Trends In Birth Weight Research Articles

Childhood growth and age at menarche.

To study the influence of birthweight, and weight and height at age seven years, on menarcheal age in a national sample of 1471 girls in England, Scotland and Wales. We studied 1471 girls included in the MRC National Survey of Health and Development. During medical examinations carried out by school doctors in this cohort, born in the first week of March 1946, the mothers of girls were asked whether their daughters had started to menstruate, and if so, the month and year when this happened. Anthropometric measurements at birth and at age seven years were also obtained. Girls who were heavier at age seven years had menarche at an earlier age. The average age at menarche of those in the highest fifth of the distribution of weight at seven years was 7.3 months less than that of those in the lowest fifth of the distribution. In contrast, girls who were heavier at birth had menarche at a later age. The average age at menarche of those in the highest fifth of the birthweight distribution was 2.2 months more than those in the lowest fifth. These opposing trends of birthweight and weight at seven years on age at menarche were observed across the distribution of each variable, and exerted statistically significant (P < 0.001) independent effects in a multivariate model. These observations are consistent with the hypothesis that menarcheal age is linked to programmed patterns of gonadotrophin release established in utero, when the fetal hypothalamus is imprinted, and is subsequently modified by weight gain in childhood.

Restructuring and women's reproductive health: Implications for low birthweight in New York city

Women's health is influenced not only by behavior and culture, but also by the social, economic and political contexts in which women live. We examine the changing context of women's reproductive health in New York City through an analysis of spatial and temporal trends in low birthweight during the late 1970s and 1980s. Using cartographic and statistical methods, the impacts of political and economic restructuring on women's lives and the linkages with changing patterns of women's reproductive health are addressed. The results show that in the city's low status neighborhoods, increases in low birthweight were related to the decline in women's ability to find paid employment, their decreased utilization of prenatal care, and an increased share of households headed by women. The shifting geographical patterns of reproductive health reflect, in part, women's heightened responsibilities in an era of shrinking resources.

Did preterm deliveries continue to decrease in France in the 1980s?

To study the trends in gestational age and birthweight in France, we compared data from three surveys that were based on representative samples of births in 10 French regions and were conducted in 1972, 1981 and 1988-89. Only single livebirths were considered in the analysis. The rate of preterm births decreased from 7.9% in 1972 to 5.8% in 1981 and 4.0% in 1988-89. The corresponding rates of children with a birthweight below 2500 g were 5.4, 4.3 and 4.7%. The mean birthweight of preterm babies born in 1988-89 was lower than the mean birthweight of those born in 1972 and 1981. The reduction in preterm births cannot be attributed to the improved accuracy of gestational age determination, but the general use of ultrasound may have played a major role in the apparent reduction of the mean birthweight of preterm babies.

Trends in an obstetric patient population: An eighteen-year study

Objective: Our goal was to evaluate various trends including gestational age, birth weight, and mode of delivery in an inner-city obstetric patient population delivered at a tertiary medical center.Study Design: We used an 18-year computerized perinatal database collected prospectively since 1975 in an inner-city tertiary medical center. More than 63,500 deliveries from 1975 through 1992 were evaluated. Trends in gestational age, birth weight, and mode of delivery were investigated with Cox-Stuart, regression, and other trend analysis methods.Results: The number of deliveries increased from 2682 in 1975 to 4740 in 1991, an increase of 77%. The median maternal age has increased from 20 years in 1975 to 23 years in 1992 (p < 0.001). Overall, the mean gestational age has declined monotonically from 39.2 ± 2.84 weeks in 1975 to 38.3 ± 3.17 weeks in 1992 (p = 0.057). While the median and lower percentiles of birth weight for singleton births have declined, the 75th and higher percentiles of birth weight have increased during 18 years. Overall, the proportion of preterm births (< 37 completed weeks gestational age) has increased from 3.3% in 1975 to 7.8% in 1991 (p < 0.001). During this period the proportion of low-birth-weight infants (< 2,500 gm) increased significantly from 12.7% to 17.3% (p < 0.001). The proportion of cesarean section deliveries for private patients has declined from 37% in 1975 to 25% in 1992 (p = 0.025), while this proportion has increased monotonically for staff patients from 10% to 17% during this period (p < 0.001).Conclusions: Considering the large size of the database and diverse background of the study population, we believe that these trends can provide a realistic characterization of an obstetric patient population for a large inner-city urban population.

