Outcome-based comparative analysis of five fetal growth velocity models to define slow growth

OBJECTIVE

Fetal growth surveillance includes assessment of size as well as rate of growth, and various definitions for slow growth have been adopted into clinical use. The aim of this study was to evaluate the effectiveness of different models to identify stillbirth risk, in addition to risk represented by the fetus being small-for-gestational age (SGA).

METHODS

This was a retrospective analysis of a routinely collected and anonymized dataset of pregnancies that had two or more third-trimester ultrasound measurements of estimated fetal weight (EFW). SGA was defined as EFW < 10th customized centile, and slow growth was defined according to five published models in clinical use: (1) a fixed velocity limit of 20 g per day (FVL20 ); (2) a fixed > 50 centile drop, regardless of scan-measurement interval (FCD50 ); (3) a fixed > 30 centile drop, regardless of scan interval (FCD30 ); (4) growth trajectory slower than the third customized growth-centile limit (GCL3 ); and (5) EFW at second scan below the projected optimal weight range (POWR), based on partial receiver-operating-characteristics-curve-derived  cut-offs specific to the scan interval.

RESULTS

The study cohort consisted of 164 718 pregnancies with 480 592 third-trimester ultrasound scans (mean ± SD, 2.9 ± 0.9). The last two scans in each pregnancy were performed at an average gestational age of 33 + 5 and 37 + 1 weeks. At the last scan, 12 858 (7.8%) EFWs were SGA, and of these, 9359 were also SGA at birth (positive predictive value, 72.8%). The rate at which slow growth was defined varied considerably (FVL20 , 12.7%; FCD50 , 0.7%; FCD30 , 4.6%; GCL3 , 19.8%; POWR, 10.1%), and there was varying overlap between cases identified as having slow growth and those identified as SGA at the last scan. Only the POWR method identified additional non-SGA pregnancies with slow growth (11 237/16 671 (67.4%)) that had significant stillbirth risk (relative risk, 1.58 (95% CI, 1.04-2.39)). These non-SGA cases resulting in stillbirth had a median EFW centile of 52.6 at the last scan and a median weight centile of 27.3 at birth. Subgroup analysis identified methodological problems with the fixed-velocity model because it assumes linear growth throughout gestation, and with the centile-based methods because the non-parametric distribution of centiles at the extremes does not reflect actual difference in weight gain.

CONCLUSION

Comparative analysis of five clinically used methods to define slow fetal growth has shown that only the measurement-interval-specific POWR model can identify non-SGA fetuses with slow growth that are at increased risk of stillbirth. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Fetal weight projection model to define growth velocity and validation against pregnancy outcome in a cohort of serially scanned pregnancies

OBJECTIVE

Fetal growth assessment is central to good antenatal care, yet there is a lack of definition of normal and abnormal fetal growth rate which can identify pregnancies at risk of adverse outcome. The aim of this study was to develop and test a model for defining normal limits of growth velocity which are specific to the fetal weight measurement interval.

METHODS

The cohort consisted of 102 138 singleton pregnancies which underwent at least two third-trimester measurements of ultrasound estimated fetal weight (EFW), usually carried out because routine early-pregnancy risk assessment had indicated an increased risk of fetal growth restriction. We projected the EFW from the first of each consecutive measurement pair along its own centile rank to the gestational age of the second scan. Normal growth was defined as the second EFW being within a weight range based on limits derived by partial receiver-operating-characteristics-curve (pROC) analyses for small-for-gestational-age (SGA; < 10^th  centile) and large-for-gestational-age (LGA; > 90^th  centile) birth weight. The limits were measurement-interval specific and calculated for a fixed false-positive rate (FPR) of 10%. The resultant normal, slow and accelerated growth rates calculated from consecutive EFW pairs were evaluated against the following predefined perinatal outcome measures: stillbirth, neonatal death, SGA and LGA at birth, 5-min Apgar score < 7 and admission to the neonatal intensive care unit. Slow growth based on the last two scans was compared with SGA fetal weight (EFW < 10^th  centile) at the last scan and association with stillbirth risk was assessed, expressed as relative risk (RR) with 95% CI.

RESULTS

The optimal cut-off limits for normal growth rate between consecutive scans varied according to the length of the measurement interval, with an average of -8.0% for slow growth and + 9.3% for accelerated growth at a fixed FPR of 10%. Slow growth between random consecutive scan pairs was associated significantly with all predefined outcome measures including stillbirth (RR, 2.19; 95% CI, 1.84-2.53) and neonatal death (RR, 2.28; 95% CI, 1.60-3.13). Accelerated growth was associated with LGA at birth (RR, 2.15; 95% CI, 2.10-2.20), while normal growth was protective of all adverse outcome measures. Slow growth between the last two scans (which were performed at a median gestational age of 33 + 1 to 36 + 4 weeks) and SGA at the last scan were each predictors of stillbirth, and stillbirth risk was highest when both were present (RR, 2.65; 95% CI, 1.67-4.20). However, 66.2% of pregnancies with slow growth were not SGA at the last scan and these cases also had an increased risk of stillbirth (RR, 2.07; 95% CI, 1.40-3.05).

CONCLUSION

Fetal growth velocity defined by projected, measurement-interval specific fetal weight limits is associated independently with perinatal outcome and should be used for antenatal surveillance in addition to assessment by fetal size. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Reduction of stillbirths in England from 2008 to 2017 according to uptake of the Growth Assessment Protocol: 10-year population-based cohort study

OBJECTIVE

Antenatal detection of small-for-gestational age (SGA) can reduce significantly the risk of stillbirth. The Growth Assessment Protocol (GAP) was developed to address the problem that most SGA fetuses are missed antenatally. We set out to analyze the effect that the GAP program has had on stillbirth rates in England.

