Maternal pre-pregnancy body mass index and risk of preterm birth: a collaboration using large routine health datasets

BACKGROUND

Preterm birth (PTB) is a leading cause of child morbidity and mortality. Evidence suggests an increased risk with both maternal underweight and obesity, with some studies suggesting underweight might be a greater factor in spontaneous PTB (SPTB) and that the relationship might vary by parity. Previous studies have largely explored established body mass index (BMI) categories. Our aim was to compare associations of maternal pre-pregnancy BMI with any PTB, SPTB and medically indicated PTB (MPTB) among nulliparous and parous women across populations with differing characteristics, and to identify the optimal BMI with lowest risk for these outcomes.

METHODS

We used three UK datasets, two USA datasets and one each from South Australia, Norway and Denmark, together including just under 29 million pregnancies resulting in a live birth or stillbirth after 24 completed weeks gestation. Fractional polynomial multivariable logistic regression was used to examine the relationship of maternal BMI with any PTB, SPTB and MPTB, among nulliparous and parous women separately. The results were combined using a random effects meta-analysis. The estimated BMI at which risk was lowest was calculated via differentiation and a 95% confidence interval (CI) obtained using bootstrapping.

RESULTS

We found non-linear associations between BMI and all three outcomes, across all datasets. The adjusted risk of any PTB and MPTB was elevated at both low and high BMIs, whereas the risk of SPTB was increased at lower levels of BMI but remained low or increased only slightly with higher BMI. In the meta-analysed data, the lowest risk of any PTB was at a BMI of 22.5 kg/m2 (95% CI 21.5, 23.5) among nulliparous women and 25.9 kg/m2 (95% CI 24.1, 31.7) among multiparous women, with values of 20.4 kg/m2 (20.0, 21.1) and 22.2 kg/m2 (21.1, 24.3), respectively, for MPTB; for SPTB, the risk remained roughly largely constant above a BMI of around 25-30 kg/m2 regardless of parity.

CONCLUSIONS

Consistency of findings across different populations, despite differences between them in terms of the time period covered, the BMI distribution, missing data and control for key confounders, suggests that severe under- and overweight may play a role in PTB risk.

Experiences of medical traumatic stress in parents of children with medical complexity

BACKGROUND AND OBJECTIVES

Parents of children with medical complexity (CMC) experience high levels of stress and adverse mental health outcomes. Pediatric medical traumatic stress (PMTS) could be an important contributor that has not yet been explored. PMTS describes parents' reactions to their child's illness and medical treatment and can lead to post-traumatic stress symptoms. This is the first study to describe the experiences and impact of PMTS among parents of CMC.

METHODS

We conducted semi-structured interviews with 22 parents of CMC. Reflexive thematic analysis was used to generate themes that described the experiences of PMTS and potential contributing factors in the healthcare setting. Themes were validated by study participants.

RESULTS

Parents experienced a spectrum of events and circumstances that impacted PMTS. These corresponded to three major themes: (a) the distinctive context of being the parent of a CMC, (b) interactions with healthcare providers that can hurt or heal and (c) system factors that set the stage for trauma. The consequences of repeated PMTS were a common point of emphasis among all the themes. Parents identified numerous changes that could mitigate PMTS such as acknowledgement of trauma and provision of proactive mental health support.

CONCLUSIONS

Our study highlights the issue of PMTS among parents of CMC and presents opportunities to mitigate their traumatic experiences. Supporting the integration of trauma-informed care practices, increasing awareness of PMTS and advocating for parental mental health services could better support parents and families.

Evaluation of an intervention to reduce tidal volumes in ventilated ICU patients

BACKGROUND

There is considerable evidence that the use of tidal volumes <6 ml kg(-1) predicted body weight (PBW) reduces mortality in mechanically ventilated patients. We evaluated the effectiveness of using a large screen displaying delivered tidal volume in ml kg(-1) (PBW) for reducing tidal volumes.

METHODS

We assessed the intervention in two 6-month periods. A qualitative study was undertaken after the intervention period to examine staff interaction with the intervention. The study was conducted in a mixed medical and surgical intensive care unit at University Hospitals Bristol, UK. Consecutive patients requiring controlled mechanical ventilation for more than 1 h were included. Alerts were triggered when tidal volume breached predetermined targets and these alerts were visible to ICU clinicians in real time.

RESULTS

A total of 199 patients with 7640 h of data were observed during the control time period and 249 patients with 10 656 h of data were observed in the intervention period. Time spent with tidal volumes <6 ml kg(-1) PBW increased from 17.5 to 28.6% of the period of controlled mechanical ventilation. Time spent with a tidal volume <8 ml kg(-1) PBW increased from 60.6 to 73.9%. The screens were acceptable to staff and stimulated an increase in attendance of clinicians at the bedside to adjust ventilators.

