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.     

Customised birthweight centiles are useful for identifying small-for-gestational-age babies in women with type 2 diabetes

Background: Customised birthweight centiles identify small-for-gestational-age (SGA) babies at increased risk of morbidity more accurately than population centiles, but they have not been validated in obese populations.
Aims: To compare the rates of SGA by population and customised birthweight centiles in babies of women with type 2 diabetes and examine perinatal outcomes in customised SGA infants.
Methods: Data were from a previous retrospective cohort study detailing pregnancy outcomes in 212 women with type 2 diabetes. Customised and population birthweight centiles were calculated; pregnancy details and neonatal outcomes were compared between groups that delivered infants who were SGA (birthweight < 10th customised centile) and appropriate weight for gestational age (AGA) (birthweight 10–90th customised centile).
Results: Fifteen (7%) babies were SGA by population centiles and 32 (15%) by customised centiles. Two babies of Indian women were reclassified from SGA to AGA by customised centiles. Nineteen babies were reclassified from AGA to SGA by customised centiles; of these, 15 (79%) were born to Polynesian women, five (26%) were born less than 32 weeks and two (11%) were stillborn. Customised SGA infants, compared with AGA infants, were more likely to be born preterm (19 (59%) vs 20 (16%), P  < 0.001) and more likely to be stillborn (4 (13%) vs 0 P  = 0.001). After excluding still births, admission to the neonatal unit was also more common (19 of 28 (68%) vs 43 of 127 (34%), P  < 0.001).
Conclusions: In our population more babies were classified as SGA by customised compared with population centiles. These customised SGA babies have high rates of morbidity.     

Unadjusted and customised weight centiles in the identification of growth restriction among stillborn infants

The study aims to compare the utility of unadjusted with customised weight standards in the identification of intrauterine growth restriction (IUGR) among unexplained stillborn infants undergoing postmortem examination. Unadjusted and customised birthweight centiles were determined for 51 unexplained stillborn infants undergoing perinatal autopsy. Unadjusted centiles were calculated from an ultrasonically derived fetal weight standard. Customised centiles were calculated from an online calculator which adjusts the standard to account for important physiological variables. IUGR was defined as moderate or severe according to brain/liver ratios of > 3 and > 5, respectively. The relationship between the weight centiles and abnormal brain/liver weight ratios was explored. Neither unadjusted nor customised standards identify stillborn infants with brain/liver ratios > 3:1. Both unadjusted and customised weight standards identify stillborn infants with brain/liver ratios > 5 equally well with high sensitivity (95%) but low specificities (63% and 66%, respectively). Customising weight standards to account for physiological variables does not identify growth restricted stillborn infants more usefully than an unadjusted fetal weight standard.     

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.     

Birthweights in sickle cell trait pregnancies

Objectives  Available evidence on the effect of sickle cell trait (SCT) on birthweight is conflicting, not gestational age specific, and does not account for maternal and infant factors. The objectives of this study are to determine the contemporary mean birthweight, mean customised birthweight centile, and to analyse the risk of small-for-gestational-age (SGA) and large-for-gestational-age (LGA) babies in SCT pregnancies.
Design  Large retrospective cohort study.
Setting  London hospital.
Population  Singleton pregnancies between 24 and 42 completed weeks delivered between 2000 and 2005 in parturient with body mass index between 18.0 and 35.0 kg/m².
Methods  All qualifying pregnancies were identified on Terra Nova Healthware. Birthweight centiles of these cases were computed with Gardosi customised bulk centile calculator using collected data on maternal height, weight, ethnicity and parity, and the infant's gender, gestational age and birthweight. Birthweight and birthweight centiles of SCT and pregnancies with no haemoglobinopathy (control) were compared. Statistical analysis was performed using Stata version 9.2.
Main outcome measures  Birthweight and birthweight centiles.
Results  Five hundred and five SCT and 16 320 controls were analysed. The mean birthweight of SCT pregnancies was 3223 g, 57 g lower than controls ( P = 0.024). However, its mean birthweight centile was 49.0% similar to that of controls' 47.5% ( P = 0.320). There is an apparent risk of LGA babies in SCT pregnancies, but logistic regression analysis suggests that the odds are related to being an older non-white parturient and a male infant rather than SCT status.
Conclusions  SCT is not a risk factor for SGA or LGA infants.     

