Prediction and prevention of preterm birth: Quality assessment and systematic review of clinical practice guidelines using the AGREE II framework.

BACKGROUND: Prediction of pregnancies at risk of preterm birth (PTB) may allow targeted prevention strategies. OBJECTIVES: To assess quality of clinical practice guidelines (CPGs) and identify areas of agreement and contention in prediction and prevention of spontaneous PTB. SEARCH STRATEGY: We searched for CPGs regarding PTB prediction and prevention in asymptomatic singleton pregnancies without language restriction in January 2024. SELECTION CRITERIA: CPGs included were published between July 2017 and December 2023 and contained statements intended to direct clinical practice. DATA COLLECTION AND ANALYSIS: CPG quality was assessed using the AGREE-II tool. Recommendations were extracted and grouped under domains of prediction and prevention, in general populations and high-risk groups. MAIN RESULTS: We included 37 CPGs from 20 organizations; all were of moderate or high quality overall. There was consensus in prediction of PTB by identification of risk factors and cervical length screening in high-risk pregnancies and prevention of PTB by universal screening and treatment for asymptomatic bacteriuria, screening and treatment for BV in high-risk pregnancies, and use of preventative progesterone and cerclage. Areas of contention or limited consensus were the role of PTB clinics, universal cervical length measurement, biomarkers and cervical pessaries. CONCLUSIONS: This review identified strengths and limitations of current PTB CPGs, and areas for future research.

First-trimester prediction of preterm prelabour rupture of membranes incorporating cervical length measurement.

OBJECTIVES: To examine early pregnancy risk factors for preterm prelabour rupture of membranes (PPROM) and develop a predictive model. STUDY DESIGN: Retrospective analysis of a cohort of mixed-risk singleton pregnancies screened in the first and second trimesters in three Danish tertiary fetal medicine centres, including a cervical length measurement at 11-14 weeks, at 19-21 weeks and at 23-24 weeks of gestation. Univariable and multivariable logistic regression analyses were employed to identify predictive maternal characteristics, biochemical and sonographic factors. Receiver operating characteristic (ROC) curve analysis was used to determine predictors for the most accurate model. RESULTS: Of 3477 screened women, 77 (2.2%) had PPROM. Maternal factors predictive of PPROM in univariable analysis were nulliparity (OR 2.0 (95% CI 1.2-3.3)), PAPP-A < 0.5 MoM (OR 2.6 (1.1-6.2)), previous preterm birth (OR 4.2 (1.9-8.9)), previous cervical conization (OR 3.6 (2.0-6.4)) and cervical length ≤ 25 mm on transvaginal imaging (first-trimester OR 15.9 (4.3-59.3)). These factors all remained statistically significant in a multivariable adjusted model with an AUC of 0.72 in the most discriminatory first-trimester model. The detection rate using this model would be approximately 30% at a false-positive rate of 10%. Potential predictors such as bleeding in early pregnancy and pre-existing diabetes mellitus affected very few cases and could not be formally assessed. CONCLUSIONS: Several maternal characteristics, placental biochemical and sonographic features are predictive of PPROM with moderate discrimination. Larger numbers are required to validate this algorithm and additional biomarkers, not currently used for first-trimester screening, may improve model performance.

Attributable factors for the rising cesarean delivery rate over 3 decades: an observational cohort study.

