Young maternal age and infant mortality: the role of low birth weight

In 1980, there were 562,330 babies born in the United States to teenage mothers (19 years of age or younger). The offspring of teenage mothers have long been known to be at increased risk of infant mortality, largely because of their high prevalence of low birth weight (less than 2,500 grams). We used data from the National Infant Mortality Surveillance (NIMS) project to examine the effect of young maternal age and low birth weight on infant mortality among infants born in 1980 to U.S. residents. This analysis was restricted to single-delivery babies who were either black or white, who were born to mothers ages 10-29 years, and who were born in one of 48 States or the District of Columbia. Included were 2,527,813 births and 28,499 deaths (data from Maine and Texas were excluded for technical reasons). Direct standardization was used to calculate the relative risks, adjusted for birth weight, of neonatal mortality (less than 28 days of life) and postneonatal mortality (28 days to less than 1 year of life) by race and maternal age. There was a strong association between young maternal age and high infant mortality and between young maternal age and a high prevalence of low birth weight. Neonatal mortality declined steadily with increasing maternal age. After adjusting for birth weight, the race-specific relative risks for babies born to mothers less than 16 years of age were still elevated from 11 to 40 percent, compared with babies born to mothers 25-29 years of age.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ethnic differences in perinatal mortality--a challenge.

The perinatal mortality rates of mothers who delivered at St. Thomas's Hospital from 1969 to 1976 have been examined. The rate in the West Indian population was significant higher than in the United Kingdom white population. The increased West Indian mortality was confined to infants with a birth weight of more than 2.0 kg and a gestational age of more than 37 weeks. The relative risk of perinatal death for West Indian mothers compared with UK white mothers was 1.4 at birth weights of 2.5 kg to 2.9 kg, rising to 4.3 at 4.0 + kg. West Indian perinatal mortality in term babies of normal birth weight was higher in all maternal age and parity groups except parity 3, but the difference was greatest in women aged 30 or over. The African perinatal mortality rate was not significantly greater than the UK white rate although it followed the West Indian trends. Pre-eclampsia and forceps delivery were associated with a greatly increased perinatal mortality in West Indian babies. The excess West Indian mortality could not be explained completely by differences in the proportions of stillbirths and early neonatal deaths nor by the distribution of births by parity, maternal age, or social class. Possible explanations for the differences in mortality are discussed.     

Prevalence of low birth weight and its determinants in an urban resettlement area of Delhi

Birth weight remains an important factor affecting infant and child mortality. Many factors influence the occurrence of low birth weight (LBW). The present study was conducted to study the prevalence and determinants of LBW in an urban resettlement area of Delhi. A baseline survey was done to enroll all pregnant women in the area. These women were followed up every month till outcome. The prevalence of LBW was 39.1%. Occurrence of LBW was related to age, parity, weight and height of the mother. In multiple logistic regression analysis, mother's weight and parity alone emerged as significant variables. On further analysis, on adjusting for age, parity and birth weight were associated for the 20-35-year age group only. Thus, prevalence of LBW remains high in the urban under privileged of Delhi; maternal age, parity and weight and height are important determinants. Increasing age of first birth to more than 20 years can minimize effect of primi parity.     

Parity specific perinatal mortality. A longitudinal study based on sibships

Perinatal mortality in sibships has been examined using the Medical Birth Registry of Norway. Using linear logistic regression, parity specific perinatal mortality in the period 1967-1981 has been analysed, controlling simultaneously for maternal age, year of birth and survival of earlier births. The risk of a perinatal loss was increased by a factor of up to 6.0 following one earlier perinatal loss, and with three earlier losses the increase was 17.0. The general reduction in mortality between the different five year periods varied according to parity and maternal age. No secular reduction in risk, however, was demonstrated in sibships where the first birth died perinatally; for some subgroups of women the risk actually increased between the first and the second five year period. The effect of maternal age changed with parity, being strong in the first birth order, but of no effect either for the third or the fourth birth orders once the perinatal survival of earlier births was controlled for. This study shows the need to take heterogeneity of risk between women into account in studies of perinatal loss; the overall improvement in perinatal mortality does not apply to every woman. As care improves, perinatal losses become less and less random, demonstrated by increased risks of recurrence.     

Perinatal mortality in relation to birthweight and gestational age: a registry-based comparison of Northern Norway and Murmansk County, Russia

The objective was to explore how perinatal mortality relates to birthweight, gestational age and optimal perinatal survival weight for two Arctic populations employing an existing and a newly established birth registry. A medical birth registry for all births in Murmansk County of North-West Russia became operational on 1st January 2006. Its primary function is to provide useful information for health care officials pertinent to improving perinatal care. The cohort studied consisted of 17,302 births in 2006-07 (Murmansk County) and 16,006 in 2004-06 (Northern Norway). Birthweight probability density functions were analysed, and logistic regression models were employed to calculate gestational-age-specific mortality ratios. The perinatal mortality rate was 10.7/1000 in Murmansk County and 5.7/1000 in Northern Norway. Murmansk County had a higher proportion of preterm deliveries (8.7%) compared to Northern Norway (6.6%). The odds ratio (OR) of risk of mortality (Northern Norway as the reference group) was higher for all gestational ages in Murmansk County, but the largest risk difference occurred among term deliveries (OR 2.45, 95% confidence interval 1.45, 4.14) which hardly changed on adjustment for maternal age, parity and gestation. Proportionately, more babies were born near (± 500 g) the optimal perinatal survival weight in Murmansk County (67.2%) than in Northern Norway (47.6%). The observed perinatal mortality was higher in Murmansk County at all birthweight strata and at gestational ages between weeks 25 and 42, but the adjusted risk difference was most significant for term deliveries.     