The use of customised versus population-based birthweight standards in predicting perinatal mortality

OBJECTIVE: The objective of this study was to critically examine potential artifacts and biases underlying the use of 'customised' standards of birthweight for gestational age (GA). DESIGN: Population-based cohort study. SETTING: Sweden. POPULATION: A total of 782,303 singletons > or =28 weeks of gestation born in 1992-2001 to Nordic mothers with complete data on birthweight; GA; and maternal age, parity, height, and pre-pregnancy weight. METHODS: We compared perinatal mortality in four groups of infants based on the following classification of small for gestational age (SGA): non-SGA based on either population-based or customised standards (the reference group), SGA based on the population-based standard only, SGA based on the customised standard only, and SGA according to both standards. We used graphical methods to compare GA-specific birthweight cutoffs for SGA using the two standards and also used logistic regression to control for differences in GA and maternal pre-pregnancy body mass index (BMI) in the four groups. MAIN OUTCOME MEASURES: Perinatal mortality, including stillbirth and neonatal death. RESULTS: Customisation led to a large artifactual increase in the proportion of SGA infants born preterm. Adjustment for differences in GA and maternal BMI markedly reduced the excess risk among infants classified as SGA by customised standards only. CONCLUSION: The large increase in perinatal mortality risk among infants classified as SGA based on customised standards is largely an artifact due to inclusion of more preterm births.     

Relationship between customised birthweight centiles and neonatal anthropometric features of growth restriction

Objective To determine the relationship between customised birthweight centiles (adjusted for maternal and fetal physiological variables) and neonatal anthropometric features of intrauterine growth restriction (IUGR).
Design Observational study.
Population Two-hundred and seventy women with low risk pregnancies participating in a cohort study of serial ultrasound biometry.
Methods Customised birthweight centiles were calculated following adjustment for maternal weight, height and ethnic origin, gestational age at delivery, birth order, and sex of the infant. Three separate neonatal anthropometric measures were used to define IUGR: subscapular or triceps skinfold thickness  <10th  centile; ponderal index  <25th  centile; and mid-arm circumference to occipito-frontal circumference ratio (MAC/OFC) <−1 standard deviation (SD). Relationship of the centiles to these outcomes was evaluated using likelihood ratios (LR) and kappa statistic. These approaches allowed us to examine the strength of the association: an LR of 5–10 would be expected to generate moderate changes in the pre-test probability of IUGR, whereas a kappa value of 0.2–0.4 would reflect fair agreement between customised birthweight centiles and neonatal anthropometric measures.
Results Customised birthweight centile of 10 or less had the following LR values for the various anthropometric criteria for IUGR: 5.1 (95% CI 3–8.5) for low skinfold thickness; 4.3 (95% CI 2.5–7.1) for low ponderal index; and 3.9 (95% CI 2–6.6) for low MAC/OFC ratio. The kappa values were: 0.4 (95% CI 0.26–0.51) for low skinfold thickness; 0.33 (95% CI 0.21–0.46) for low ponderal index; and 0.13 (95% CI 0–0.26) for low MAC/OFC ratio.
Conclusion In a low risk population, customised birthweight centiles can only be moderately useful in the identification of neonates with low skinfold thickness and low ponderal index.     

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.     

Development of a customised birthweight standard for ethnic Chinese subjects

A model to establish customised birthweight standards for the Chinese population was developed, using data from a cohort of 1564 Chinese women with normal singleton pregnancies. Multiple regression analysis was performed using maternal height, weight, parity, gestation at delivery and fetal sex as independent (predictor) variables. From this, a customised ideal birthweight for each baby can be estimated, and the normality of the actual birthweight can be evaluated according to this, rather than from population standards. The results of this study show that birthweights are strongly influenced by maternal characteristics, confirming conclusions from similar studies in other ethnic populations. The overall mean birthweight at 280 days of gestation was 3252 g, which was smaller than that of the Caucasian population. Birthweight increased with maternal height (5.1 g/cm), maternal booking weight (10.2 g/kg) and gestation at delivery (18.3 g/day from 280 days). Babies from women who had two previous deliveries weighed 145.2 g more than the nulliparous. Male babies were 84.8 g heavier than females. Adjustment using these results produces a customised ideal birthweight for each baby. When compared with population based standards, customised birthweight standards identified significantly fewer small for gestational age (SGA - birthweight below 10th centile, McNemar Chi square = 19.1, p < 0.01) and fewer large for gestational age (LGA - birthweight above 90th centile, McNemar Chi square = 23.7, p < 0.01) cases.     

