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.