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PubMed2002

Low birthweight children: coping in school?

AIM: To describe and compare school performance and IQ at 11 y of age in a population of 130 children weighing less than 2000 g at birth without any major handicaps (low birthweight) and a random control sample of 131 children born at term weighing over 3000 g (normal birthweight); and to evaluate the relative strength of parental factors versus child birthweight in predicting IQ. METHODS: The mothers and teachers completed validated questionnaires addressing school performance and the child's IQ was evaluated by WISC-R, prorated. In addition, socioeconomic status was investigated using different questionnaires. RESULTS: According to maternal reports, twice as many low birthweight children had school problems and three times as many of these children were referred to the School Psychological Service. Mean prorated IQ was 5 points lower in the low birthweight group. No statistically significant difference was found for mean IQ between the groups with birthweights of less than 1500 g vs 1500-2000 g. In a multivariate linear regression analysis, parental factors accounted for 13% of the variance in child IQ compared with only 3% accounted for by child birthweight. CONCLUSION: Low birthweight significantly increases the risk of school problems.

Adaptation, Psychological↗
PubMed1999

Effect of breastfeeding and morbidity on the development of low birthweight term babies in Brazil.

Low birthweight (LBW) occurs in 17% of births in developing countries and many of them are full term. The subsequent development of LBW term infants is poorer than higher birthweight children and more likely to be affected by poor social circumstances. We investigated the effects of morbidity and breastfeeding on the development of these LBW term infants. Two parallel cohorts (n = 131 + 131) of LBW term (1500-2499 g) and higher birthweight (3000-3499 g) infants were recruited from six maternity centers in northeast Brazil. The longitudinal prevalence of morbidity and the frequency of breastfeeding over the first 6 mo of life were assessed. The infants' development was assessed on the Bayley Scales at 6 and 12 mo, and we previously reported that the low birthweight group had lower scores than the higher birthweight group. Hospitalizations in the first 6 mo were negatively associated with 6-mo and 12-mo Bayley scores in both groups. Among LBW infants, but not higher birthweight infants, there were significant associations between the prevalence of diarrhea and mental and motor development at 6 mo and mental development at 12 mo. Breastfeeding frequency in the first 4 wk of life was positively associated with mental development in both birthweight groups at 6 mo but not at 12 mo. Breastfeeding beyond 4 wk was not associated with the children's development. We conclude that low birthweight infants are especially vulnerable to the effects of diarrhea, and the greater frequency and differential effect of diarrhea partly explains their poorer development.

Birth Weight↗
PubMed1987

Cigarettes, alcohol and marijuana: varying associations with birthweight.

The relations of cigarette smoking, alcohol drinking and marijuana use during pregnancy to birthweight were examined in two prospectively studied pregnancy cohorts (Phases I and II). After analytic adjustment in ordinary least squares regressions for other factors that influence birthweight, cigarette smoking during at least half the pregnancy was associated with a significant decrease in mean birthweight (159 grams in Phase I, 202 grams in Phase II). In Phase II only, beer drinking was associated with a significant decrement of 8.4 grams in estimated birthweight per ounce of absolute alcohol per month. Neither wine nor liquor drinking in the Phase II data nor any of the three beverages in the Phase I data was associated with significant decrements in predicted birthweight. Furthermore, with one exception (drinking once a week in Phase II only), alcohol drinking, defined as the number of occasions per month on which any alcoholic beverage was consumed, was not associated with a change in birthweight. Regarding marijuana use, the data are not consistent between the two phases. In the Phase I data, no coherent trend in association with birthweight was observed. In the Phase II data, marijuana use 2-3 times per week, 4-6 times per week and daily was associated with increasing decrements in estimated birthweight: 127 g, 143 g and 230 g respectively. The inconsistent findings for alcohol drinking and marijuana use between phases stand in marked contrast to the consistent findings for cigarette smoking.

Adult↗
PubMed1999

Can accurate data on birthweight be obtained from health interview surveys?