The relationship between intrauterine growth restriction and preterm delivery: an empirical approach using data from a European case-control study

Objective To test whether being small for gestational age, defined as having a birthweight less than the 10th centile of intrauterine growth references, is a risk factor for preterm delivery for singleton live births.
Design A case-control study.
Setting Maternity hospitals in 16 European countries.
Sample Four thousand and seven hundred preterm infants between 22 and 36 completed weeks of gestation and 6460 control infants between 37 and 40 weeks of gestation.
Methods Newborn babies are identified as being small for gestational age using customised reference standards derived from models of fetal growth. The impact of being small for gestational age on preterm delivery is estimated using logistic regression.
Main outcome measure Spontaneous or induced preterm delivery.
Results Being small for gestational age is significantly associated with preterm birth, although the magnitude of this association differs greatly by type of delivery and gestational age. Over 40% of induced preterm births for reasons other than the premature rupture of membranes are small for gestational age compared with 10.7% of control infants (OR 6.41). For spontaneous or premature rupture of membranes related preterm births, the association is also significant, but weaker (OR 1.51). The relationship between growth restriction and preterm delivery is strongest for preterm births before 34 weeks of gestation.
Conclusions These findings highlight the phenomenon of abnormal fetal growth in all premature infants and, in particular, infants delivered by medical decision for reasons other than premature rupture of membranes. The observed association between being small for gestational age and preterm delivery among spontaneous preterm births merits further attention because the causal mechanisms are not well understood.     

A customised birthweight centile calculator developed for a New Zealand population

BACKGROUND: Traditionally, small for gestational age is defined as birthweight <10th percentile using sex-adjusted centile charts. However, this criterion includes constitutional variation due to maternal height, weight, ethnic group and parity. Aims: To develop customised birthweight centiles for a New Zealand population. METHODS: National Women's Hospital database of births from 1993 to 2000 was used to identify eligible women with singleton pregnancies who had data available on the following: scan result for dating at gestation <24 weeks, maternal height and weight at booking, parity and ethnic origin. Multiple regression was used to determine the coefficients applicable to New Zealand. RESULTS: A total of 4707 pregnancies met the inclusion criteria comprising: European 1688 (36.0%), Maori 419 (8.9%) Samoan 506 (10.7%), Tongan 326 (6.9%), Chinese 751 (16.0%), Indian 214 (4.6%) and other 803 (17.1%). Mean term birthweight for an average nulliparous European woman was 3530 g. Babies of Maori and Indian ethnicity were on average 67 g and 150 g lighter, respectively, than European babies. Samoan, Tongan and Chinese babies were 84 g, 124 g and 101 g heavier, respectively. CONCLUSIONS: There are significant differences in birthweight between European and the other major ethnic groups in New Zealand. They relate to maternal physiological variables, for which coefficients have been derived and incorporated into freely available software that enables improved clinical assessment of fetal and neonatal weight.     

Pregnancy outcome in women presenting with pre-eclampsia at less than 25 weeks gestation

OBJECTIVE: We aimed to (i) assess maternal and perinatal outcomes in pre-eclampsia at < 25(0) weeks; and (ii) determine if any antenatal factors were associated with adverse maternal and perinatal outcomes. DESIGN: A retrospective study. SETTING: Tertiary referral hospital, Auckland, New Zealand. METHODS: Data were extracted from the clinical record and hospital database. The study population involved women admitted with pre-eclampsia at < 25(0) weeks, with a live singleton pregnancy, from 1997 to 2004 and managed expectantly. OUTCOME MEASURES: Maternal morbidity, perinatal death, neurodevelopmental outcome at 18 months, small for gestational age assessed by population and customised birthweight centiles. RESULTS: Gestation at admission was the only antenatal variable associated with adverse perinatal outcome. Of 14 women admitted < 23 weeks, no babies survived, but eight (62%) babies of women admitted in the 24th week (24(0)-24(6)) survived. Neurodevelopmental outcome was assessed in eight of nine survivors; two (25%) had moderate and two (25%) had minor disability. All babies in this cohort had birthweights < 5th customised centile. Only one baby (10%) weighing < 500 g survived. CONCLUSION: Maternal morbidity was high in this expectantly managed cohort. As no babies survived when pre-eclampsia occurred before 23 weeks, induction of labour should be considered. In the 24th week two-thirds of babies survived and 25% had moderate handicap. This information may help clinicians and women in the future to make informed choices about management.     