BACKGROUND: Cesarean delivery rates continue to rise globally, the reasons for which are incompletely understood. OBJECTIVE: We aimed to characterize the attributable factors for the increasing cesarean delivery rates over a 30-year period within our health network. STUDY DESIGN: This was a planned observational cohort study across 2 hospitals (a large tertiary referral hospital and a metropolitan hospital) in Sydney, Australia using data from a previously published study. The following 2 time periods were compared: 1989-99 and 2009-16, between which the cesarean delivery rate increased from 19% to 30%. The participants were all women who had a cesarean delivery after 24 weeks' gestational age. The data were analyzed using multiple imputation and robust Poisson regression to calculate the differences in the adjusted and unadjusted relative risk of cesarean delivery and estimate the changes in the cesarean delivery rate attributable to maternal and clinical factors. The primary outcome was cesarean delivery. RESULTS: After 576 exclusions, 102,589 births were included in the analysis. Fifty-six percent of the increase in the rate of cesarean delivery was attributed to changes in the distribution of the maternal age, body mass index, and parity and to a history of previous cesarean delivery. An additional 10% of the increase was attributed to changes in the obstetrical management of the following high-risk pregnancies: multiple gestation, malpresentation (mainly breech), and preterm singleton birth. When prelabor cesarean deliveries for maternal choice, suspected fetal compromise, previous pregnancy issues, and suspected large fetus were excluded, 78% of the increase was attributed to either maternal factors or changes in the obstetrical management of these high-risk pregnancies. CONCLUSION: Most of the steep rise in the cesarean delivery rate from 19% to 30% was attributed to changes in the maternal demographic and clinical factors. This observation is relevant to developing preventative strategies that account for nulliparity, age, body mass index, and management of high-risk pregnancies.

Transverse position. Using rotation to aid normal birth-OUTcomes following manual rotation (the TURN-OUT trial): a randomized controlled trial.

BACKGROUND: The fetal occiput transverse position in the second stage of labor is associated with adverse maternal and perinatal outcomes. Prophylactic manual rotation in the second stage of labor is considered a safe and easy to perform procedure that has been used to prevent operative deliveries. OBJECTIVE: This study aimed to determine the efficacy of prophylactic manual rotation in the management of the occiput transverse position for preventing operative delivery. We hypothesized that among women who are at ≥37 weeks' gestation with a baby in the occiput transverse position early in the second stage of labor, manual rotation compared with a "sham" rotation will reduce the rate of operative delivery. STUDY DESIGN: A double-blinded, parallel, superiority, multicenter, randomized controlled clinical trial in 3 tertiary hospitals was conducted in Australia. The primary outcome was operative (cesarean, forceps, or vacuum) delivery. Secondary outcomes were cesarean delivery, serious maternal morbidity and mortality, and serious perinatal morbidity and mortality. Outcomes were analyzed by intention to treat. Proportions were compared using χ2 tests adjusted for stratification variables using the Mantel-Haenszel method or Fisher exact test. Planned subgroup analyses by operator experience and technique of manual rotation (digital or whole hand rotation) were performed. The planned sample size was 416 participants (trial registration: ACTRN12613000005752). RESULTS: Here, 160 women with a term pregnancy and a baby in the occiput transverse position in the second stage of labor, confirmed by ultrasound, were randomly assigned to receive either a prophylactic manual rotation (n=80) or a sham procedure (n=80), which was less than our original intended sample size. Operative delivery occurred in 41 of 80 women (51%) assigned to prophylactic manual rotation and 40 of 80 women (50%) assigned to a sham rotation (common risk difference, -4.2% [favors sham rotation]; 95% confidence interval, -21 to 13; P=.63). Among more experienced proceduralists, operative delivery occurred in 24 of 47 women (51%) assigned to manual rotation and 29 of 46 women (63%) assigned to a sham rotation (common risk difference, 11%; 95% confidence interval, -11 to 33; P=.33). Cesarean delivery occurred in 6 of 80 women (7.5%) in the manual rotation group and 7 of 80 women (8.7%) in the sham group. Instrumental (forceps or vacuum) delivery occurred in 35 of 80 women (44%) in the manual rotation group and 33 of 80 women (41%) in the sham group. There was no significant difference in the combined maternal and perinatal outcomes. The trial was terminated early because of limited resources. CONCLUSION: Planned prophylactic manual rotation did not result in fewer operative deliveries. More research is needed in the use of manual rotation from the occiput transverse position for preventing operative deliveries.

Persistent occiput posterior position outcomes following manual rotation: a randomized controlled trial.