National trends in birth weight: implications for future adult disease

Birth weight is a powerful predictor of infant survival and is associated with morbidity, childhood growth, and adult height. Recently it has been argued that intrauterine conditions, represented by birth weight, have long term effects on adult conditions such as ischaemic heart disease and non-insulin dependent diabetes.1 thus national trends in this health indicator are of great interest. In Scotland birth weight is reported on Scottish Maternity Records (SMR2) and collated by the Scottish Health Service Common Services Agency. The agency provided information on birth weights of liveborn infants since 1975. For England and Wales, routinely collected data on live births were obtained from the Office of Population Censuses and Surveys since 1983, when records were considered to be complete.2 The table shows an increasing percentage of heavier birth weights; regression of …

Genetic evaluation of birth and weaning weight of Gudali and two-breed synthetic Wakwa beef cattle populations under selection in Cameroon: genetic and phenotypic trends

AbstractBreeding programmes for Wakwa and Ngaundere Gudali cattle breeds were initiated in Wakwa (Cameroon) in 1952 and 1965, respectively, to improve growth performance of the indigenous breeds. Animals were selected on 240-day weaning weight (WWT). Data analysed covered the period 1971 through 1985 and consisted of 2211 calf birth weight (BWT) and 1409 WWT records on Gudali and 1196 BWT and 763 WWT records on Wakwa. Selection responses in BWT and WWT were estimated as regressions of average sire estimated transmitting abilities (ETAs) and average dam estimated breeding values (EBVs) on year of calving. ETAs and EBVs were predicted using best linear unbiased prediction procedures. Estimated annual changes in sire ETAs for WWT were 0·67 (s.e. 0·17) and 1·69 (s.e. 1·13) kg/year for Gudali and Wakwa, respectively. Corresponding trends in dam EBVs were –0·03 (s.e. 0·03) and –0·24 (s.e. 0·19) kg/year. Estimated correlated trends in BWT among Gudali and Wakwa sires were 0·09 (s.e. 0·05) and –0·14 (s.e. 0·04) kg/year, respectively. Corresponding correlated trends in BWT associated with dam selection were essentially zero, being –0·001 (s.e. 0·001) and –0·01 (s.e. 0·01) kg/year. Environmental trends were negative for all traits except Gudali WWT. Phenotypic trends were all positive, except that of Wakwa BWT. Overall, selection on WWT yielded moderate selection reponse despite substantial infrastructural constraints in the breeding programme. Trends in sire ETAs and dam EBVs for WWT jointly accounted for estimated genetic gains of 8·60 kg in Gudali and 20·4 kg in Wakwa over the study period. Overall correlated response in BWT during the study period was significant (P &lt; 0·001) and negative for Wakwa. It was positive but not significant for Gudali.

Analysis of the trends of mean birth weight at an obstetric facility in Osaka during the past 30 years (1962-1991)

Annual trends of mean birth weight (MBW) at an obstetric facility in the city of Osaka were examined, based on the data in the delivery records for 30 years from January 1962 through December 1991. MBW at this facility had been decreasing during the years of 1975-1985, after being adjusted for parity (primipara/multipara) and the infants' sex. In addition, annual trends of the rate of intrauterine growth and mean gestational period, which are considered to be the two major processes to governing birth weight, were retarded or shortened during almost the same time. Among some possible factors with causal impacts on birth weight, the advance in maternal age, the lowered parity, and the increase in premature delivery may explain these findings. Additionally, it was suggested that the change of socio-economical environment, including the lifestyle of women, may have did not agree with the decreasing trends of MBW.

Why infant very low birthweight rates have failed to decline in the United States vital statistics.