Should parity be included in customised fetal weight standards for identifying small-for-gestational-age babies? Results from a French multicentre study

Objective  Parity is one of several parameters used to customise fetal growth norms. However, it is uncertain whether the lower birthweight of babies born to primiparous women reflects physiological or pathological variation. Our aim was to assess the impact of adjusting for parity in identification of small-for-gestational-age (SGA) births.
Design  Comparison of two customised definitions of SGA with and without parity.
Setting  Routinely collected data in five tertiary maternity hospitals in France.
Population  A total of 51 126 singleton births without malformations from 1997 to 2002.
Methods  Characteristics of mothers and babies and adverse pregnancy outcomes for SGA and non-SGA births were compared using customised definitions with and without parity.
Main outcome measures  Neonatal morbidity and mortality.
Results  SGA births among primiparas increased from 14.9 to 18.0% when parity was excluded. Overall rates of SGA rose from 14.4 to 15.0%. Newly defined cases of SGA were babies of primiparas. They had higher rates of admission to a neonatal unit and caesarean section than babies reclassified as non-SGA. Perinatal mortality was 9.1‰ (parity included) and 9.7‰ (parity excluded) and did not differ significantly from babies classified as non-SGA by both standards (5.4‰).
Conclusions  Adjustment for parity markedly decreased the proportion of primiparas diagnosed with SGA babies but did not appear to improve the identification of high-risk babies. Removing parity would simplify the customised definition of SGA and would eliminate the need for the assumption that lower birthweight for primiparous women is normal.     

Significance of low birthweight for gestational age among very preterm infants

Objective To estimate the risk of specific adverse neonatal events resulting from the combined effects of prematurity and low birthweight in very preterm infants (delivered at 24–31 weeks of gestation)
Design A cohort study of specific adverse neonatal events in preterm infants born at between 24 and 31 weeks of gestation.
Setting Pavia, Italy.
Population Two hundred and thirty singleton infants with sonographically confirmed gestational age, delivered at 24 to 31 weeks of gestation.
Methods To evaluate the impact of a lower than expected birthweight on selected neonatal events independently of gestational age, we calculated birthweight standard deviation scores (differences between actual birthweight and fitted birthweight divided by fitted standard deviation) for each week of gestation.
Results After adjustment for gestational age and other confounders, there was a significant linear trend relating a decreasing birthweight SDS to an increased likelihood of neonatal death, intraventricular haemorrhage, severe respiratory distress syndrome, and acidosis. Compared with infants with SDS 0 ( 50th centile of birthweight), infants with birthweight SDS < −1 (< 16th centile) had increased odds for neonatal death [odds ratio (OR) 3.7, 95% confidence interval (CI) 1.42–9.6], grade III-IV intraventricular haemorrhage (OR 17.5, 95% CI 4.04–75.9), and neonatal acidosis (OR 3.22, 95% CI 1.41–7.4). The significance of birthweight SDS as a predictor of neonatal outcome, however, was lower than that of gestational age.
Conclusions A lower than expected birthweight affects the likelihood of several adverse neonatal events in very preterm infants. However, a decreasing birthweight SDS affects neonatal outcome less than decreasing gestation does.     

Psychosocial predictors of low birthweight: a prospective study.