BACKGROUND: Because hospital records rarely exist for a representative sample of the population in developing countries, researchers frequently rely on birthweight data from surveys. Yet, the quality of these data has rarely been evaluated. This study explores the accuracy of birthweight information in six demographic and health surveys in Latin America conducted in the early 1990s: two in Guatemala, and one each in Bolivia, Costa Rica, El Salvador and Peru. METHODS: The quality of the birthweight reports is assessed by examining the plausibility of estimates of the proportion of newborns reported to have been weighed and estimates derived from the numerical weights, by characteristics of the delivery and maternal education. RESULTS: The estimates suggest that a substantial proportion of women whose newborns were probably never weighed report a birthweight. For all of the surveys, with the possible exception of Costa Rica, the average birthweights appear to be too high, and the estimates of the prevalence of low birthweight too low. In addition, the data reveal anomalous patterns, such as higher birthweights for home as compared with hospital deliveries. CONCLUSIONS: These findings suggest that estimates of low birthweight derived from surveys in developing countries are likely to portray an overly optimistic picture of children's and women's health status. More information about the underlying source of these data are needed not only to provide additional insight into the degree of error characterizing existing estimates, but also to improve data collection strategies in future health interview surveys.

Birth Weight↗
PubMed2000

Social determinants of birthweight and length of gestation in Estonia during the transition to democracy.

BACKGROUND: To investigate social variation in birthweight and length of gestation in Estonia in the period of transition to a democracy and market economy. METHODS: All live births resulting from singleton pregnancies reported to the Estonian Medical Birth Registry in 1992-1997 (n = 84, 629) were studied with respect to social variation in birthweight and preterm delivery (<37 weeks gestation). The results were adjusted for maternal age, parity, education, nationality, marital status, smoking in pregnancy, sex of the infant (and gestational age). RESULTS: Between 1992 and 1997, mean birthweight increased from 3,465g to 3,497g (P < 0.001) and the preterm rate fell from 5.8% to 5.1% (P = 0.001). Maternal education, marital status and nationality were all independently related to the mean birthweight and the risk of preterm birth. The mean difference in birthweight between children of mothers with basic and university education was 87 g (95% CI : 74-100). Children born to mothers of non-Estonian compared to Estonian nationality were on average 77 g lighter (95% CI: 70-84). While the effect of nationality and marital status on birthweight was relatively stable during the study period, differences in birth outcome by maternal education became stronger. CONCLUSIONS: The mean birthweight increased and the preterm rate decreased in Estonia as a whole during the transition. However, the improvements were not shared equally by all social groups. An increase in variation in birthweight by maternal education was particularly notable.

Adolescent↗
PubMed2001

On the importance--and the unimportance--of birthweight.

Birthweight is one of the most accessible and most misunderstood variables in epidemiology. A baby's weight at birth is strongly associated with mortality risk during the first year and, to a lesser degree, with developmental problems in childhood and the risk of various diseases in adulthood. Epidemiological analyses often regard birthweight as on the causal pathway to these health outcomes. Under this assumption of causality, birthweight is used to explain variations in infant mortality and later morbidity, and is also used as an intermediate health endpoint in itself. Evidence presented here suggests the link between birthweight and health outcomes may not be causal. Methods of analysis that assume causality are unreliable at best, and biased at worst. The category of 'low birthweight' in particular is uninformative and seldom justified. The main utility of the birthweight distribution is to provide an estimate of the proportion of small preterm births in a population (although even this requires special analytical methods). While the ordinary approaches to birthweight are not well grounded, the links between birthweight and a range of health outcomes may nonetheless reflect the workings of biological mechanisms with implications for human health.

Birth Weight↗
PubMed2004

Poverty, birthweight, and infant weight gain in Hertfordshire, 1923-1939.

OBJECTIVE: To investigate the association between poverty, birthweight, and infant weight gain in Hertfordshire, 1923-1939. DESIGN: Cohort study based on the Hertfordshire Health Visitors' Register (HHVR). SETTING: The population of Hertfordshire, and a sub-sample of five Hertfordshire towns-Hoddesdon, Berkhampstead, Hertford, Hitchin, and Bishops Stortford-extracted from the HHVR. SUBJECTS: Some 71 201 live birth entries in the HHVR and a sample of 13,649 live birth entries for the five towns. MEASURE OF POVERTY: Rateable value of birth addresses reflecting market and rental value of housing. MAIN OUTCOME MEASURES: Birthweight, and infant weight gain (z score of weight at one year minus z score of birthweight). RESULTS: In Hertfordshire as a whole there was a reduction in mean birthweight from 7.7 pounds (lbs) in 1923 to 7.4 lbs in 1939. Over the same time period there was an increase in mean infant weight gain, although with a degree of variation within the trend. In the sample of five towns there was no association between rateable value and birthweight, but a significant association between rateable value and both weight at one year, and weight gain during the first year of life. CONCLUSION: In Hertfordshire average birthweight declined, whereas weight gain during the first year of life tended to increase, at a time when, nationally, calorific intake and per capita consumption of a range of nutritional ingredients was rising. Poverty, as measured by rateable value, did not correlate with birthweight but was associated with weight gain during the first year of life. These findings suggest that nutritional poverty had a more significant influence on post-natal weight gain than it did on birthweight.

