Obstetrics and Gynaecology - Research Publications
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ItemRisk of obstetric anal sphincter injury among women who birth vaginally after a prior caesarean section: A state-wide cohort study(WILEY, 2022-07)OBJECTIVE: Vaginal birth after caesarean (VBAC) has been suggested to be associated with an increased risk of obstetric anal sphincter injury (compared with primiparous women who birth vaginally). However, prior studies have been small or have used outdated methodology. We set out to validate whether the risk of obstetric anal sphincter injury among women having their first VBAC is greater than that among primiparous women having a vaginal birth. DESIGN: State-wide retrospective cohort study. SETTING: Victoria, Australia. POPULATION: All births (455 000) between 2009 and 2014. METHODS: The risk of severe perineal injury between the first vaginal birth and the first VBAC was compared, after adjustment for potential confounding variables. Covariates were examined using logistic regression for categorical data and the Wilcoxon rank-sum test for continuous data. Missing data were handled using multiple imputation; the analysis was performed using regression adjustment and stata 16 multiple imputation and suite of effects commands. RESULTS: Women having a VBAC (n = 5429) were significantly more likely than primiparous women (n = 123 353) to sustain a third- or fourth-degree tear during vaginal birth (7.1 versus 5.7%, p < 0.001). After adjustment for mode of birth, body mass index, maternal age, infant birthweight, episiotomy and epidural, there was a 21% increased risk of severe perineal injury (RR 1.21, 95% CI 1.07-1.38). CONCLUSIONS: Women having their first VBAC have a significantly increased risk of sustaining a third- or fourth-degree tear, compared with primiparous women having a vaginal birth. Patient counselling and professional guidelines should reflect this increased risk.
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ItemNo Preview AvailableDevelopmental Outcomes for Children After Elective Birth at 39 Weeks' Gestation(AMER MEDICAL ASSOC, 2022-07)IMPORTANCE: Elective births at 39 weeks' gestation are increasing. While this option may improve maternal and perinatal outcomes compared with expectant management, longer-term childhood developmental outcomes are uncertain. OBJECTIVE: To investigate the association between elective birth at 39 weeks' gestation and the risk of childhood developmental vulnerability. DESIGN, SETTING, AND PARTICIPANTS: For this cohort study, 2 causal inference analyses were conducted using Australian statewide, population-based data. Perinatal data from births between January 1, 2005, and December 31, 2013, were linked to childhood developmental outcomes at age 4 to 6 years (assessed using multiple imputation via inverse probability-weighted regression adjustment). Data analyses were conducted between September 7 and November 9, 2021. EXPOSURES: Two exposure groups were considered: (1) elective birth between 39 weeks and 0 days' and 39 weeks and 6 days' gestation vs expectant management and (2) birth via induction of labor vs planned cesarean delivery among those born electively at 39 weeks' gestation. MAIN OUTCOMES AND MEASURES: Childhood developmental vulnerability at school entry, defined as scoring below the 10th percentile in at least 2 of 5 developmental domains (physical health and well-being, social competence, emotional maturity, school-based language and cognitive skills, and communication skills and general knowledge). RESULTS: Of 176 236 births with linked outcome data, 88 165 met the inclusion criteria. Among these, 15 927 (18.1%) were elective births at 39 weeks' gestation (induction of labor or planned cesarean delivery), and 72 238 (81.9%) were expectantly managed with subsequent birth between 40 and 43 weeks' gestation. Compared with expectant management, elective birth at 39 weeks' gestation was not associated with an altered risk of childhood global developmental vulnerability (adjusted relative risk [aRR], 1.03; 95% CI, 0.96-1.12) or with developmental vulnerability in any of the individual domains. In an analysis restricted to elective births at 39 weeks' gestation, induction of labor (n = 7928) compared with planned cesarean delivery (n = 7999) was not associated with childhood developmental vulnerability (aRR, 0.96; 95% CI, 0.82-1.12) or with vulnerability in any individual domains. CONCLUSIONS AND RELEVANCE: In this cohort study, elective birth at 39 weeks' gestation was not associated with childhood developmental vulnerability. For those born electively at 39 weeks' gestation, birth after induction of labor or by elective cesarean delivery had similar developmental outcomes.