BACKGROUND: Persistent occiput posterior position in labor is associated with adverse maternal and perinatal outcomes. Prophylactic manual rotation from the occiput posterior position to the occiput anterior position in the second stage of labor is considered a safe and easy to perform procedure that in observational studies has shown promise as a method for preventing operative deliveries. OBJECTIVE: This study aimed to determine the efficacy of prophylactic manual rotation in the management of occiput posterior position for preventing operative delivery. The hypothesis was that among women who are at least 37 weeks pregnant and whose baby is in the occiput posterior position early in the second stage of labor, manual rotation will reduce the rate of operative delivery compared with the "sham" rotation. STUDY DESIGN: A double-blinded, parallel, superiority, multicenter, randomized controlled clinical trial in 4 tertiary hospitals was conducted in Australia. A total of 254 nulliparous and parous women with a term pregnancy and a baby in the occiput posterior position in the second stage of labor were randomly assigned to receive either a prophylactic manual rotation (n=127) or a sham rotation (n=127). The primary outcome was operative delivery (cesarean, forceps, or vacuum delivery). Secondary outcomes were cesarean delivery, combined maternal mortality and serious morbidity, and combined perinatal mortality and serious morbidity. Analysis was by intention to treat. Proportions were compared using chi-square tests adjusted for stratification variables using the Mantel-Haenszel method or the Fisher exact test. Planned subgroup analyses by operator experience and by manual rotation technique (digital or whole-hand rotation) were performed. RESULTS: Operative delivery occurred in 79 of 127 women (62%) assigned to prophylactic manual rotation and 90 of 127 women (71%) assigned to sham rotation (common risk difference, 12; 95% confidence interval, -1.7 to 26; P=.09). Among more experienced operators or investigators, operative delivery occurred in 46 of 74 women (62%) assigned to manual rotation and 52 of 71 women (73%) assigned to a sham rotation (common risk difference, 18; 95% confidence interval, -0.5 to 36; P=.07). Cesarean delivery occurred in 22 of 127 women (17%) in both groups. Instrumental delivery (forceps or vacuum) occurred in 57 of 127 women (45%) assigned to prophylactic manual rotation and 68 of 127 women (54%) assigned to sham rotation (common risk difference, 10; 95% confidence interval, -3.1 to 22; P=.14). There was no significant difference in the combined maternal and perinatal outcomes. CONCLUSION: Prophylactic manual rotation did not result in a reduction in the rate of operative delivery. Given manual rotation was associated with a nonsignificant reduction in operative delivery, more randomized trials are needed, as our trial might have been underpowered. In addition, further research is required to further explore the potential impact of operator or investigator experience.

First Trimester Protein Biomarkers for Risk of Spontaneous Preterm Birth: Identifying a Critical Need for More Rigorous Approaches to Biomarker Identification and Validation.

BACKGROUND: Spontaneous preterm birth is the leading cause of perinatal morbidity and mortality worldwide and continues to present a major clinical dilemma. We previously reported that a number of protein species were dysregulated in maternal serum collected at 11-13+6 weeks' gestation from pregnancies that continued to labour spontaneously and deliver preterm. OBJECTIVES AND METHODS: In this study, we aimed to validate changes seen in 4 candidate protein species: alpha-1-antitrypsin, vitamin D-binding protein (VDBP), alpha-1beta-glycoprotein and apolipoprotein A-1 in a larger cohort of women using a western blot approach. RESULTS: Serum levels of all 4 proteins were reduced in women who laboured spontaneously and delivered preterm. This reduction was significant for VDBP (p = 0.04), which has been shown to be involved in a plethora of essential biological functions, including actin scavenging, fatty acid transport, macrophage activation and chemotaxis. CONCLUSIONS: The decrease in select proteoforms of VDBP may result in an imbalance in the optimal intrauterine environment for the developing foetus as well as to a successful uncomplicated pregnancy. Thus, certain (phosphorylated) species of VDBP may be of value in developing a targeted approach to the early prediction of spontaneous preterm labour. Importantly, this study raises the importance of a focus on proteoforms and the need for any biomarker validation process to most effectively take these into account rather than the more widespread practice of simply focussing on the primary amino acid sequence of a protein.