CONCLUSIONS

Changing the format of data and displaying it with real-time alerts reduced delivered tidal volumes. Configuring information in a format more likely to result in desired outcomes has the potential to improve the translation of evidence into practice.

Systematic review and meta-analysis of the effect of intraoperative α₂-adrenergic agonists on postoperative behaviour in children

Undergoing general anaesthesia is distressing for children, with up to two-thirds demonstrating abnormal behaviours after their procedure, such as emergence delirium (ED) and post-hospitalization behaviour change. The aim of this systematic review was to determine the effect of intraoperative i.v. α₂-adrenergic agonists on postoperative behaviour in children. We included published full-text reports of randomized controlled trials involving children who received i.v. clonidine or dexmedetomidine after induction of general anaesthesia, who were assessed for postoperative behavioural disturbance. After screening of references identified by the search strategy, a data collection form was developed and piloted. Data extraction was performed by one reviewer and checked by a second. Twelve randomized trials met the inclusion criteria. Ten studies (n=669) reported dichotomous data that were included in the pooled analysis of α₂-adrenergic agonists vs placebo. There was strong evidence that i.v. α₂-adrenergic agonists reduced postoperative ED (overall summary odds ratio 0.28, 95% confidence interval 0.19-0.40, P<0.001). No studies examined post-hospitalization negative behaviour changes. There was evidence that α₂-adrenergic agonists prolonged time in the recovery room. No adverse haemodynamic events were reported in any arm of any study. This meta-analysis provides evidence that intraoperative i.v. α₂-adrenergic agonists reduce the incidence of emergency delirium in children. The prolongation of time in recovery is unlikely to be clinically relevant. The absence of data regarding the effect on post-hospitalization behavioural changes provides an opportunity for future research.

Magnetic resonance guided general surgery

Image guided surgery can be defined as the intraoperative use of a radiologicai technique to give the surgeon information not available from direct inspection or palpation of the surgical field. This information may then be used to change the course of an operative procedure. Magnetic resonance (MR) imaging has the potential to be the most useful radiologicai technique in the developing field of image guided surgery.

Variations in T1 and T2 relaxation times of normal appearing white matter and lesions in multiple sclerosis

OBJECTIVE

To investigate the variation in T1 and T2 relaxation times of normal appearing white matter (NAWM) and lesions in multiple sclerosis (MS) throughout the brain.

BACKGROUND

The magnetic resonance imaging (MRI) sequence fast FLAIR (fluid attenuated inversion recovery) has demonstrated overall increased lesion detection when compared to conventional or fast spin echo (FSE) but fewer lesions in the posterior fossa and spinal cord. The reasons for this are unknown, but may be due to variations in the T1 and T2 relaxation times within NAWM and MS lesions.

METHOD

Ten patients and 10 controls underwent MRI of the brain which involved FSE, fast FLAIR and the measurement of T1 and T2 relaxation times.

RESULTS

Of 151 lesions analysed (22 infra-tentorial, 129 supra-tentorial), eight were missed by the fast FLAIR sequence. T1 and T2 relaxation times in normal controls were longer in the infra-tentorial, than supra-tentorial, region. Patient NAWM relaxation times were prolonged compared with control values in both regions. Lesions demonstrated longer relaxation times than either control white matter or patient NAWM in both regions, however this difference was less marked infra-tentorially. The eight posterior fossa lesions not visible on the fast FLAIR sequence were characterised by short T1 and T2 relaxation times which overlapped with the patient NAWM for both T1 and T2 and with control values for T2 relaxation times.

CONCLUSION

Both lesion and NAWM relaxation time characteristics vary throughout the brain. The T1 and T2 relaxation times of infra-tentorial lesions are closer to the relaxation times of local NAWM than supra-tentorial lesions, resulting in reduced contrast between posterior fossa lesions and the background NAWM. Consequently the characteristics of some lesions overlap with those of NAWM resulting in reduced conspicuity. By utilising this information, it may be possible to optimise fast FLAIR sequences to improve infra-tentorial lesion detection.

Upright dynamic MR defaecating proctography in an open configuration MR system

We describe our experience evaluating an MR proctography technique using an open 0.5 T MR system. Evacuation of a gadolinium-containing rectal contrast agent was dynamically imaged in the upright position using a fast gradient echo sequence. Anatomical and functional abnormalities were documented. Results from 40 patients who underwent this technique are reported. The method is proposed as an alternative to conventional fluoroscopic proctography.