METHODS

We analyzed data from 2008 (the year before roll-out of the GAP program) to 2017 (latest available Office for National Statistics (ONS) unit-based data). The program consists of five elements: training, evidence-based guidelines for risk assessment and surveillance of fetal growth, customized charts, recording of process and outcome indicators, and audit of missed SGA cases. All maternity units in England were categorized into one of three groups according to their GAP status in 2017: (1) not in the GAP program; (2) GAP implemented partially (incomplete adoption of protocol, no monitoring and audit); and (3) GAP implemented completely. A subset of the complete-implementation group comprised the 20 units with the highest SGA detection rates. Unit-level live-birth and stillbirth data were obtained from the ONS for each of these groups.

RESULTS

Stillbirth rates declined across all groups from 2008 to 2017, and significantly more in units in which GAP was implemented completely than in the non-GAP units (P < 0.05). The steepest decline in stillbirth rate was observed in the 20 units with the highest SGA detection rates, which had a 24% lower stillbirth rate compared with the units not using GAP (P < 0.01) in 2017. This difference remained significant after mixed-effects logistic regression analysis of potential confounding, including social deprivation (odds ratio, 0.76 (95% CI, 0.64-0.90)). Assessment of the nine Bradford Hill causality criteria and associated characteristics suggested that the association between implementation of the GAP program and reduction in stillbirth rate was causal.

CONCLUSIONS

There has been an overall reduction in stillbirth rates in England that is likely to be a result of increased awareness of the importance of antenatal detection of SGA as a key risk factor for stillbirth. The decline in stillbirth rates was significantly greater in maternity units that had fully implemented the GAP program, and was most pronounced in the units with the highest antenatal SGA detection rates. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Customized birthweight standard for an Iranian population

Objective: To produce a customized birthweight standard for Iran.Method: Retrospective study of a pregnancy database collected from five hospitals across Iran. The cohort consisted of 4994 consecutive term births with complete data, delivered between July 2013 and November 2014. Coefficients were derived using a backwards stepwise multiple regression technique.Results: Maternal height, weight in early pregnancy and parity as well as the baby's sex were identified as significant physiological variables affecting birthweight. Paternal height and weight were also significant although weaker factors. The expected 280-day birthweight, free from pathological influences, of a standard size mother (height 163 cm, weight 64 kg) in her first pregnancy was 3390 g. Pathological factors found to affect birthweight in this cohort included village housing, anemia, preexisting and gestational diabetes and preeclampsia.Conclusion: The analysis confirmed the main physiological variables that affect birthweight in other countries and shows paternal factors also to be significant variables. Development of a country-specific customized birthweight standard will aid clinicians in Iran to distinguish between fetuses that are either constitutionally or pathologically small, thereby avoiding unnecessary interventions, and improving identification of at-risk pregnancies and perinatal outcome.

Making stillbirths visible: a systematic review of globally reported causes of stillbirth

BACKGROUND

Stillbirth is a global health problem. The World Health Organization (WHO) application of the International Classification of Diseases for perinatal mortality (ICD-PM) aims to improve data on stillbirth to enable prevention.

OBJECTIVES

To identify globally reported causes of stillbirth, classification systems, and alignment with the ICD-PM.

SEARCH STRATEGY

We searched CINAHL, EMBASE, Medline, Global Health, and Pubmed from 2009 to 2016.

SELECTION CRITERIA

Reports of stillbirth causes in unselective cohorts.

DATA COLLECTION AND ANALYSIS

Pooled estimates of causes were derived for country representative reports. Systems and causes were assessed for alignment with the ICD-PM. Data are presented by income setting (low, middle, and high income countries; LIC, MIC, HIC).

MAIN RESULTS

Eighty-five reports from 50 countries (489 089 stillbirths) were included. The most frequent categories were Unexplained, Antepartum haemorrhage, and Other (all settings); Infection and Hypoxic peripartum (LIC), and Placental (MIC, HIC). Overall report quality was low. Only one classification system fully aligned with ICD-PM. All stillbirth causes mapped to ICD-PM. In a subset from HIC, mapping obscured major causes.

CONCLUSIONS

There is a paucity of quality information on causes of stillbirth globally. Improving investigation of stillbirths and standardisation of audit and classification is urgently needed and should be achievable in all well-resourced settings. Implementation of the WHO Perinatal Mortality Audit and Review guide is needed, particularly across high burden settings.

FUNDING

HR, SH, SHL, and AW were supported by an NHMRC-CRE grant (APP1116640). VF was funded by an NHMRC-CDF (APP1123611).

TWEETABLE ABSTRACT

Urgent need to improve data on causes of stillbirths across all settings to meet global targets.

PLAIN LANGUAGE SUMMARY

Background and methods Nearly three million babies are stillborn every year. These deaths have deep and long-lasting effects on parents, healthcare providers, and the society. One of the major challenges to preventing stillbirths is the lack of information about why they happen. In this study, we collected reports on the causes of stillbirth from high-, middle-, and low-income countries to: (1) Understand the causes of stillbirth, and (2) Understand how to improve reporting of stillbirths. Findings We found 85 reports from 50 different countries. The information available from the reports was inconsistent and often of poor quality, so it was hard to get a clear picture about what are the causes of stillbirth across the world. Many different definitions of stillbirth were used. There was also wide variation in what investigations of the mother and baby were undertaken to identify the cause of stillbirth. Stillbirths in all income settings (low-, middle-, and high-income countries) were most frequently reported as Unexplained, Other, and Haemorrhage (bleeding). Unexplained and Other are not helpful in understanding why a baby was stillborn. In low-income countries, stillbirths were often attributed to Infection and Complications during labour and birth. In middle- and high-income countries, stillbirths were often reported as Placental complications. Limitations We may have missed some reports as searches were carried out in English only. The available reports were of poor quality. Implications Many countries, particularly those where the majority of stillbirths occur, do not report any information about these deaths. Where there are reports, the quality is often poor. It is important to improve the investigation and reporting of stillbirth using a standardised system so that policy makers and healthcare workers can develop effective stillbirth prevention programs. All stillbirths should be investigated and reported in line with the World Health Organization standards.