Influence of maternal and placental factors on newborn body composition.

AIM: The objective of this study was to assess whether maternal characteristics, placental size or histological chorioamnionitis was associated with newborn body composition. Furthermore, we sought to determine whether placental weight may mediate the association between maternal pre-pregnancy weight and age with newborn body composition. METHODS: A cross-sectional study was conducted at Royal Prince Alfred Hospital, Sydney, Australia. This study included 136 healthy, singleton, term-born newborns. Recruitment was stratified by newborn body fat percentiles (gender and gestational adjusted). Body fat was assessed by air displacement plethysmography. Placental examination was conducted by an anatomical pathologist. Maternal (chorioamnionitis) and fetal (chorionic and umbilical vasculitis, funisitis) inflammatory responses were classified according to Redline criteria. RESULTS: Maternal pre-pregnancy weight, parity, labour, placental weight and surface area were associated with newborn fat mass and fat-free mass. Gestational diabetes and maternal age were associated with newborn fat mass but not fat-free mass. There was no association between histological chorioamnionitis and newborn body composition; however, spontaneous onset of labour was strongly associated with the presence of histological chorioamnionitis. Only 25-31% of the association of maternal weight and age with newborn fat mass was mediated via the placenta. CONCLUSIONS: Maternal factors associated with newborn fat mass and fat-free mass differed, indicating that different mechanisms control fat mass and fat-free mass. Our mediation analysis suggests that placental weight partly mediates the association of maternal factors with newborn body composition. Histological chorioamnionitis was not associated with newborn body composition.

Analysis of the integrity of ultrasound probe covers used for transvaginal examinations.

BACKGROUND: Ultrasound probe covers should be used for any ultrasound procedure where there is contact with body fluids or mucous membranes. The type and quality of probe covers used in clinical practice differ widely and studies in the early 1990s showed that condoms were more superior for use with transvaginal examinations than commercial probe covers. Since then, although products have changed, there have been no further studies to assess the breakage rate of different probe covers. The objectives of this study were to assess the integrity of the most commonly used probe covers for transvaginal ultrasound examinations under clinical conditions and report the breakage rate. METHODS: The study was conducted in public and private hospitals and private practices. A total of 500 covers for each of 10 brands of commercial covers and condoms (latex and latex free) were distributed to ultrasound practitioners. The transvaginal ultrasound examination practice was unchanged except that all covers were placed in a container for assessment instead of discarding post ultrasound examination. All covers were collected and subjected to a water leak test. Covers that broke upon deployment onto the ultrasound probe prior to the ultrasound examination were recorded. All covers that were broken or had microtears or leaks were recorded as well as photographed. Statistical analysis was performed along with Chi-squared analysis of the data and significance considered at P < 0.05. RESULTS: None of the commercial covers broke upon deployment onto the ultrasound probe prior to ultrasound examination. A total of 5000 probe covers were examined post-transvaginal ultrasound examinations. The breakage rate for condoms ranged from 0.4% to 13% and for commercial covers 0-5%. Statistical analysis of the data by comparison of p-values revealed that the best performing group were the commercial non-latex probe covers and worst performing group were the non-latex condoms. CONCLUSION: The breakage rates for commercial covers were not as high as previously reported and do not break upon deployment onto the ultrasound probe. This is the first comprehensive study that thoroughly evaluated the integrity of commercial covers and condoms used for transvaginal ultrasound examination in a clinical setting, with regards to brand, numbers and types of covers assessed.

A Novel Early Pregnancy Risk Prediction Model for Gestational Diabetes Mellitus.