Very low birthweight (VLBW) rates, i.e. births of < 1500 g, have been long established as the major determinant of outcome for infants. Nevertheless, despite much medical, political and social effort, these rates have not declined during the past 40 years in the US Vital Statistics. To explore the causes of this disturbing finding, trends in low birthweight distribution at a community hospital and the Vital Statistics data were investigated. The weights of livebirths and foetal deaths (27,944 births) at a community hospital during three 5-year periods, 1973-1987, were examined for trends in low birthweight (LBW) distribution, and they were contrasted with the US Vital Statistics. For white infants weighing 500-999 g the livebirth rates declined from 3.7 per 1000 births in period one to 1.1 per 1000 in period three (70.2%); for white infants 1000-1499 g, livebirths declined from 4.2 to 3.2 per 1000. Hospital white livebirths < 2500 g declined 18.7% from the first to the third period. Among black livebirths the LBW rate also declined from 126.4 per 1000 in period one to 85.4 per 1000 in the third period. Foetal deaths declined from 8.2 per 1000 births to 6.2 per 1000 in period three, a 24.4% decline. However, foetal deaths < 500 g increased 411%, from 3.6% of the total foetal deaths in period one to 18.4% in the third period. Increasing registration of births in the US may have hidden a marked improvement in the VLBW problem. More complete registration of births and changes in the perception of viability appear responsible for the artefact.

Association between maternal-fetal HLA-DR relationships and fetal growth.

To determine whether maternal-fetal human leukocyte antigen (HLA) antigenic relationships are associated with differential fetal growth in weight. A cohort of 659 primigravid women were enrolled in this study in the prepartum period and their neonates were subsequently examined. Anthropometric, maternal cigarette smoking behavior, health, pregnancy, and delivery data were collected; serogenetic typing was conducted on maternal and cord bloods to determine maternal and neonatal HLA antigenic phenotypes. Women and their neonates were assigned to one of the four different types of maternal-fetal relationships existing at each of the HLA-A, B, DR, and DQ loci. Birthweights were treated quantitatively and qualitatively (neonates classified as growth-retarded or normal). After controlling for other factors influencing birthweight (e.g., smoking, maternal body size), significantly lower birthweight trends (P < .01) were found when neonates expressed a single HLA-DR antigen and their mothers expressed a second HLA-DR antigen that was foreign (allogeneic) to their neonate. Our findings supports the hypothesis that lack of maternal immune exposure to fetal HLA antigens is associated with a slowing of fetal growth. However, in this situation slowed fetal growth is most likely to occur when the fetus is potentially exposed to maternal HLA-DR alloantigens. We believe this sheds new light on immunologic events at the maternal-fetal interface influencing fetal growth. We present one possible explanation to account for this finding.

A birthweight-for-gestation standard based on 4737 twins born in Sweden between 1983 and 1985.

To construct a birthweight-for-gestation chart based on a population-based material of twins born during a restricted period of time. Nearly all live-born twins born in Sweden between 1983 and 1985, 4737 all told, were included. Excluded from the analysis were 4.7% of the twins that were not on record at the Medical Birth Registry, 1.8% that died before or during birth, and 8.8% that were without a recorded date of birth or only had information on gestational duration estimated from the first day of the last menstrual period. The standard deviation in birthweight was considerable in most gestational weeks; the range (+/- 2 SD) was 1000-3400 g even if exclusively twins (pregnancies) with estimated date of birth from ultrasound examination early in the second trimester were included. Intra-pair discordance increased with gestational duration, especially for unlike-sexed twins, to reach over 400 g at term. On average, boys weighed 92 g more than girls and twins to multiparae weighed 250 g more than twins to primiparae. Maternal age affected birthweight for twins to primiparae, but not to multiparae. Although the problems with secular trends in birthweight were avoided by using a population-based material during a restricted time period, and only twin pregnancies dated with ultrasound were included, the standard deviation in most gestational weeks was still considerable, reflecting the multiplicity of factors involved in determining the birthweight of twins.

Selection for postweaning growth in inbred Hereford cattle: the Fort Keogh, Montana line 1 example.

Demographic characteristics and genetic trends in birth weight and pre- and postweaning ADG were examined in a population of Hereford cattle (Line 1). Line 1 was founded largely from two paternal half-sib sires and has been selected for postweaning growth. There were pedigree records on 951 members of the base population that predated 1935, when data collection began. Numbers of records analyzed using mixed-model methodology were 4,716 birth weight, 4,427 preweaning ADG, and 3,579 postweaning ADG. Birth weight and preweaning ADG were considered to have direct and maternal genetic components. Inbreeding accumulated rapidly from 1935 to 1960 and more slowly (.22%/yr) thereafter. Any reduction in additive genetic variance due to inbreeding and selection may have been offset by a concurrent reduction in generation interval that was observed as time progressed. Expected selection differential for 365-d weight, averaged over sexes, was 31.2 kg per generation. For birth weight, annual genetic trends in direct and maternal effects were 42 +/- 3 g and 15 +/- 3 g, respectively. Annual direct and maternal genetic trends for preweaning ADG were .70 +/- .06 g/d and .63 +/- .06 g/d, respectively. Direct response in postweaning ADG was linear and equal to 5.3 +/- .6 g.d-1.yr-1. As a result, estimated breeding values of birth weight, 200-d weight, and 365-d weight increased by 3.2 kg, 14.5 kg, and 62.4 kg, respectively, from 1935 to 1989. Selection within Line 1 was effective in increasing genetic potential for growth over 13 generations. No selection plateau was observed in any of the traits examined.