Birth Weight↗
PubMed2004

The association of maternal growth and socio-economic measures with infant birthweight in four ethnic groups.

BACKGROUND: Both maternal socio-economic status (SES) and growth measures are themselves interrelated and are also related to infant birthweight. The objective of this study is to compare the relative importance of such maternal measures as determinants of birthweight of female infants-the prospective mothers of the next generation. METHODS: The study base was derived from a population-based multiethnic intergenerational cohort: the Washington State Intergenerational Cohort. Infants of mothers from four ethnic groups were included: non-Hispanic Whites, African Americans, Native Americans, and Hispanics. We generated simple, partial, and multiple correlation coefficients to investigate the association between birthweight and the maternal growth and SES measures. RESULTS: While there were slight differences among the ethnic groups, generally each of three maternal pre-conceptional growth measures-birthweight, stature, and pre-pregnant weight-was a stronger predictor of female infant birthweight than were each of the five maternal SES factors-age, parity, marital status, educational attainment, and prenatal care onset. After accounting for the proportion of variation in birthweight explained by the maternal growth measures and maternal smoking, the addition of the five SES variables added relatively little to the prediction of infant birthweight. The maximal multiple correlation coefficients (R2) yield values ranging from 9.5% to 12.8%. CONCLUSIONS: A mother's growth before pregnancy is a stronger predictor of infant birthweight than is her current socio-economic circumstance. Since the mother's growth must have been influenced by the socio-economic circumstances of her family of upbringing, this further highlights the intergenerational contribution on a woman's reproductive success.

Adult↗
PubMed2006

Differential parental weight and height contributions to offspring birthweight and weight gain in infancy.

BACKGROUND: Parental weight and height correlate with offspring birthweight and weight gain, suggesting genetic and environmental influences on fetal growth. The differential contributions of the mother's and father's height and weight to birthweight, or weight gain in infancy, remain unclear and were examined using data from the UK Millennium Cohort Study. METHODS: We calculated z-scores for birthweight and conditional weight gain to age 9 months (weight gain adjusted for birthweight) for 6811 term white singleton infants living with natural parents, using the British 1990 growth reference. We also calculated parental height and weight z-scores. The effects of parental size on birthweight and weight gain were analysed using multivariable regression, with a novel reparameterization to test for differences in effect size between mother and father. RESULTS: Maternal weight had a far greater influence than paternal weight on birthweight [coefficient for the difference between parents (95% CI): 0.15 (0.100.20)], while parental height contributions were similar [0.03 (-0.02 to 0.07)]. Weights and heights of mothers and fathers contributed equally to infant weight gain [difference coefficients -0.03 (-0.09 to 0.02) and 0.02 (-0.03 to 0.07), respectively]. CONCLUSIONS: The influences of parental height and weight on birthweight and infant weight gain are similar for the two parents, with the exception of the influence of weight on birthweight where the mother is much more influential than the father. Parental size associations with infant growth result from a complex combination of genetic and environmental influences. This novel reparameterization of parental anthropometry is applicable to other studies examining parental influences on offspring size and growth across the life course.

Birth Weight↗
PubMed2004

The relation of insulin, leptin and IGF-1 to birthweight in offspring of women with type 1 diabetes.