Application of ICD-PM to preterm-related neonatal deaths in South Africa and United Kingdom

OBJECTIVE

We explore preterm-related neonatal deaths using the WHO application of the International Classification of Disease (ICD-10) to deaths during the perinatal period: ICD-PM as an informative case study, where ICD-PM can improve data use to guide clinical practice and programmatic decision-making.

DESIGN

Retrospective application of ICD-PM.

SETTING

South Africa, and the UK.

POPULATION

Perinatal death databases.

METHODS

Descriptive analysis of neonatal deaths and maternal conditions present.

MAIN OUTCOME MEASURES

Causes of preterm neonatal mortality and associated maternal conditions.

RESULTS

We included 98 term and 173 preterm early neonatal deaths from South Africa, and 956 term and 3248 preterm neonatal deaths from the UK. In the South African data set, the main causes of death were respiratory/cardiovascular disorders (34.7%), low birthweight/prematurity (29.2%), and disorders of cerebral status (25.5%). Amongst preterm deaths, low birthweight/prematurity (43.9%) and respiratory/cardiovascular disorders (32.4%) were the leading causes. In the data set from the UK, the leading causes of death were low birthweight/prematurity (31.6%), congenital abnormalities (27.4%), and deaths of unspecified cause (26.1%). In the preterm deaths, the leading causes were low birthweight/prematurity (40.9%) and deaths of unspecified cause (29.6%). In South Africa, 61% of preterm deaths resulted from the maternal condition of preterm spontaneous labour. Among the preterm deaths in the data set from the UK, no maternal condition was present in 36%, followed by complications of placenta, cord, and membranes (23%), and other complications of labour and delivery (22%).

CONCLUSIONS

ICD-PM can be used to appraise the maternal and newborn conditions contributing to preterm deaths, and can inform practice.

TWEETABLE ABSTRACT

ICD-PM can be used to appraise maternal and newborn contributors to preterm deaths to improve quality of care.

The WHO application of ICD-10 to deaths during the perinatal period (ICD-PM): results from pilot database testing in South Africa and United Kingdom

OBJECTIVE

To apply the World Health Organization (WHO) Application of the International Classification of Diseases, tenth revision (ICD-10) to deaths during the perinatal period: ICD-Perinatal Mortality (ICD-PM) to existing perinatal death databases.

DESIGN

Retrospective application of ICD-PM.

SETTING

South Africa, UK.

POPULATION

Perinatal death databases.

METHODS

Deaths were grouped according to timing of death and then by the ICD-PM cause of death. The main maternal condition at the time of perinatal death was assigned to each case.

MAIN OUTCOME MEASURES

Causes of perinatal mortality, associated maternal conditions.

RESULTS

In South Africa 344/689 (50%) deaths occurred antepartum, 11% (n = 74) intrapartum and 39% (n = 271) in the early neonatal period. In the UK 4377/9067 (48.3%) deaths occurred antepartum, with 457 (5%) intrapartum and 4233 (46.7%) in the neonatal period. Antepartum deaths were due to unspecified causes (59%), chromosomal abnormalities (21%) or problems related to fetal growth (14%). Intrapartum deaths followed acute intrapartum events (69%); neonatal deaths followed consequences of low birthweight/ prematurity (31%), chromosomal abnormalities (26%), or unspecified causes in healthy mothers (25%). Mothers were often healthy; 53%, 38% and 45% in the antepartum, intrapartum and neonatal death groups, respectively. Where there was a maternal condition, it was most often maternal medical conditions, and complications of placenta, cord and membranes.

CONCLUSIONS

The ICD-PM can be a globally applicable perinatal death classification system that emphasises the need for a focus on the mother-baby dyad as we move beyond 2015.

TWEETABLE ABSTRACT

ICD-PM is a global system that classifies perinatal deaths and links them to maternal conditions.

Optimising the International Classification of Diseases to identify the maternal condition in the case of perinatal death

OBJECTIVE

The WHO application of the tenth edition of the International Classification of Diseases (ICD-10) to deaths during the perinatal period (ICD Perinatal Mortality, ICD-PM) captures the essential characteristics of the mother-baby dyad that contribute to perinatal deaths. We compare the capture of maternal conditions in the existing ICD-PM with the maternal codes from the WHO application of ICD-10 to deaths during pregnancy, childbirth, and the puerperium (ICD Maternal Mortality, ICD-MM) to explore potential benefits in the quality of data received.

DESIGN

Retrospective application of ICD-PM.

SETTING

South Africa and the UK.

POPULATION

Perinatal death databases.

METHODS

The maternal conditions were classified using the ICD-PM groupings for maternal condition in perinatal death, and then mapped to the ICD-MM groupings of maternal conditions.

MAIN OUTCOME MEASURES

Main maternal conditions in perinatal deaths.

RESULTS

We reviewed 9661 perinatal deaths. The largest group (4766 cases, 49.3%) in both classifications captures deaths where there was no contributing maternal condition. Each of the other ICD-PM groups map to between three and six ICD-MM groups. If the cases in each ICD-PM group are re-coded using ICD-MM, each group becomes multiple, more specific groups. For example, the 712 cases in group M4 in ICD-PM become 14 different and more specific main disease categories when the ICD-MM is applied instead.

CONCLUSIONS

As we move towards ICD-11, the use of the more specific, applicable, and relevant codes outlined in ICD-MM for both maternal deaths and the maternal condition at the time of a perinatal death would be preferable, and would provide important additional information about perinatal deaths.

TWEETABLE ABSTRACT

Improving the capture of maternal conditions in perinatal deaths provides important actionable information.

Effectiveness of folic acid supplementation in pregnancy on reducing the risk of small-for-gestational age neonates: a population study, systematic review and meta-analysis

OBJECTIVES

To assess the effect of timing of folic acid (FA) supplementation during pregnancy on the risk of the neonate being small for gestational age (SGA).