Secular trend in birthweight in an industrial hospital in India

Measurement of birthweight is an indicator of community health. The mean birthweight (MBW) of babies born in 1963, 1983 and 1986 were measured in 2254, 3550 and 3368 babies, respectively. Mean (SD) birthweight was found to be 2652 (553) g in 1963, 2724 (502) g in 1983 and 2726 (478) g in 1986. There was a rise in MBW (72 g) between 1963 and 1983 and a reduction in the percentage incidence of low birthweight from 34.29% to 26.06%. A change in birthweight distribution (was also seen, except in extreme weight groups. The improvement in birthweight is statistically significant (p less than 0.001). A trend for increase has been noticed in birthweights, and the mean birthweight values are the same as the national average.

The poor at birth: Birth weights and infant mortality at Philadelphia's almshouse hospital, 1848–1873

Birth weights and infant mortality in Philadelphia from 1848 to 1873 are analyzed using almshouse hospital case records. The mean birth weight was 7.48 pounds for live infants and compares favorably with mid-20th century standards; only 10% were below the critical level of 2500 grams. The absolute risk of fetal and first-day mortality, holding birth weight constant, is considerably higher than in modern data. There is no evidence of a time trend in birth weight, with the important exception of a sharp drop from 1866 to 1870. A mother's length of stay in the almshouse increased the weight of her infant. The poorhouse, despite much criticism, had some ameliorative impact.

Birth weights in three Norwegian cities, 1860-1984. Secular trends and influencing factors.

Data from birth records from three maternity hospitals in Norway have been used to study the trend in birth weight in this country from 1860-1984. The investigation is based on a sample of 200-300 records taken at random from 2 to 5 years around every 10th year, from each of the three maternity hospitals--amounting to a total sample of 9152 women. Besides describing the trend in birth weight, I have analysed the different factors influencing birth weight--using multivariate linear regression methods. The results show that the mean birth weight has changed remarkably little throughout this period of 120 years. The total increase has only been just below 200 g. From Montreal, Ward and Ward (1984) have reported a decrease in mean birth weight of about 430 g during the second half of the last century. The Norwegian data indicates a simultaneous fall in mean birth weight of about 70 g. This fall is, however, found mainly among unmarried women. Thus, the great decline in birth weight which is found in Montreal, is not apparent in our material from Norway, despite the fact that Oslo was industrialized at approximately the same time as Montreal. Of the various independent variables used in the multiple regression analyses, only the following variables appear to be of any importance: the year when the birth took place, the mother's menarcheal age, her marital status, the sex of the child and the parity number. In this material, I have found a linearly increasing birth weight from birth number 2 up to at least parity 8, and a larger increase from parity 1 to 2. The birth weight shows a significant increase in the case of married women as opposed to unmarried. This effect is most marked before 1900, indicating that the social conditions gradually became less unequal after the turn of the century. The birth weights have a decreasing tendency with higher ages of menarche. This tendency is constant throughout the whole period of time. Boys appear to be about 112 g heavier than girls, this difference being largely the same throughout the investigated period.

Uses of available record systems in epidemiologic studies of reproductive toxicology

The uses of available record systems in epidemiologic studies of reproductive toxicology are described with reference to New York State. The available record systems (and relevant reproductive end points) described include: a newborn screening program for metabolic diseases and hemoglobinopathies (relevant to point mutations); chromosome registries and prenatal cytogenetics (for chromosome anomalies); live birth certificates (for birth defects, birthweight, sex ratio, etc); fetal death certificates (for spontaneous fetal deaths); and a statewide cancer registry (for childhood cancers and transplacental carcinogenesis). The uses and limitations of these record systems are discussed, along with examples of their use in descriptive and analytic epidemiologic studies. Descriptive studies outlined include investigations of temporal and geographic trends in birth defects, birth weight, and fetal deaths, with reference to environmental questions (eg, Love Canal, nuclear power plants). Analytic studies described concern parental occupation in relation to specific birth defects (neural tube defects and Down syndrome) and maternal use of contraceptive drugs.