INTRODUCTION: Accurate early risk prediction for gestational diabetes mellitus (GDM) would target intervention and prevention in women at the highest risk. We evaluated novel biomarker predictors to develop a first-trimester risk prediction model in a large multiethnic cohort. METHODS: Maternal clinical, aneuploidy and pre-eclampsia screening markers (PAPP-A, free hCGß, mean arterial pressure, uterine artery pulsatility index) were measured prospectively at 11-13+6 weeks' gestation in 980 women (248 with GDM; 732 controls). Nonfasting glucose, lipids, adiponectin, leptin, lipocalin-2, and plasminogen activator inhibitor-2 were measured on banked serum. The relationship between marker multiples-of-the-median and GDM was examined with multivariate regression. Model predictive performance for early (< 24 weeks' gestation) and overall GDM diagnosis was evaluated by receiver operating characteristic curves. RESULTS: Glucose, triglycerides, leptin, and lipocalin-2 were higher, while adiponectin was lower, in GDM (p < 0.05). Lipocalin-2 performed best in Caucasians, and triglycerides in South Asians with GDM. Family history of diabetes, previous GDM, South/East Asian ethnicity, parity, BMI, PAPP-A, triglycerides, and lipocalin-2 were significant independent GDM predictors (all p < 0.01), achieving an area under the curve of 0.91 (95% confidence interval [CI] 0.89-0.94) overall, and 0.93 (95% CI 0.89-0.96) for early GDM, in a combined multivariate prediction model. CONCLUSIONS: A first-trimester risk prediction model, which incorporates novel maternal lipid markers, accurately identifies women at high risk of GDM, including early GDM.

Providing quality care for women with vasa praevia: Challenges and barriers faced by Australian midwives.

OBJECTIVE: To explore the barriers to providing quality maternity care for women with vasa praevia as identified by Australian midwives. DESIGN: A qualitative descriptive study using semi-structured in-depth telephone interviews. SETTING: Australian maternity system. METHODS: Midwives were recruited from across Australia. Interviews were audio-recorded, transcribed verbatim, and analysed using thematic analysis. PARTICIPANTS: Twenty midwives from five Australian states practising in 15 different public or private hospitals who had cared for at least one woman with vasa praevia during 2010-2016 were interviewed. More than half of the participants held senior positions. Twelve were involved in a neonatal death or 'near-miss' due to vasa praevia. FINDINGS: Two categories and five themes were identified in relation to barriers to the provision of quality care. Practitioner-level barriers included two themes: identifying lack of midwifery education and lack of knowledge. System-level barriers included lack of a local policy to guide practice, limited information for women, and paucity of research about vasa praevia. CONCLUSION: Midwives experienced a number of barriers in caring for women with vasa praevia. Offering more comprehensive pre-registration and continuing professional education to midwives, developing local protocols, and providing clear written information for women may improve the provision of quality care. IMPLICATIONS FOR PRACTICE: Midwives have a critical role in caring for and supporting women with vasa praevia. Improving midwives' knowledge with contemporary evidence and clinical guidelines could enable them to deliver safer maternity care and improve a women's journey through this potentially catastrophic condition.

The experience of vasa praevia for Australian midwives: A qualitative study.

BACKGROUND: Vasa praevia can cause stillbirth or early neonatal death if it is not diagnosed antenatally and managed appropriately. Experiencing undiagnosed vasa praevia during labour is challenging and traumatic for women and their care providers. Little is known about the experiences of midwives who care for these women. AIM: To investigate the experience of Australian midwives caring for women with undiagnosed vasa praevia during labour and birth. METHODS: A qualitative descriptive study was conducted with midwives in Australia who had cared for at least one woman with vasa praevia during 2010-2016. Semi-structured in-depth telephone interviews were conducted and analysed using thematic analysis. FINDINGS: Twelve of the 20 midwives interviewed were involved in a neonatal death and/or near-miss due to vasa praevia. There was one over-arching theme, which described the 'devastating and dreadful experience' for the midwives. This had two inter-related categories of feeling the personal impacts and addressing the professional processes. Feeling scared, shocked, and guilty described how the experience took its toll on the midwives personally. The professional processes included working in organised chaos; feeling for the parents; finding communication to be hard; and, doing their best to save the baby. DISCUSSION: Caring for women who experienced ruptured vasa praevia had a profound impact on the emotional and professional well-being of midwives even when the baby survived. CONCLUSION: Ruptured vasa praevia was recognised as a traumatic experience that warrants serious considerations from maternity care providers, managers and policy makers. Midwives should be supported and adequately prepared to cope with traumatic events.