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ItemAccelerated fetal growth velocity across the third trimester is associated with increased shoulder dystocia risk among fetuses who are not large-for-gestational-age: A prospective observational cohort study(PUBLIC LIBRARY SCIENCE, 2021-10-20)OBJECTIVE: To investigate whether fetuses with accelerated third trimester growth velocity are at increased risk of shoulder dystocia, even when they are not large-for-gestational-age (LGA; estimated fetal weight (EFW) >95th centile). METHODS: Fetal growth velocity and birth outcome data were prospectively collected from 347 nulliparous women. Each had blinded ultrasound biometry performed at 28 and 36 weeks' gestation. Change in EFW and abdominal circumference (AC) centiles between 28-36 weeks were calculated, standardised over exactly eight weeks. We examined the odds of shoulder dystocia with increasing EFW and AC growth velocities among women with 36-week EFW ≤95th centile (non-LGA), who went on to have a vaginal birth. We then examined the relative risk (RR) of shoulder dystocia in cases of accelerated EFW and AC growth velocities (>30 centiles gained). Finally, we compared the predictive performances of accelerated fetal growth velocities to 36-week EFW >95th centile for shoulder dystocia among the cohort planned for vaginal birth. RESULTS: Of the 226 participants who had EFW ≤95th centile at 36-week ultrasound and birthed vaginally, six (2.7%) had shoulder dystocia. For each one centile increase in EFW between 28-36 weeks, the odds of shoulder dystocia increased by 8% (odds ratio (OR [95% Confidence Interval (CI)]) = 1.08 [1.04-1.12], p<0.001). For each one centile increase in AC between 28-36 weeks, the odds of shoulder dystocia increased by 9% (OR[95%CI] = 1.09 [1.05-1.12], p<0.001). When compared to the rest of the cohort with normal growth velocity, accelerated EFW and AC velocities were associated with increased relative risks of shoulder dystocia (RR[95%CI] = 7.3 [1.9-20.6], p = 0.03 and 4.8 [1.7-9.4], p = 0.02 respectively). Accelerated EFW or AC velocities predicted shoulder dystocia with higher sensitivity and positive predictive value than 36-week EFW >95th centile. CONCLUSIONS: Accelerated fetal growth velocities between 28-36 weeks' gestation are associated with increased risk of shoulder dystocia, and may predict shoulder dystocia risk better than the commonly used threshold of 36-week EFW >95th centile.
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ItemCirculating Growth Differentiation Factor 15 Is Increased Preceding Preeclampsia Diagnosis: Implications as a Disease Biomarker(WILEY, 2021-08-17)Background We investigated the biomarker potential of growth differentiation factor 15 (GDF-15), a stress response protein highly expressed in placenta, to predict preeclampsia. Methods and Results In 2 prospective cohorts (cohort 1: 960 controls, 39 women who developed preeclampsia; cohort 2: 950 controls, 41 developed preeclampsia), plasma concentrations of GDF-15 at 36 weeks' gestation were significantly increased among those who developed preeclampsia (P<0.001), area under the receiver operating characteristic curves (AUC) of 0.66 and 0.71, respectively. In cohort 2 a ratio of sFlt-1/PlGF (a clinical biomarker for preeclampsia) had a sensitivity of 61.0% at 83.2% specificity to predict those who will develop preeclampsia (AUC of 0.79). A ratio of GDF-15×sFlt-1/PlGF yielded a sensitivity of 68.3% at 83.2% specificity (AUC of 0.82). GDF-15 was consistently elevated across a number of international cohorts: levels were higher in placenta and blood from women delivering <34 weeks' gestation due to preterm preeclampsia in Melbourne, Australia; and in the blood at 26 to 32 weeks' gestation among 57 women attending the Manchester Antenatal Vascular Service (MAViS, UK) who developed preeclampsia (P=0.0002), compared with 176 controls. In the Preeclampsia Obstetric adVerse Events biobank (PROVE, South Africa), plasma GDF-15 was significantly increased in women with preeclampsia with severe features (P=0.02; n=14) compared to controls (n=14). Conclusions We conclude circulating GDF-15 is elevated among women more likely to develop preeclampsia or diagnosed with the condition. It may have value as a clinical biomarker, including the potential to improve the sensitivity of sFlt-1/PlGF ratio.