OBJECTIVE: Maternal diabetes is associated with excess foetal growth. We have assessed the influence of maternal diabetes on hormones associated with foetal growth and the relationship of these hormones to birthweight. DESIGN: Case-control study. PATIENTS: Singleton offspring of mothers with type 1 diabetes (ODM, n = 140) and control mothers (Control, n = 49). MEASUREMENTS: Birthweight, cord blood insulin, proinsulin, 32-33 split proinsulin, leptin, IGF-1, IGFBP-3, cortisol. RESULTS: Maternal diabetes was associated with higher birthweight (ODM 3.80 +/- 0.69 kg; Control; 3.56 +/- 0.52 kg, P = 0.02) and marked increases in insulin (median [interquartile range]: ODM 110 [60-217] pmol/l; Control 22 [15-37] pmol/l; P < 0.0001) and leptin (ODM 32 [15-60] ng/ml; Control 9 [4-17] ng/ml; P < 0.0001) but no absolute difference in IGF-1 (ODM 7.9 [6.2-9.8] nmol/l, Control 7.5 [6.2-9.8] nmol/l, P = 0.24) or its principle binding protein IGFBP-3 (ODM 1.63 +/- 0.38 micro g/ml, Control 1.63 +/- 0.28 micro g/ml; P = 0.12). Individually, insulin, insulin propeptides, leptin, IGF-1 and IGFBP-3 were significantly (P < 0.05) correlated with birthweight (in ODM and Control). IGF-1 and leptin were positively related to birthweight independently of each other and insulin in both ODM and Control. By contrast, insulin showed independent relationships to birthweight in ODM (P < 0.0001) but not in Control (P = 0.4). CONCLUSIONS: Maternal diabetes is associated with marked elevation of insulin and leptin in cord blood of their offspring. Hormonal correlates of birthweight differ between ODM and Control with an independent relationship of insulin to birthweight observed only in ODM.

Adult↗
PubMed2006

Health-related quality of life among 3--4-year-old children born with very low birthweight.

AIM: This paper reports a study comparing health-related quality of life at 3-4 years of age among children born with very low birthweight (<or=1500 g) to a group of non-very low birthweight controls, and to examine biological, environmental, demographic and health factors associated with quality of life of children born with very low birthweight. BACKGROUND: Advances in modern medicine have increased the survival of infants with very low birthweight, but its impact on quality of life of children during preschool years has been less studied. METHODS: The study sample included 118 children born with very low birthweight and 170 non-very low birthweight controls in Taiwan. Primary caregivers of the study children completed structured questionnaires during the period November 2002 to April 2003. Health-related quality of life was measured using the Mandarin version of the TZO-AZL Preschool Children Quality of Life instrument. This tool has four dimensions: physical, emotional, cognitive and social functions. Higher scores indicate better quality of life. FINDINGS: Children born with very low birthweight had statistically significantly lower mean quality of life scores in all the four dimensions compared with controls. Among the former, those who had current physical health problems scored lower in all dimensions of quality of life. Primary caregivers with higher educational levels and increased ages of the children were associated with improved scores in the emotional and social functions. Birth gestational age was negatively associated with cognitive function. Length of stay in the neonatal intensive care unit was negatively associated with scores for the social function aspect of quality of life. CONCLUSION: Regular monitoring of the quality of life among very low birthweight children is needed. Nurses need to assess the child's current health state, birth gestational age, and the primary caregiver's educational level in order to identify those who are at risk for low quality of life and intervene early.

Case-Control Studies↗
PubMed2004

Impact of pregnancy-induced hypertension on birthweight by gestational age.

Few studies to date have examined the effect of severe pre-eclampsia, pre-eclampsia, and gestational hypertension on birthweight according to gestational age. We conducted a population-based retrospective cohort study of 16,936 pregnant women in Suzhou, China. Analysis of variance and multivariable linear regression were performed to compare the mean birthweights of babies born to mothers with gestational hypertension, pre-eclampsia, and severe pre-eclampsia with birthweights of infants born to mothers with normal blood pressure at each week of gestation. The differences in mean birthweight between women with severe pre-eclampsia and women with normal blood pressure ranged between -467.7 g and 189.1 g. The birthweights were statistically significantly lower in women with severe pre-eclampsia than in women with normal blood pressure for gestational age categories < or = 35 and 36 weeks. However, after adjustment for confounding variables, the birthweights were not statistically significantly different in women with severe pre-eclampsia when compared with women with normal blood pressure even at < or = 35 and 36 weeks. The differences in mean birthweight between women with pre-eclampsia and women with normal blood pressure ranged between -132.2 g and 174.6 g. These differences were not statistically significant, before or after adjusting for confounding variables. There were no differences in mean birthweight between women with gestational hypertension and women with normal blood pressure. Further analysis suggested that pre-eclampsia and gestational hypertension were associated with increased rates of both small-for-gestational-age and large-for-gestational-age infants. The majority of the babies born to mothers with different types of pregnancy-induced hypertension were appropriate-for-gestational-age or even large-for-gestational-age. In this Chinese population, most babies born to mothers with severe pre-eclampsia or pre-eclampsia and gestational hypertension had similar fetal growth to those born to normotensive mothers.

Adult↗
PubMed2005

An investigation of folate-related genetic factors in the determination of birthweight.