Proteomic analysis of first trimester maternal serum to identify candidate biomarkers potentially predictive of spontaneous preterm birth.

Spontaneous preterm birth (sPTB) remains a major clinical dilemma; current diagnostics and interventions have not reduced the rate of this serious healthcare burden. This study characterizes differential protein profiles and post-translational modifications (PTMs) in first trimester maternal serum using a refined top-down approach coupling two-dimensional gel electrophoresis (2DE) and mass spectrometry (MS) to directly compare subsequent term and preterm labour events and identify marked protein differences. 30 proteoforms were found to be significantly increased or decreased in the sPTB group including 9 phosphoproteins and 11 glycoproteins. Changes occurred in proteins associated with immune and defence responses. We identified protein species that are associated with several clinically relevant biological processes, including interrelated biological networks linked to regulation of the complement cascade and coagulation pathways, immune modulation, metabolic processes and cell signalling. The finding of altered proteoforms in maternal serum from pregnancies that delivered preterm suggests these as potential early biomarkers of sPTB and also possible mediators of the disorder. BIOLOGICAL SIGNIFICANCE: Identifying changes in protein profiles is critical in the study of cell biology, and disease treatment and prevention. Identifying consistent changes in the maternal serum proteome during early pregnancy, including specific protein PTMs (e.g. phosphorylation, glycosylation), is likely to provide better opportunities for prediction, intervention and prevention of preterm birth. This is the first study to examine first trimester maternal serum using a highly refined top-down proteomic analytical approach based on high resolution 2DE coupled with mass spectrometry to directly compare preterm (<37 weeks) and preterm (≥37 weeks) events and identify select protein differences between these conditions. As such, the data present a promising avenue for translation of biomarker discovery to a clinical setting as well as for future investigation of underlying aetiological processes.

Is ultrasound measured fetal biometry predictive of intrapartum caesarean section for failure to progress?

BACKGROUND: There are global concerns regarding excessive caesarean rates, which could be reduced by identification of risk factors leading to preventative measures such as induction of labour. AIMS: This study aims to describe the association between antenatal ultrasound and emergency caesarean section for: (i) failure to progress; (ii) other indications; and (iii) any indication. MATERIALS AND METHODS: Women who had an ultrasound in pregnancy between 36(+0/7) to 38(+6/7) weeks at Royal Prince Alfred Hospital from January 2005 to June 2009 were included. Ultrasound parameters were linked to clinical parameters from the maternity database. Missing clinical data were imputed and multiple logistic regression performed. RESULTS: Fetal biometry data were available for 2006 pregnancies. After adjusting for maternal age, height, body mass index, parity, previous caesarean section and diabetes, caesarean section for failure to progress was associated with estimated fetal weight (odds ratio (OR) 2.24 (95% CI: 1.76-2.84) per 500 g increase); or biparietal diameter (OR 1.51 (1.16-1.97) per 5 mm increase) and abdominal circumference (OR for the 4th quartile (>75th centile) compared with the 10-25th centile group was 2.09 (1.13-3.85)).* There were also non-linear associations between components of fetal biometry and caesarean section for fetal distress and for any indication. CONCLUSIONS: Components of fetal biometry in the third trimester are associated with intrapartum caesarean section for failure to progress. These parameters could be incorporated into models to predict emergency caesarean section which could lead to implementation of preventative strategies. *[Corrections added on 29 January 2018, after first online publication, '(OR for the 4th quartile (>7th centile)' has been changed to '(OR for the 4th quartile (>75th centile)'.].

A first trimester prediction model for gestational diabetes utilizing aneuploidy and pre-eclampsia screening markers.