Uses of Available Record Systems in Epidemiologic Studies of Reproductive Toxicology

The uses of available record systems in epidemiologic studies of reproductive toxicology are described with reference to New York State. The available record systems (and relevant reproductive end points) described include: a newborn screening program I-or metabolic diseases and hemoglobinopathies (relevant to point mutations); chromosome registries and prenatal cytogeneties (for chromosome anomalies); live birth certificates (for birth defects, birthweight, sex ratio, etc); fetal death certificates (for spontaneous fetal deaths); and a statewide cancer registry (for childhood cancers and transplacental carcinogenesis). The uses and limitations of these record systems are discussed, along with examples of their use in descriptive and analytic epidemiologic studies. Descriptive studies outlined include investigations at temporal and geographic trends in birth defects, birth weight, and fetal deaths, with reference to environmental questions (eg. Love Canal, nuclear power plants). Analytic studies described concern parental occupation in relation to specific birth defects (neural tube defects and Down syndrome) and maternal use or contraceptive drugs.

PERINATAL OUTCOME IN WESTERN AUSTRALIA, 1968 TO 1975.; 2. SOCIAL AND BIOLOGICAL DETERMINANTS

Trends in perinatal mortality and low birthweight (percentage of livebirths under 2500 g) were analysed in relation to certain social and biological variables. Mothers at high risk of adverse perinatal outcome in terms of perinatal mortality and low birthweight were found to be very young and grand multiparous mothers, old primiparas, unmarried mothers, those with multiple pregnancies and mothers born in Asia.

An analysis of birth weight by gestational age of infants born in England and Wales, 1967 to 1971.

SummaryFrom a sample of 271,519 births occurring in England and Wales from 1967 to 1971 tables have been prepared describing the relationship of birth weight to gestational age, subdivided by the sex of the infant and parity of the mother. The sample was composed of single babies born live in National Health Service (NHS) hospitals at gestational ages of 28 to 44 weeks and they comprised approximately 8.5 per cent of all such births occurring in NHS hospitals during the study period. No secular trend in birth weight was observed. The distribution of birth weights at a given gestational age was normal above 36 weeks but skewed or bi‐modal in preterm infants. The non‐normal distribution of preterm infants could be described accurately in terms of a mixture of two normal distributions with different mean values but the same standard deviation. The population with the higher mean birth weight comprised approximately one‐third of the observations each week between 28 and 34 weeks but was only 0.79 per cent of all births. The mean birth weight varied between 3.10 and 3.37 kg. equivalent to that of term infants of 38 to 39 weeks' gestation. The sex ratio was similar to that of term infants. The sex ratio (the number of single male infants born alive for every 100 female infants) of the population with the lower mean birth weight rose with increasing prematurity and was 127.9 between 28 and 34 weeks. It is concluded that the population of infants with the higher mean birth weight is composed mainly of pregnancies in which the length of gestation was mistaken. The error in gestational age is not a multiple of months but is continuously distributed. These pregnancies form a small fraction of all births but an important fraction of preterm births.Tables of mean birth weight (±1SD), prepared after correction for the nonnormal distribution of preterm birth weights, gave results which were similar to those reported earlier for infants born in Aberdeen. Male infants were heavier than females and infants of multiparae heavier than infants of primiparae at most gestational ages. Centile tables have been prepared for male and female infants which may be useful to those who wish to monitor the birth weights of infants born in England and Wales.

Letter: Familial trends in low birth weight.

Letter: Familial trends in low birth weight.

Four factors influencing birth weight.

The birth weight of newborn infants is usually studied as a concomitant variable to prematurity or infant mortality and less frequently as the variable of primary interest. This investigation concentrates on the relationship of infant birth weight to four other variables. The combined effect of birth order and mother's age on birth weight is analysed in a large sample of births. The influence of maternal age on the birth weight is investigated for each birth order group and, conversely, the influence of birth order is studied at different maternal ages. Both secular and seasonal trends in mean birth weight, which in general are neglected in the literature, are included here.