OBJECTIVE: To examine the role of psychosocial risk factors for low birthweight. DESIGN: A prospective study. SETTING: Obstetric outpatient clinics of the University Hospital Vrije Universiteit, Amsterdam. PARTICIPANTS: Three hundred and ninety-six nulliparous women. METHODS: Questionnaires on background variables, daily stressors, psychological and mental wellbeing, social support and work factors were completed by the women in the first, second and third trimester of pregnancy. Low birthweight for gestational age was defined at different cut off points: 1. < or = 10th customised birthweight centile (n = 69); 2. < or = 5th customised birthweight centile (n = 54); 3. < 3rd customised birthweight centile (n = 35); and 4. < or = the 10th Dutch birthweight centile (n = 40). Multivariate logistic regression was applied and the results were expressed in odds ratios and their 95% confidence intervals. RESULTS: When the cut off level was defined < or = 5th and < 3rd customised centile, the number of daily stressors in the first trimester was a statistically significant risk factor (OR 1.04, 95% CI 1.01-1.07 and OR 1.04, 95% CI 1.01-1.08). No significant psychosocial risk factors could be identified when low birthweight for gestational age was defined < or = the 10th customised birthweight centile. When low birthweight for gestational age was defined < or = the 10th Dutch birthweight centile, number of hours housekeeping per week in the first trimester (OR 1.59, 95% CI 1.03-2.46), low subjective severity rating of daily stressors in the first trimester (OR 0.41, 95% CI 0.17-0.97) and depressive mood in the first trimester (OR 1.12, 95% CI 1.01-1.24) were statistically significant psychosocial risk factors after controlling for maternal weight and height, number of cigarettes smoked per day and educational level. CONCLUSIONS: In the first trimester of pregnancy maternal psychosocial factors are associated with an increased risk of low birthweight. The specific psychosocial risk factors found were different when the definition of low birthweight was changed. Therefore, in this field of research, we suggest use of the most valid outcome measure for low birthweight, being the customised birthweight centiles.     

Customized birthweight centiles predict SGA pregnancies with perinatal morbidity

OBJECTIVES: To determine the following: (1) the proportion of babies reclassified as small or appropriately grown using customized and population centiles; and (2) the relative risks of perinatal morbidity, including abnormal umbilical Doppler studies, in babies classified as small for gestational age (SGA) and appropriate for gestational age (non-SGA) using the two centile calculations. DESIGN: Cohort study in SGA and general hospital populations. SETTING: National Women's Hospital, Auckland, NZ. POPULATION: A cohort of SGA pregnancies (n= 374) and a general obstetric population (n= 12,879). METHODS: Pregnancy outcomes were compared between 'non-SGA both' (> or =10th% by population and customized centiles) and those who were 'SGA both' (<10th% by population and customized centiles), 'SGA customized only' (SGA by customized but non-SGA by population centiles) and 'SGA population only' (SGA by population but non-SGA by customized centiles). MAIN OUTCOME MEASURES: Maternal and newborn morbidity and perinatal death. RESULTS: In the SGA cohort 271 (72%) babies were 'SGA both', 27 (7%) were 'SGA customized only', 32 (9%) were 'population SGA only' and 44 (12%) were 'non-SGA both'. In the general obstetric population 863 (6.7%) babies were 'SGA both', 445 (3.5%) were 'customized SGA only', 285 (2.2%) were 'population SGA only' and 11,286 (88%) were 'non-SGA both'. Perinatal death and newborn morbidity including nursery admission and long hospital stay were increased and comparable between 'SGA both' and 'customized SGA only' in both study populations. Newborn morbidity was low and comparable between 'population SGA only' and 'non-SGA both'. No perinatal deaths occurred in 'population SGA only' babies. Abnormal Doppler studies were more common in 'SGA both' or 'customized SGA only' but not in 'population SGA only' groups compared with 'non-SGA both'. CONCLUSIONS: Customized birthweight centiles identified small babies at risk of morbidity and mortality. Use of customized centiles is likely to detect more babies at risk of perinatal morbidity and mortality than would be detected by population centiles.     