OBJECTIVE: We examined whether first trimester aneuploidy and pre-eclampsia screening markers predict gestational diabetes mellitus (GDM) in a large multi-ethnic cohort and the influence of local population characteristics on markers. METHODS: Clinical and first trimester markers (mean arterial pressure (MAP), uterine artery pulsatility index (UtA PI), pregnancy associated plasma protein A (PAPP-A), free-ß human chorionic gonadotropin (free-hCGß)) were measured in a case-control study of 980 women (248 with GDM, 732 controls) at 11 to 13 + 6 weeks' gestation. Clinical parameters, MAP-, UtA PI-, PAPP-A-, and free-hCGß-multiples-of-the-median (MoM) were compared between GDM and controls; stratified by ethnicity, parity, and GDM diagnosis <24 versus ≥24 weeks' gestation. GDM model screening performance was evaluated using AUROC. RESULTS: PAPP-A- and UtA PI-MoM were significantly lower in GDM versus controls (median ((IQR) PAPP-A-MoM 0.81 (0.58-1.20) versus 1.00 (0.70-1.46); UtA PI-MoM 1.01 (0.82-1.21) versus 1.05 (0.84-1.29); p < .05). Previous GDM, family history of diabetes, south/east Asian ethnicity, parity, BMI, MAP, UtA PI, and PAPP-A were significant predictors in multivariate analysis (p < .05). The AUC for a model based on clinical parameters was 0.88 (95%CI 0.85-0.92), increasing to 0.90 (95%CI 0.87-0.92) with first trimester markers combined. The combined model best predicted GDM <24 weeks' gestation (AUC 0.96 (95%CI 0.94-0.98)). CONCLUSIONS: Addition of aneuploidy and pre-eclampsia markers is cost-effective and enhances early GDM detection, accurately identifying early GDM, a high-risk cohort requiring early detection, and intervention. Ethnicity and parity modified marker association with GDM, suggesting differences in pathophysiology and vascular risk.

Epidemic of large babies highlighted by use of INTERGROWTH21st international standard.

OBJECTIVE: To compare birth weights in central Sydney to the INTERGROWTH21st international standard to describe current trends in relation to optimal growth and to define areas that may benefit from improved obstetric surveillance and intervention. METHODS: Retrospective analysis of prospectively collected cohort. DESIGN: hospital-based cohort study. SETTING: Sydney Local Health District, Australia. POPULATION OR SAMPLE: women with singleton pregnancies who had first trimester screening for aneuploidy between 16 April, 2010 and 9 March, 2012. Analysis of 2966 births. MAIN OUTCOME MEASURES: Large for gestational age (LGA) >4000 g, >4500 g, >5000 g, >90th, >95th, >97th centiles and small for gestational age (SGA) <1500 g, <2500 g,

A New Approach to Developing Birth Weight Reference Charts: A Retrospective Observational Study.

INTRODUCTION: Birth weight reference charts based on historical infant birth weights have significant bias at preterm gestations because many preterm births are associated with abnormal growth. This study aims to determine whether more accurate birth weight charts can be constructed using data only from births that follow spontaneous onset of labour. MATERIALS AND METHODS: This study was a single-centre retrospective observational study of 115,712 singleton live births. Births were classified as spontaneous or iatrogenic. Quantile regression was used to model the relationship between gestational age, sex, labour onset, and birth weight. Comparison was made of birth weights in the spontaneous and iatrogenic cohorts by gestation, and to existing ultrasound-based charts. RESULTS: Birth weights of spontaneous and iatrogenic births were significantly different for gestational age at the median and 10th centiles. Iatrogenic preterm infants weighed less than their spontaneous preterm counterparts. Median and 10th centile birth weights derived from the spontaneous birth cohort closely approximate previous ultrasound-based curves. DISCUSSION: Iatrogenic births are more likely to be associated with pre-existing growth disturbance. Inclusion of these data has significant impact on centile charts. Birth weight charts derived from only spontaneous births may offer a more accurate reference for clinicians.