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ItemReduced growth velocity from the mid-trimester is associated with placental insufficiency in fetuses born at a normal birthweight.(Biomed Central, 2020-12-24)BACKGROUND: Fetal growth restriction (FGR) due to placental insufficiency is a major risk factor for stillbirth. While small-for-gestational-age (SGA; weight < 10th centile) is a commonly used proxy for FGR, detection of FGR among appropriate-for-gestational-age (AGA; weight ≥ 10th centile) fetuses remains an unmet need in clinical care. We aimed to determine whether reduced antenatal growth velocity from the time of routine mid-trimester ultrasound is associated with antenatal, intrapartum and postnatal indicators of placental insufficiency among term AGA infants. METHODS: Three hundred and five women had biometry measurements recorded from their routine mid-trimester (20-week) ultrasound, at 28 and 36 weeks' gestation, and delivered an AGA infant. Mid-trimester, 28- and 36-week estimated fetal weight (EFW) and abdominal circumference (AC) centiles were calculated. The EFW and AC growth velocities between 20 and 28 weeks, and 20-36 weeks, were examined as predictors of four clinical indicators of placental insufficiency: (i) low 36-week cerebroplacental ratio (CPR; CPR < 5th centile reflects cerebral redistribution-a fetal adaptation to hypoxia), (ii) neonatal acidosis (umbilical artery pH < 7.15) after the hypoxic challenge of labour, (iii) low neonatal body fat percentage (BF%) reflecting reduced nutritional reserve and (iv) placental weight < 10th centile. RESULTS: Declining 20-36-week fetal growth velocity was associated with all indicators of placental insufficiency. Each one centile reduction in EFW between 20 and 36 weeks increased the odds of cerebral redistribution by 2.5% (odds ratio (OR) = 1.025, P = 0.001), the odds of neonatal acidosis by 2.7% (OR = 1.027, P = 0.002) and the odds of a < 10th centile placenta by 3.0% (OR = 1.030, P < 0.0001). Each one centile reduction in AC between 20 and 36 weeks increased the odds of neonatal acidosis by 3.1% (OR = 1.031, P = 0.0005), the odds of low neonatal BF% by 2.8% (OR = 1.028, P = 0.04) and the odds of placenta < 10th centile by 2.1% (OR = 1.021, P = 0.0004). Falls in EFW or AC of > 30 centiles between 20 and 36 weeks were associated with two-threefold increased relative risks of these indicators of placental insufficiency, while low 20-28-week growth velocities were not. CONCLUSIONS: Reduced growth velocity between 20 and 36 weeks among AGA fetuses is associated with antenatal, intrapartum and postnatal indicators of placental insufficiency. These fetuses potentially represent an important, under-recognised cohort at increased risk of stillbirth. Encouragingly, this novel fetal assessment would require only one additional ultrasound to current routine care, and adds to the potential benefits of routine 36-week ultrasound.
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ItemAppropriate-for-gestational-age infants who exhibit reduced antenatal growth velocity display postnatal catch-up growth(PUBLIC LIBRARY SCIENCE, 2020-09-08)BACKGROUND: Postnatally, small-for-gestational-age (SGA; birthweight <10th centile) infants who are growth restricted due to uteroplacental insufficiency (UPI) demonstrate 'catch-up growth' to meet their genetically-predetermined size. Infants who demonstrate slowing growth during pregnancy are those that cross estimated fetal weight centiles at serial ultrasound examinations. These infants that slow in growth but are born appropriate-for-gestational-age (AGA; ≥10th centile), exhibit antenatal, intrapartum and postnatal indicators of UPI. Here, we examine if and when these infants (labelled as AGA-FGR) also demonstrate catch-up growth like SGA infants, when compared with AGA infants with normal antenatal growth velocity (AGA-NG). METHODS: We followed-up the infants of women who had previously undergone ultrasound assessment of fetal size at 28- and 36-weeks' gestation, enabling calculation of antenatal growth velocity. To assess postnatal growth, we asked parents to send their infant's growth measurements, up to two years post-birth, which are routinely collected through the state-wide Maternal-Child Health service. Infants with medical conditions affecting postnatal growth were excluded from the analysis. From the measurements obtained we calculated age-adjusted z-scores for postnatal weight, length and body mass index (BMI; weight(kg)/height(m2)) at birth and 4, 8, 12, 18 and 24 months. We used linear spline regression modelling to predict mean weight, length and BMI z-scores at intervals post birth. Predicted mean age-adjusted z-scores were then compared between three groups; SGA, AGA with low antenatal growth (AGA-FGR; loss of >20 customised estimated fetal weight centiles), and AGA-NG to determine if catch-up growth occurred. In addition, we compared the rates of catch-up growth (defined as an increase in weight age-adjusted z-score of ≥0.67 over 1 year) between the groups with Fisher's exact tests. RESULTS: Of 158 (46%) infant growth records received, 146 were AGA, with low antenatal growth velocity occurring in 34/146 (23.2%). Rates of gestational diabetes and SGA birthweight were higher in those lost to follow-up. Compared to AGA-NG infants, AGA-FGR infants had significantly lower predicted mean weight (p<0.001), length (p = 0.04) and BMI (p = 0.001) z-scores at birth. These significant differences were no longer evident at 4 months, suggesting that catch-up growth had occurred. As expected, the catch-up growth that occurred among the AGA-FGR was not as great in magnitude as that demonstrated by the SGA. When assessed categorically, there was no significant difference between the rate of catch-up growth among the AGA-FGR and the SGA. Catch-up growth was significantly more frequent among both the AGA-FGR and the SGA groups compared to the AGA-NG. CONCLUSIONS: AGA infants that have exhibited reduced antenatal fetal growth velocity also exhibit significant catch-up growth in the first 12 months of life. This finding represents further evidence that AGA fetuses that slow in growth during pregnancy do so due to UPI.