DESIGN

A population database study and a systematic review with meta-analysis including the results of this population study.

SETTING AND DATA SOURCES

A UK regional database was used for the population study and an electronic literature search (from inception until August 2013) for the systematic review.

PARTICIPANTS AND INCLUDED STUDIES

Singleton live births with no known congenital anomalies; 111,736 in population study and 188,796 in systematic review.

OUTCOME MEASURES, DATA EXTRACTION AND ANALYSIS

The main outcome was SGA based on customised birthweight centile. Associations are presented as odds ratios (OR) and adjusted odds ratios (aOR), adjusted for maternal and pregnancy-related characteristics.

RESULTS

Of 108,525 pregnancies with information about FA supplementation, 92,133 (84.9%) had taken FA during pregnancy. Time of commencement of supplementation was recorded in 39,416 pregnancies, of which FA was commenced before conception in 10,036, (25.5%) cases. Preconception commencement of FA supplementation was associated with reduced risk of SGA <10th centile (aOR 0.80, 95% CI 0.71-0.90, P < 0.01) and SGA <5th centile (aOR 0.78, 95% CI 0.66-0.91, P < 0.01). This result was reproduced when the data were pooled with other studies in the systematic review, showing a significant reduction in SGA (<5th centile) births with preconception commencement of FA (aOR 0.75, 95% CI 0.61-0.92, P < 0.006). In contrast, postconception folate had no significant effect on SGA rates.

CONCLUSION

Supplementation with FA significantly reduces the risk of SGA at birth but only if commenced preconceptually independent of other risk factors.

SYSTEMATIC REVIEW REGISTRATION

This systematic review was prospectively registered with PROSPERO number CRD42013004895.

The experience of the implementation of perinatal audit in Moldova

The Beyond the Numbers project in Moldova implemented perinatal mortality audit as a means to improve maternity and newborn care. Key activities for this project included training in audit, the setting up of audit committees, implementation of the review of cases and dissemination of information. During the project, a significant reduction was noted of perinatal deaths at term (from 37 weeks gestation and birthweight of ≥2500 g) by 1.5 per 1000; from 5.1 per 1000 in 2006 to 3.6 per 1000 in 2013.

Preventing stillbirths through improved antenatal recognition of pregnancies at risk due to fetal growth restriction

Most stillbirths used to be categorized as 'unexplained' and were considered, by implication, unavoidable. Recent evidence indicates that they represent a combined challenge for public health and for clinical services. Independent case reviews have found that many deaths are associated with a failure to recognize risk factors and to afford them the appropriate standard of care. The majority of normally formed fetal deaths had preceding, unrecognized intrauterine growth failure. Improved training and adoption of standardized protocols has led to increased antenatal detection of fetal growth restriction, and this in turn has resulted in significant reductions in stillbirths in areas with high uptake of the training programme. A comprehensive, evidence-based growth assessment protocol (GAP) is currently being rolled out across the NHS to implement this strategy for stillbirth prevention.

Development and evaluation of a standardized registry for diabetes in pregnancy using data from the Northern, North West and East Anglia regional audits

OBJECTIVES

To develop and evaluate a standardized data set for measuring pregnancy outcomes in women with Type 1 and Type 2 diabetes and to compare recent outcomes with those of the 2002-2003 Confidential Enquiry into Maternal and Child Health.

METHODS

Existing regional, national and international data sets were compared for content, consistency and validity to develop a standardized data set for diabetes in pregnancy of 46 key clinical items. The data set was tested retrospectively using data from 2007-2008 pregnancies included in three regional audits (Northern, North West and East Anglia). Obstetric and neonatal outcomes of pregnancies resulting in a stillbirth or live birth were compared with those from the same regions during 2002-2003.

RESULTS

Details of 1381 pregnancies, 812 (58.9%) in women with Type 1 diabetes and 556 (40.3%) in women with Type 2 diabetes, were available to test the proposed standardized data set. Of the 46 data items proposed, only 16 (34.8%), predominantly the delivery and neonatal items, achieved ≥ 85% completeness. Ethnic group data were available for 746 (54.0%) pregnancies and BMI for 627 (46.5%) pregnancies. Glycaemic control data were most complete-available for 1217 pregnancies (88.1%), during the first trimester. Only 239 women (19.9%) had adequate pregnancy preparation, defined as pre-conception folic acid and first trimester HbA(1c) ≤ 7% (≤ 53 mmol/mol). Serious adverse outcome rates (major malformation and perinatal mortality) were 55/1000 and had not improved since 2002-2003.

CONCLUSIONS

A standardized data set for diabetes in pregnancy may improve consistency of data collection and allow for more meaningful evaluation of pregnancy outcomes in women with pregestational diabetes.

The value of customised centiles in assessing perinatal mortality risk associated with parity and maternal size

OBJECTIVE

We wanted to compare customised and population standards for defining smallness for gestational age (SGA) in the assessment of perinatal mortality risk associated with parity and maternal size.

DESIGN

Population-based cohort study.

SETTING

Sweden.

POPULATION

Swedish Birth Registry database 1992-1995 with 354 205 complete records.

METHOD

Coefficients were derived and applied to determine SGA by the fully customised method, or by adjustment for fetal sex only, and using the same fetal weight standard.

MAIN OUTCOME MEASURE

Perinatal deaths and rates of small for gestational age (SGA) babies within subgroups stratified by parity, body mass index (BMI) and maternal size within the BMI range of 20.0-24.9.

RESULTS

Perinatal mortality rates (PMR) had a U-shaped distribution in parity groups, increased proportionately with maternal BMI, and had no association with maternal size within the normal BMI range. For each of these subgroups, SGA rates determined by the customised method showed strong association with the PMR. In contrast, SGA based on uncustomised, population-based centiles had poor correlation with perinatal mortality. The increased perinatal mortality risk in pregnancies of obese mothers was associated with an increased risk of SGA using customised centiles, and a decreased risk of SGA using population-based centiles.