Birthweight by gestational age and its effect on perinatal mortality in white and in Punjabi births: experience at a district general hospital in West London 1967–1975

Summary. At Hillingdon Hospital in West London two main ethnic groups: 'UK' (i.e., white European) and 'Indian' (i.e. Punjabi) account for the bulk of obstetric work load. Birthweight by gestational age graphs were calculated for some 6000 Indian and 18000 UK infants born between 1967 and 1975 inclusive. A mean weight difference at term favoured UK male babies by 240 g and UK female babies by 230 g. Though the crude perinatal results in the two populations were not significantly different, the perinatal mortality of infants <2500 g in birthweight was lower in the Indian than the UK population, particularly in the 1500–2400 g group. This is attributed to a levelling off in intrauterine growth from 36 to 37 weeks gestation onwards in Indian compared with UK pregnancies, so that they were more mature than UK births of the same weight. However light-for-dates births, defined as birth weights below the 10th centile of weight-for-gestational age on their own ethnic and sex specific standards pose problems, irrespective of ethnic background.     

Customised fetal growth chart: a systematic review.

Customised fetal growth chart is used to individualise fetal weight for gestational age by adjusting for physiological variables known to affect birth weight and growth. Compared with the standard population-based growth chart, the customised growth chart allows for better distinction between normal and abnormal smallness and reduces the false positive and false negative diagnosis of fetal growth restriction. The charts are currently being introduced into clinical practice in the West Midlands as well as in several units around the country. A Medline and systematic review search from 1980 to 2004 was performed in order to collect information and evidence on the use of customised growth chart and its effect on perinatal outcome.     

Epilepsy and pregnancy: effect of antiepileptic drugs and lifestyle on birthweight

Objective To investigate the impact of epilepsy and antiepileptic drugs on length of gestation and anthropometric measures of the newborn.
Design Cohort study based on questionnaires mailed to all pregnant women who attended for prenatal care at our department from August 1989 to January 1997.
Setting Department of Obstetrics and Gynaecology at Aarhus University Hospital, Denmark.
Participants One hundred and ninety-three singleton pregnancies in women with epilepsy were compared with 24,094 singleton pregnancies in women without epilepsy.
Main outcome measures Preterm delivery, small for gestational age, mean gestational age, gestational age-adjusted birthweight, head circumference, and body length.
Results Children of women with epilepsy who smoked had lower gestational age and were at increased risk of preterm delivery (OR 3.4; 95% CI 1.8–6.5), compared with children born by nonepileptic women who smoked. Birthweight adjusted for gestational age was reduced by 102 g (95% CI 40–164) in women with epilepsy, and the risk of delivering a child who was small for gestational age was increased (adjusted OR 1.9, 95% CI 1.3–2.7), compared with women without epilepsy. Newborn babies of women with epilepsy treated by drugs had a reduced adjusted birthweight (208 g, 95% CI 116–300), head circumference (0.4 cm, 95% CI 0.0.0.7), and body length (0.5 cm, 95% CI 0.1–1.0), compared with the newborn infants of women without epilepsy.
Conclusions Women with epilepsy who smoked were at increased risk of preterm delivery compared with healthy smokers. Children of women with drug treated epilepsy had lower birthweight, length, and head circumference than children of women without epilepsy.     

Selection biases invalidate current low birthweight weight-for-gestation standards

Objective To obtain unbiased estimates of the variation of birthweight with gestation in infants born before 32 weeks of gestation.
Setting The former Northern Regional Health Authority.
Design Information on birthweight was collected during a collaborative study of every registered and unregistered birth at 22 to 31 weeks of gestation in the region in 1983 and 1990 to 1991. These birthweights were then related to computer-generated Tyneside norms for all registered births at 28 to 42 weeks of gestation between 1984 and 1991. Some local information was also collected on fetal weight after termination of pregnancy on social grounds at 16 to 21 weeks of gestation.
Results Weight centiles constructed after excluding infants with a gross, externally visible, malformation and those dying before the onset of labour suggest that previously published European standards have overestimated birthweight in infants < 28 weeks of gestation, some low centiles being 30% in error. Female and first-bom infants weighed 4% less than their male and later-born counterparts at all gestations studied. A single correction factor can therefore be used to correct for sex and parity, eliminating the need for separate centile graphs. Twin pregnancy was associated with a 10% reduction in mean birthweight in pregnancies lasting < 37 weeks, and this difference increased progressively in pregnancies lasting longer than this.
Conclusion The small number of low birthweight infants in previous datasets and the selective exclusion of all nonregistered births have made previous second trimester weight-for-gestation norms unreliable.