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ItemCirculating SPINT1 is a biomarker of pregnancies with poor placental function and fetal growth restriction(NATURE PUBLISHING GROUP, 2020-05-15)Purpose To investigate the relationship between patient-reported outcome (PRO) questionnaire responses and time to late age-related macular degeneration (AMD; neovascular AMD [nAMD] or multimodal imaging [MMI]-defined atrophy) among individuals with bilateral large drusen, and the prognostic value of baseline PROs for 36-month AMD status. Design Exploratory analyses from a multicenter randomized controlled trial of an AMD intervention (Australian New Zealand Clinical Trials Registry identifier, ACTRN12612000704897). Participants Sham treatment group of the Laser Intervention in Early Stages of Age-Related Macular Degeneration (LEAD) Study (n = 141; age, 50–88 years; 77% female). Methods The 28-item Impact of Vision Impairment (IVI-28) and 10-item Night Vision Questionnaire (NVQ-10) were administered at the baseline visit. The PRO scores were derived using rating scale models. Multivariate Cox regression adjusting for demographics and clinical measures of vision (low-luminance visual acuity, low-luminance deficit, and microperimetric sensitivity) from the poorer-performing eye was used to investigate the association between PRO scores and time to late AMD in either eye. Multivariate competing-risk regression was used to estimate cause-specific subhazard ratios for nAMD and atrophy in either eye. Cross-validated logistic lasso models were used to estimate the predicted probability of AMD at 36 months. The area under the receiver operating characteristic curve was assessed to compare prognostic accuracy between models with and without PROs. Main Outcome Measure Time until nAMD or atrophy in either eye. Results The PRO scores were skewed toward higher functional vision. Higher IVI-28 scores were associated with a lower risk of progression to MMI-defined atrophy (20 events: adjusted hazard ratio, 0.65/logit increase; P = 0.002) but not nAMD (10 events; P = 0.562). Insufficient evidence was found of an association between NVQ-10 score and rate of progression to late AMD (P ≥0.149). Baseline IVI-28 scores were found to contribute to the prognosis of atrophy at the 36-month visit (P = 0.010). Conclusions On average, PROs were associated with an increased risk of progression from intermediate AMD to MMI-defined atrophy. Continuing development of instruments to record PROs in the early stages of AMD have the potential to produce inexpensive and efficient tools to assist in the assessment of disease severity and risk of AMD progression.
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ItemAssessing the sensitivity of placental growth factor and soluble fms-like tyrosine kinase 1 at 36 weeks' gestation to predict small-for-gestational-age infants or late-onset preeclampsia: a prospective nested case-control study(BMC, 2018-08-31)BACKGROUND: Fetal growth restriction is a disorder of placental dysfunction with three to four-fold increased risk of stillbirth. Fetal growth restriction has pathophysiological features in common with preeclampsia. We hypothesised that angiogenesis-related factors in maternal plasma, known to predict preeclampsia, may also detect fetal growth restriction at 36 weeks' gestation. We therefore set out to determine the diagnostic performance of soluble fms-like tyrosine kinase 1 (sFlt-1), placental growth factor (PlGF), and the sFlt-1:PlGF ratio, measured at 36 weeks' gestation, in identifying women who subsequently give birth to small-for-gestational-age (SGA; birthweight <10th centile) infants. We also aimed to validate the predictive performance of the analytes for late-onset preeclampsia in a large independent, prospective cohort. METHODS: A nested 1:2 case-control study was performed including 102 cases of SGA infants and a matched group of 207 controls; and 39 cases of preeclampsia. We determined the diagnostic performance of each angiogenesis-related factor, and of their ratio, to detect SGA infants or preeclampsia, for a predetermined 10% false positive rate. RESULTS: Median plasma levels of PlGF at 36 weeks' gestation were significantly lower in women who subsequently had SGA newborns (178.5 pg/ml) compared to normal birthweight controls (326.7 pg/ml, p < 0.0001). sFlt-1 was also higher among SGA cases, but this was not significant after women with concurrent preeclampsia were excluded. The sensitivity of PlGF to predict SGA infants was 28.8% for a 10% false positive rate. The sFlt-1:PlGF ratio demonstrated better sensitivity for preeclampsia than either analyte alone, detecting 69.2% of cases for a 10% false positive rate. CONCLUSIONS: Plasma PlGF at 36 weeks' gestation is significantly lower in women who subsequently deliver a SGA infant. While the sensitivity and specificity of PlGF currently limit clinical translation, our findings support a blood-based biomarker approach to detect late-onset fetal growth restriction. Thirty-six week sFlt-1:PlGF ratio predicts 69.2% of preeclampsia cases, and could be a useful screening test to triage antenatal surveillance.