CONCLUSION

The use of customised centiles to determine SGA improves the identification of pregnancies which are at increased risk of perinatal death.

Birth weight and long-term metabolic outcomes: does the definition of smallness matter?

OBJECTIVE

To establish the role of individual definition of smallness at birth in the association between birth weight and long-term metabolic outcomes.

METHODS

Lipid profile and oral glucose tolerance test were performed in young adults (22 years) born either small (SGA) or appropriate for gestational age (AGA). AGA/SGA were defined by both population-based and customized methods adjusting for individual maternal/pregnancy characteristics. 825 individuals were classified as AGA and 575 as SGA by both methods, 131 were SGA by the population-based method only (SGA(pop)) and 22 were SGA by the customized method only (SGA(cust)).

RESULTS

SGA(cust) subjects had higher total cholesterol and triglyceride levels and lower high-density lipoprotein cholesterol concentrations than SGA(pop) and AGA subjects, however, insignificantly when adjusted for age, gender and body mass index. The homeostasis model assessment for insulin resistance (HOMA-IR) index was higher in the SGA(cust) (p = 0.05) and SGA(pop) (p = 0.02) versus the AGA group. Controlling for the HOMA-IR index, the insulinogenic index was significantly lower in the SGA(cust) versus SGA(pop) (p = 0.001) and AGA (p = 0.003) groups. In SGA(cust) individuals, the HOMA-IR index was clearly shifted to higher, while the insulinogenic index to lower tertiles of AGA distribution; SGA(pop) subjects had the HOMA-IR and insulinogenic index predominantly in the highest tertiles.

CONCLUSIONS

Individualized birth weight standards allow to better identify subjects who failed to reach their genetic potential of intrauterine growth and are at higher risk of metabolic disturbances and impaired insulin secretion later in life.

Cerebral palsy and restricted growth status at birth: population-based case-control study

OBJECTIVE

To evaluate the association between growth status at birth and subsequent development of cerebral palsy in preterm and term infants.

DESIGN

Population-based case-controlled study.

SETTING

Cerebral palsy register in Western Sweden. Subjects Cohort of 334 singletons born between 1983 and 1990, with cerebral palsy diagnosed from age 4, and 668 singletons matched for gestation, gender and delivery unit.

METHOD

Growth status at birth was determined using small for gestational age (SGA) categories, with customised birthweight percentiles (SGAcust) based on the Swedish population.

MAIN OUTCOME MEASURES

Proportion of babies that were SGAcust, comparing cases and controls in three gestational age categories: early preterm (24-33 weeks), late preterm (34-36 weeks) and term (37+ weeks).

RESULTS

Of the 334 children with cerebral palsy, 87 (26.6%) were born early preterm, 27 (8.1%) late preterm and 218 (66%) at term. Children who had been born at term were more likely to have been SGA <1st customised percentile (SGAcust1) than their matched controls (OR 6.6, 95% CI 2.3-18.6). In contrast, children with cerebral palsy born preterm were not more likely to have been SGAcust1 (OR 0.9, 95% CI 0.4-1.9), and this applied to early preterm as well as late preterm births. For less severely small babies (SGA between 1st and 5th customised percentiles), the association with cerebral palsy remained significant for term births (OR 5.2, 95% CI 2.7-10.1) but was again not significant for preterm births.

CONCLUSIONS

Term singletons with severely SGA birthweights had a five- to seven-fold risk of developing cerebral palsy compared with gestational age-matched infants with birthweights within normal limits. For children born preterm, SGA was not more likely to be present in cases than in controls. These findings support the concept of cerebral palsy as a multifactorial condition and highlight the importance of antenatal surveillance of fetal growth.

Predictiveness of antenatal umbilical artery Doppler for adverse pregnancy outcome in small-for-gestational-age babies according to customised birthweight centiles: population-based study

OBJECTIVE

To examine the relationship between smallness at birth and the predictive value of umbilical artery Doppler.

DESIGN

Retrospective cohort.

SETTING

Tertiary referral university hospital, Barcelona.

POPULATION

A total of 7645 singleton pregnancies delivered between January 2002 and June 2004.

METHODS

The associations with adverse outcome were assessed for small-for-gestational-age (SGA) babies according to customised standards who had normal and abnormal umbilical artery Doppler.

MAIN OUTCOME MEASURES

Neonatal morbidity and perinatal mortality.

RESULTS

Of the 369 SGA fetuses that had been identified antenatally, 70 (19%) had an abnormal umbilical artery Doppler and the babies from these pregnancies had a higher risk for neonatal morbidity when compared with babies with normal birthweight (OR 3.99, 95% CI 1.04-11.03). However, the remaining 299 (81%) fetuses with normal umbilical artery Doppler also had an elevated risk of neonatal morbidity (OR 2.26, 95% CI 1.04-4.39). Overall, many of the instances of adverse outcome associated with smallness for gestational age were attributable to the group with normal Doppler than to the group with abnormal Doppler.

CONCLUSION

Normal antenatal umbilical artery Doppler cannot be taken as an indicator of low risk in pregnancies where the fetus is SGA according to customised percentiles.

Customized birthweight standards for a Spanish population

OBJECTIVE

To analyse the biological factors affecting birthweight and to derive customized birthweight standards for a Spanish population.

METHODS

A retrospective cohort was created with all the singleton pregnancies delivered at term and free of pathology in our Institution. Birthweight was modeled by multiple linear regression from maternal (ethnic origin, maternal height, booking weight, smoking, and parity), and fetal (gender, gestational age) characteristics.

RESULTS

In addition to gestational age and sex, height, booking weight, ethnic origin, parity, and smoking all have significant and independent effects on birthweight. Women from East-Asia, Morocco and South-America had newborns on average 83 g, 74 g and 95 g heavier than White-European Spanish women. The effect of smoking was found to be dose-related.