Recent evidence suggests that maternal folate status in early gestation is a significant determinant of infant birthweight. Folate metabolism is known to be controlled by genetic factors, with a number of polymorphic variations in folate metabolising genes identified, several of which have well-documented functional effects. The current study investigated whether folate-related polymorphic variation, in association with low maternal folate status, influences birthweight. Red blood cell (RBC) folate analysis and genotyping of five polymorphisms in folate-related genes [Methylenetetrahydrofolate reductase (MTHFR) 677C>T; MTHFR 1298A>C; cystathionine-beta-synthase (CbetaS) 844ins68bp; serine hydroxymethyltransferase (SHMT) 1420C>T; reduced folate carrier-1 (RFC-1) 80G>A] were undertaken in mothers and infants from 998 pregnancies. These data were analysed in relation to infant birthweight, adjusted for gender and gestational age (z-score). Low maternal RBC folate status was associated with reduced infant birthweight. None of the genetic variants studied showed an independent association with infant birthweight. However, two genetic variants were shown to have a significant effect on birthweight when found in association with low maternal RBC folate status. When individuals with variant genotypes and mothers with folate in the lowest quintile were compared with wild-type individuals and mothers with folate in the highest quintile, the following differences in mean birthweight (z-score) were observed; maternal MTHFR 677C>T (-0.56 [95% CI -1.00, -0.12]P=0.01) and infant CbetaS 844ins68bp (-0.71 [95% CI -1.97, -0.07]P=0.03). The findings of this study suggest that folate-related genetic polymorphisms do not directly influence infant birthweight. However, when placed on a background of deficient maternal nutritional status, they may detrimentally affect fetal growth.

Birth Weight↗
PubMed1980

A longitudinal study of very low-birthweight infants. IV: An overview of performance at eight years of age.

A cohort of 169 very low-birthweight infants (800 to 1500g) was followed prospectively to the age of eight years. Information on 159 of the children was available at that age, and for a further five to the age of six years. A comparison group of 67 normal-birthweight children was also followed, but only 43 of these children were seen at the age of eight years. Eight of the very low-birthweight (VLBW) children were attending special schools and 156 attended normal schools: placement of the remaining five was unknown. Of the VLBW children who were adequately assessed, 15.9 per cent were either not reading or were retarded by more than 18 months. Mean VLBW full-scale IQ was 88.8, compared with 98.8 for the normal-birthweight group. A subgroup of 10 VLBW children with birthweights under 1000g had lower mean scores on all three WISC-R scales compared with those with birthweights between 1000 and 1500g. Of the adequately assessed VLBW children, 3.7 per cent had epilepsy, 3.7 per cent had significant sensorineural deafness and 2.4 per cent suffered from cerebral palsy. One or more visual defects were detected in 31.4 per cent of the children, though in only 3.8 per cent was the defect serious. At eight years, growth dimensions for the VLBW children were below the 10th percentile for 11.0 per cent in weight, 16.1 per cent in height and 15.0 per cent in head circumference. Degrees of handicap in the VLBW children were profound in 5.1 per cent, severe in 10.8 per cent and significant in 40.5 per cent: handicap was minimal or absent in the remaining 43.6 per cent. For the normal-birthweight group the percentages were 2.3, 0, 25.6 and 72.1 respectively. The VLBW children with minimal or no handicap were considered to have a satisfactory outcome. This was significantly correlated with the following: gestation over 30 weeks; birthweight over 1199g; no major apnoeic attacks; lowest postnatal weight before six days; return to birth weight before 21 days; peak serum bilirubin not exceeding 255 mumol/litre; and parental social-class between 2 and 5 on the seven-point Congalton Scale.

Child↗
PubMed1995

The effect of social deprivation on birthweight, excluding physiological and pathological effects.

OBJECTIVE: To study the effect of social deprivation on birthweight, excluding the effect of known physiological factors and exploring the effect of possible pathological factors. DESIGN: Retrospective analysis of computerised obstetric database. SETTING: Two teaching hospitals and an associated district general hospital which provided a defined catchment area in the East Midlands. SUBJECTS: The final analysis included 7493 women with complete datasets and gestations of between 259 and 300 days at delivery, dated by ultrasound scan. MAIN OUTCOME MEASURES: Smoking habit, alcohol consumption, weight gain during pregnancy, systolic and diastolic blood pressures at booking, bleeding during pregnancy and Jarman score; also, the effect of these variables on birthweight, adjusted for the effects of physiological factors using the individualised birthweight ratio. RESULTS: Smoking during pregnancy reduced birthweight but the effect is not linear, becoming less marked as the number of cigarettes smoked increases. Alcohol intake, diastolic and systolic blood pressures at the booking visit and vaginal bleeding during early pregnancy were not significantly related to birthweight. Pregnancy weight gain was significantly positively related to birthweight especially in the normal weight range (60-99 kg). A multivariate analysis including physiological and pathological factors found increasing Jarman score to be negatively related to birthweight. CONCLUSIONS: In this central British population social deprivation is correlated negatively with birthweight: the most socially deprived mothers have the smallest babies. This association cannot be explained in terms of physiological differences in the population nor in a higher prevalence of known pathological factors.

