumstances to themselves. It will therefore be of particular interest and benefit to them.


Research activity codes: 7.3 MANAGEMENT AND DECISION MAKING
Health categories: REPRODUCTIVE HEALTH AND CHILDBIRTH