CONCLUSION

We found the relative effect of the maternal and fetal characteristics to be very similar to that reported in previous studies. We report coefficients for ethnic groups that account for a sizeable proportion of the population composition of several European countries.

Association of smoking during pregnancy and fetal growth restriction: subgroups of higher susceptibility

OBJECTIVE

To analyze the association between maternal smoking and fetal growth restriction, defined as a failure to achieve the growth potential, and to define subgroups of higher susceptibility for this association.

STUDY DESIGN

A definition of growth restriction by customized birthweight standards applied to 13,661 non-malformed singleton deliveries. Customization was performed by maternal ethnic origin, height, booking weight, parity, gestational age at delivery and fetal gender. The adjusted risk of smoking for customized smallness-for-gestational age and the identification of subgroups with higher susceptibility were assessed by logistic regression.

RESULTS

Overall, the adjusted odds ratio of smoking (all levels of exposure grouped) for the occurrence of growth restriction was 1.9 (95% confidence interval: 1.69-2.13). Smoking was etiologically responsible for 13.9% (95% confidence interval: 11.2-16.5) of the cases of growth restriction occurring in the population. Smoking resulted in an increasingly greater risk of growth restriction with progressive levels of cigarette consumption. The risk of smoking for fetal growth restriction was significantly greater in older women and those with a previous history of spontaneous preterm delivery.

CONCLUSIONS

Smoking is associated with a higher risk for growth restriction. In addition, older pregnant women and those with a previous history of preterm delivery have an increased susceptibility.

New Definition of Small for Gestational Age Based on Fetal Growth Potential

Accurate definition of small for gestational age (SGA) is essential for antenatal as well as postnatal care. SGA is associated with significant antenatal and postnatal pathology. The term, however, includes constitutional smallness, and it is essential to adjust for physiological variation in order to identify those babies who are pathologically small. Maternal height, weight, parity, ethnic origin and the baby's gender have all been found to be significantly associated with normal variation in birth weight. These variables need to be adjusted for to calculate the true growth potential, which can be represented as individually customized fetal growth curves and birth weight percentiles (www.gestation.net). This method for calculating growth potential has been validated in a number of international studies. 'Customized SGA' defines neonates with intrauterine growth restriction, while 'small-normal' does not represent increased risk. Currently, coefficients are being developed for more ethnic groups, to broaden the international applicability of individualized standards. Work is also underway to incorporate the customized birth weight percentile as the starting point of infant growth curves.

Perinatal outcome in SGA births defined by customised versus population-based birthweight standards

OBJECTIVE

To determine whether customised birthweight standard improves the definition of small for gestational age and its association with adverse pregnancy outcomes such as stillbirth, neonatal death, or low Apgar score.

DESIGN

Population based cohort study.

POPULATION

Births in Sweden between 1992-95 (n = 326,377).

METHODS

Risks of stillbirth, neonatal death, and Apgar score under four at five minutes were calculated for the lowest 10% birthweights according to population-based and customised standards, and were compared with the data from the group with birthweights over this limit. Population attributable risks for stillbirth using various birthweight centile cutoffs were calculated for the two standards.

OUTCOME MEASURES

Odds ratios and 95% confidence intervals for stillbirth, neonatal death and Apgar score under four at five minutes, and population attributable risks for stillbirth at different birthweight centiles.

RESULTS

Risks of stillbirth, neonatal death, and Apgar score under four at five minutes and population attributable risks of stillbirth were consistently higher if 'small for gestational age' was classified by a customised rather than by the population-based birthweight standard. Compared with infants who were not small for gestational age by both standards, the odds ratio for stillbirth was 6.1 (95% CI 5.0-7.5) for small for gestational age by customised standard only, whereas it was 1.2 (95 % CI 0.8-1.9) for small for gestational age by population standard only.

CONCLUSIONS

Compared with the population-based birthweight standard, a customised birthweight standard increases identification of fetuses at risk of stillbirth, neonatal death and Apgar score under 4 at 5 minutes, probably due to improved identification of fetal growth restriction.

Fetal growth

Recent epidemiological and experimental studies show that abnormal fetal growth can lead to serious complications, including stillbirth, perinatal morbidity and disorders extending well beyond the neonatal period. It is now clear that the intrauterine milieu is as important as genetic endowment in shaping the future health of the conceptus. Maternal characteristics such as weight, height, parity and ethnic group need to be adjusted for, and pathological factors such as smoking excluded, to establish appropriate standards and improve the distinction between what is normal and abnormal. Currently, the aetiology of growth restriction is not well understood and preventative measures are ineffective. Elective delivery remains the principal management option, which emphasizes the need for better screening techniques for the timely detection of intrauterine growth failure.

Early pregnancy predictors of preterm birth: the role of a prolonged menstruation-conception interval

OBJECTIVE

To study early pregnancy characteristics as possible risk factors associated with preterm birth.

DESIGN

Retrospective analysis of prospectively collected maternity data.

POPULATION

21,069 singleton deliveries with record of a specified last menstrual period and a midtrimester dating scan.

SETTING

Catchment area of tertiary centre serving a general maternity population.

METHODS

Univariate and multivariate analysis. Variables included: maternal age; height; weight at first visit; parity; ethnic group; cigarette smoking and alcohol consumption recorded in early pregnancy; history of abortion; history of preterm birth; and discrepancy between menstrual dates and ultrasound dates.

MAIN OUTCOME MEASURES

Adjusted odds ratios for factors associated with preterm birth, stratified according to parity (nulliparae vs multiparae) and gestational age (early preterm, 24-33 weeks; late preterm, 34-36 weeks; all preterm, < 37 weeks). Population attributable risk (aetiologic fraction) of the significant variables for preterm birth.