Alcohol Drinking↗
PubMed1996

Smoking during pregnancy: the dose dependence of birthweight deficits.

OBJECTIVE: To assess whether a simple urine based estimate of relative daily nicotine intake could predict smoking related birthweight deficits more accurately than self-reported cigarette consumption. DESIGN: Active smokers were identified by a simple qualitative colorimetric urine test procedure and their relative nicotine intakes assessed by determining the ratios of the urinary concentrations of nicotine plus its metabolites to creatinine using automated colorimetric methods. SETTING: A large teaching hospital. PARTICIPANTS: Three thousand and thirty-eight mothers from whom smoking histories had been elicited and who gave birth to live singleton babies after 28 weeks of gestation. MAIN OUTCOME MEASURES: Birthweights (adjusted for maternal weight, maternal age, baby's sex, parity and length of gestation), maternal weight gains during pregnancy and placental weights. RESULTS: The adjusted birthweight deficits of babies born to proven active smokers averaged 226 g (95% confidence interval 194 g to 258 g), but dose dependent effects were only apparent when nicotine intake was based on urinary nicotine metabolites/creatinine ratios. Among the smokers, adjusted birthweights fell linearly with increasing nicotine intakes but gave a predicted mean birthweight for nonsmokers that was 102 g (95% CI 50 g to 154 g) lighter than that actually found (P < 0.0001). Maternal weight gains during pregnancy were substantially reduced in smokers and correlated more closely with urinary nicotine metabolite excretions than with reported daily cigarette consumptions. Placental weights were unaffected by smoking. CONCLUSION: There was a closer dose-effect relationship between birthweight deficits and urinary nicotine metabolites/creatinine ratios than with self-reported daily cigarette consumptions. The influence of nicotine exposure on birthweight appears to be biphasic, with one mechanism operating at very low levels of tobacco smoke intake and the other causing seemingly linearly related effects over the whole range of nicotine intakes of active smokers. These findings support recent evidence that passive smoking can cause substantial birthweight deficits.

Adult↗
PubMed2000

A population study of birthweight and the risk of caesarean section: Scotland 1980-1996.

OBJECTIVES: 1. To describe the relation between birthweight and risk of emergency caesarean section at term; 2. to determine whether the relation between birthweight and caesarean section differed between male and female babies; and 3. to determine what proportion of the increased rates of caesarean section could be related to greater birthweights. DESIGN: Retrospective population study. SETTING: Data collected from Scottish Morbidity Record 1980 to 1996. POPULATION: All first singleton deliveries by emergency caesarean section and non-elective vaginal birth of live babies at 40 weeks of gestation (n = 120,854). MAIN OUTCOME MEASURE: Delivery by emergency caesarean section. RESULTS: There was a U-shaped relation between birthweight and the risk of caesarean section, with the lowest risk associated with weights in the range 3,000-3,500 g. Overall, male, were more likely to be delivered by caesarean section (relative risk = 1.2, 95% CI 1.2-1.3). The association between male sex and increased risk of caesarean section persisted after adjusting for birthweight, but only males weighing < 4,000 g were at increased risk of caesarean section compared with similarly sized females. Between 1980 and 1996, there were linear increases in the rate of caesarean section (from 7.1% to 10.7%, r2 = 0.8, P < 0.001) and median birthweight (from 3,360 g in 1980 to 3,420 g in 1996, r2 = 0.8, P < 0.001). The population attributable fraction of caesarean sections related to year of delivery 1981-1996 was not significantly altered by adjusting for birthweight (22.3% vs 21.6%). CONCLUSIONS: There is no evidence to suggest that increasing birthweights have contributed to increasing rates of caesarean section in Scotland between 1980 and 1996 among singleton first births non-electively delivered at 40 weeks of gestation.

Birth Weight↗
PubMed2001

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.

Adult↗