RESULTS

The overall preterm (< 37 weeks) delivery rate according to scan dates was 7 x 0%. Preterm birth was associated with young (< 20 years), short (< or = 155 cm) and underweight (< or = 52 kg) mothers, non-Europeans, cigarette smokers, previous abortion or previous preterm delivery, and a prolonged menstruation-conception interval. Preterm births which followed the spontaneous onset of labour (72%) had results which were similar to the overall group, while there were too few iatrogenic preterm deliveries for separate analysis. Logistic regression showed that associations varied in different parity and gestational age groups. For nulliparae, smoking was not associated with preterm birth, but it was strongly associated with multiparous women (adjusted OR 1 x 8, 95% CI 1 x 6-2 x 1). A past history of premature delivery had the highest risk for birth before 34 weeks in the index pregnancy (adjusted OR 5 x 1, 95% CI 3 x 4-7 x 6). A discrepancy between menstrual and scan dates of greater than +7 days, suggestive of a prolonged interval between last menstruation and conception, was present in 23 x 3% of all pregnancies, and was associated with an increased risk of preterm delivery in all gestational age categories for nulliparae (adjusted OR 1 x 5, 95% CI 1 x 3-1 x 8) and multiparae (adjusted OR 1 x 9, 95% CI 1 x 6-2 x 2). Because of its high prevalence, this variable constituted a relatively high population-attributable risk for premature birth for both nulliparae (10 x 7%) and multiparae (16 x 6%).

CONCLUSIONS

A discrepancy of more than +7 days between menstrual and scan dates, indicating a prolonged interval between last menstruation and conception, is a significant predictor of preterm birth. This effect is independent of other factors such as maternal age, height, weight and smoking which are also associated with prematurity. In a maternity population with ultrasound scan dates and recorded last menstrual period, this variable can be easily calculated and used as a marker for increased surveillance.

Customized fetal weight limits for antenatal detection of fetal growth restriction

OBJECTIVE

To define cut-off limits for individually adjustable fetal weight standards for the detection of intrauterine growth restriction.

DESIGN

Retrospective study, with the outcome measures small-for-gestational age (SGA) birth weight, operative delivery for fetal distress, umbilical artery pH < 7.15, and admission to the neonatal intensive care unit.

SUBJECTS AND METHODS

Two hundred and fifteen women considered to be at increased risk of uteroplacental insufficiency were recruited to a study of serial ultrasound scans. Fetal weights were derived using standard formulae and, retrospectively, weight percentiles were calculated after individual adjustment for maternal height, weight in early pregnancy, ethnic group, parity and fetal sex.

INTRODUCTION

One or more antenatal scans indicative of fetal weight below the 10th customized percentile were predictive for a SGA neonate at birth (P < 0.001), operative delivery for fetal distress (P < 0.01) and admission to neonatal intensive care (P < 0.01) but not for a low umbilical artery pH (P = 0.6). Receiver-operator curves showed the optimal customized fetal weight percentile limit for predicting an SGA neonate to be the 18th percentile (sensitivity 83%, specificity 79%, positive predictive value 63% and negative predictive value 92%). For the prediction of operative delivery for fetal distress and admission to neonatal intensive care, the optional customized cut-off value was the 8th percentile.

CONCLUSIONS

The assessment of fetal weight using ultrasound and an individually-adjusted standard is predictive of growth restriction and perinatal events associated with hypoxia or diminished reserve. The optimal cut-off value for predicting operative delivery for fetal distress or admission to the neonatal intensive care unit suggests that the 10th customized percentile is a good limit for clinical use.

Symphysis-fundus height and pregnancy characteristics in ultrasound-dated pregnancies

OBJECTIVE

To investigate the relation between maternal and pregnancy characteristics and symphysis-fundus height values at term in an obstetric population dated by sonography.

METHODS

Three hundred twenty-five women were recruited from the antenatal clinics of the Queen's Medical Centre, Nottingham, United Kingdom for measurement of fundal height and for ultrasound scans. Symphysis-fundus height measurements were analyzed by multivariate regression analysis in relation to gestational age, maternal height and weight, ethnic group, and smoking.

RESULTS

Gestational age and maternal characteristics explained nearly half of the variability in symphysis-fundus height. Gestational age was the most important determinant, followed by maternal weight, parity, and sex of the infant. The other variables were not significantly correlated.

CONCLUSION

Maternal characteristics had statistically significant effects on the expected symphysis-fundus height, which suggests that individually adjusted fundal height charts may improve the precision of clinical screening for fetal growth restriction.

Controlled trial of fundal height measurement plotted on customised antenatal growth charts

OBJECTIVE

The purpose of this study was to evaluate the effect of a policy of standard antenatal care which included plotting fundal height measurements on customised antenatal charts in the community.

DESIGN

Prospective, non-randomised, controlled, population-based study.

POPULATION

Two defined and separate referral areas from community to teaching hospital, with similar delivery rates and socioeconomic characteristics. A total of 1272 consecutively booked women with singleton pregnancies and dating ultrasound scans before 22 weeks of gestation.

INTERVENTION

In the study area customised fundal height charts were issued to each mother at the routine hospital booking scan, on which regular fundal height measurements were to be plotted by community midwives. The charts adjusted limits according to maternal characteristics including height, weight, parity and ethnic group. Usual management in the control area included fundal height assessment by abdominal palpation and recording on a standard co-operation card.

OUTCOME MEASURES

Antenatal detection of small and large for gestational age babies; number of antenatal investigations for fetal growth in each group.

RESULTS

The study group had a significantly higher antenatal detection rate of small for gestational age babies (48% vs 29%, odds ratio 2.2, 95% confidence interval 1.1-4.5) and large for gestational age babies (46% vs 24%, OR 2.6, CI 1.3-5.5). There was no increase in the study group in the overall number of scans per pregnancy done in the ultrasound department (1.2 vs 1.3, P = 0.14), but a slight decrease in repeat (two or more) third trimester scans (OR 0.8, CI 0.6-1.0, P = 0.08). Women in the study group had significantly fewer referrals for investigation in a pregnancy assessment centre (OR 0.7, CI 0.5-0.9; P = 0.01) and fewer admissions to the antenatal ward (OR 0.6, CI 0.4-0.7, P < 0.001). There were no differences in perinatal outcome.

CONCLUSIONS

Serial measurement of fundal height plotted on customised charts leads to increased antenatal detection of small and large babies. This is accompanied by fewer investigations, which is likely to represent increased confidence in the community to recognise normal fetal growth. With adjustments for physiological variables, fundal height measurements appear to be a cost effective screening method which can result in substantial improvements in the antenatal assessment of fetal growth.

Fetal growth rate and adverse perinatal events

OBJECTIVE

To study fetal weight gain and its association with adverse perinatal events in a serially scanned high-risk population.

SUBJECTS AND METHODS

A total of 200 pregnant women considered at increased risk of uteroplacental insufficiency had a total of 1140 scans in the third trimester, with a median of six scans in each pregnancy. The average fetal growth rate was retrospectively calculated for the last 6 weeks to birth, and expressed as daily weight gain in grams per day. Adverse pregnancy outcome was defined as operative delivery for fetal distress, acidotic umbilical artery pH (< 7.15), or admission to the neonatal intensive care unit (NICU).

RESULTS

Fetuses with normal outcome in this high-risk pregnancy population had an average antenatal growth rate of 24.2 g/day. Compared to pregnancies with normal outcome, the growth rate was slower in those that required operative delivery for fetal distress (20.9 g/day, p < 0.05) and those that required admission to the NICU (20.3 g/day, p < 0.05). The growth rate in pregnancies resulting in acidotic umbilical artery pH also seemed lower, but this did not reach statistical significance.

CONCLUSIONS

Impaired fetal weight gain prior to birth is associated with adverse perinatal events suggestive of growth failure.

The application of individualised fetal growth curves

Individually adjusted or 'customised' growth charts aim to optimise the assessment of fetal growth by taking individual variation into account, and by projecting an optimal curve which delineates the potential weight gain in each pregnancy. This results in an increased detection rate of true growth restriction and a reduction in false positive diagnoses for IUGR. An adjustable standard can apply across geographical boundaries, as individual variation exceeds that between different maternity populations.

The application of individualised fetal growth curves

Individually adjusted or 'customised' growth charts aim to optimise the assessment of fetal growth by taking individual variation into account, and by projecting an optimal curve which delineates the potential weight gain in each pregnancy. This results in an increased detection rate of true growth restriction and a reduction in false positive diagnoses for IUGR. An adjustable standard can apply across geographical boundaries, as individual variation exceeds that between different maternity populations.

Application of a customised birthweight standard in the assessment of perinatal outcome in a high risk population

OBJECTIVE

Physiological as well as pathological variables influence birthweight. The aim of the present study was to examine perinatal outcome in relation to birthweight centiles applying a customised birthweight standard.

METHODS

Two hundred and seventeen babies from high risk pregnancies were evaluated and classified as small or not small for gestational age according to two standards: 1. conventional Dutch birthweight centiles and 2. customised centiles which adjust individually for physiological variables like maternal booking weight, height and ethnic origin.

RESULTS

Customisation of the weight standards resulted in identification of an additional group of infants who were small for gestational age, but not by the Dutch standards. These babies were associated with significantly more adverse perinatal events than those who were not small for gestational age as defined by a customised standard.

CONCLUSIONS

Adjustment of birthweight centiles for physiological variables significantly improves the identification of infants who have failed to reach the expected birthweight and who are at increased risk for adverse perinatal events.

Analysis of birthweight and gestational age in antepartum stillbirths

OBJECTIVE

To study the characteristics of birthweight and gestational age of third trimester fetal deaths which occurred before the onset of labour.

DESIGN

Review of computerised confidential perinatal mortality records. Data originated from the 1992 Trent Region Perinatal Mortality Survey.

SAMPLE

One hundred and forty-nine antepartum stillbirths of at least 24 weeks of gestation confirmed by early ultrasound scan. Congenital abnormalities and multiple pregnancies were excluded.

MAIN OUTCOME MEASURES

Reported causes of stillbirth; weight-for-gestational age centiles based on a standard derived from normal pregnancies; pregnancy characteristics compared with the local maternity population.

RESULTS

Of 149 stillbirths, 83 (56%) were preterm and 66 were at term, and the majority (126; 85%) occurred from 31 weeks. Most of the deaths (97; 65%) were reported as 'unexplained' even though post-mortems had been carried out in 60% of all cases. Using a gestational age-specific fetal weight standard derived from normal, term live births, 41% of all cases of stillborn infants were small-for-gestational age (< 10th centile; OR 6.2; 95% CI 3.3-11.5); 39% of which had been classified as unexplained were small for gestational age (OR 5.6; 2.6-12.0). This excess of small stillbirths was most pronounced between 31 and 33 weeks, where the weights of 63% of all stillbirths and 72% of unexplained fetal deaths were < 10th centile. Overall, a higher proportion of preterm (< 37 weeks) than term stillbirths were small for gestational age: 53% vs 26% (OR 3.3; 1.6-6.5). However, at term there were also more subtle differences in weight deficit, with more fetuses with a weight between the 10th and 50th centiles than between 50th and 90th (36 vs 11; OR 3.3; 1.4-7.8). Mothers of pregnancies ending in stillbirth were similar in age, size, parity and ethnic group to mothers of live born babies, but were more likely to be smokers (37 vs 27%, OR 1.6; 1.2-2.3).

CONCLUSIONS

Many stillborn babies are small for gestational age. In the absence of significant differences in physiological pregnancy characteristics, this is unlikely to be a constitutional smallness, but represents a preponderance of intrauterine growth restriction. For a full appreciation of the strength of this association, appropriate weight standards and classifications need to be applied in perinatal mortality surveys. Many antepartum stillbirths which are currently designated as unexplained may be avoidable if slow fetal growth could be recognised as a warning sign.