深圳市2008年高龄产妇妊娠结局分析

目的:探讨深圳市高龄产妇与不良妊娠结局的关系,为妇幼卫生政策提供依据。方法:对深圳市妇幼信息系统2008年深圳市161362例产妇资料进行分析,采用单因素分析比较不同年龄段产妇基本状况及妊娠结局,采用多因素Logistic分析产妇高龄与早产及低出生体重的关系,分析软件使用SPSS15.0。结果:深圳高龄产妇的比例逐年上升;单因素分析表明,随产妇年龄的增加,初产妇比例下降,孕前超重、肥胖比例增加,剖宫产比例增加;40岁以上产妇分娩婴儿的平均出生体重显著低于30～34岁以及35～39岁产妇,平均孕周显著低于其他年龄组,早产儿、低出生体重儿、小于胎龄儿比例、围产儿死亡率在产妇各年龄段分布呈中间低两头高态势,极早早产儿、极低低出生体重儿比例均以40岁以上产妇比例最高,出生缺陷率随产妇年龄增加而增加。多因素分析显示,控制产妇户籍类型、产次、体质指数、小孩性别后,与20～29岁组相比,35～39岁组和≥40岁组产妇低出生体重儿和早产儿的危险性增加。结论:深圳市大样本研究表明产妇高龄与不良的妊娠结局有关。     

Thinness at birth in a northern industrial town.

OBJECTIVE--To determine whether babies in an area of Britain with unusually high perinatal mortality have different patterns of fetal growth to those born elsewhere in the country. DESIGN--Measurement of body size in newborn babies. SETTING--Burnley (perinatal mortality in 1988 15.9/1000 total births) and Salisbury (perinatal mortality 10.8/1000 total births), England. SUBJECTS--Subjects comprised 1544 babies born in Burnley, Pendle, and Rossendale Health District, and 1025 babies born in Salisbury Health District. MAIN OUTCOME MEASURES--Birthweight, length, head, arm and abdominal circumferences, and placental weight were determined. RESULTS--Compared with babies born in Salisbury, Burnley babies had lower mean birthweight (difference 116 g, 95% confidence interval (CI) 77,154), smaller head circumferences (difference 0.3 cm, 95% CI 0.2, 0.4), and were thinner as measured by arm circumference (difference 0.3 cm, 95% CI 0.3, 0.4), abdominal circumference (difference 0.5 cm, 95% CI 0.4, 0.6) and ponderal index (difference 0.8 kg/m3, 95% CI 0.6, 1.0). The ratio of placental weight to birthweight was higher in Burnley (difference 0.6%, 95% CI 0.4, 0.9). These differences were found in boys and girls and did not depend on differences in duration of gestation or on the different ethnic mix of the two districts. Mothers in Burnley were younger, shorter in stature, had had more children, were of lower social class, and more of them smoked during pregnancy than mothers in Salisbury. These differences did not explain the greater thinness of their babies. CONCLUSIONS--Babies born in Burnley, an area with high perinatal mortality, are thin. The reason is unknown. Poor maternal nutrition is suspected because Burnley babies have a higher ratio of placental weight to birthweight. The greater thinness at birth of Burnley babies could have long term consequences, including higher rates of cardiovascular disease.     

Persistence of lower birth weight in second generation South Asian babies born in the United Kingdom

OBJECTIVE: To assess differences in birth weight between all first and second generation South Asian babies born in Southampton, and trends since 1957. DESIGN: Retrospective, cohort study. SETTING: Birth records for babies born in Southampton from 1957 to 1996 were searched to identify all babies born of South Asian origin (including from the Indian subcontinent, East Africa, and elsewhere). MAIN OUTCOME MEASURES: All information recorded in the birth record about the mother and baby was extracted. RESULTS: 2395 full term (>37 weeks; mean birth weight 3110; 95%CI 3092 to 3129) singleton births were identified. Detailed analysis was restricted to mothers either born in the Indian subcontinent (India, Pakistan, or Bangladesh (1435)) or United Kingdom (283). Mean birth weight and % low birth weight (<2500 g) were 3133 g (95%CI 3108 to 3157) and 7.5%, for first generation babies and 3046 g (2992 to 3099) and 11.7% for second generation babies. There was no trend over time to increased average birth weight in either first or second generation babies. Adjusting for other factors that were statistically significantly related to birth weight (gender, gestational age, mother's age, maternal weight at 15 weeks, parity, and mother's ethnic group) did not alter the trends. CONCLUSIONS: For that group in the UK who derive from the Indian subcontinent, average birth weight is significantly less than the national average. There has not been any increase in the average birth weight over the past 40 years, and the birth weight of babies of women who were born in the UK are no greater. The persistence of lower than desirable birth weight may result long term in higher than average rates of diabetes and heart disease in these groups.     

Children with low birth weight and low gestational age in Oslo, Norway: immigration is not the cause of increasing proportions.

STUDY OBJECTIVE--To determine the influence of children born to immigrant mothers on the total proportions of low birth weight and preterm deliveries in Oslo and to explain the increases in the proportions of children with low birth weight and low gestational age since 1980-1982. DESIGN--This was a cross sectional study based on Norwegian Medical Birth Registry data and information on mothers' country of birth from the Central Bureau of Statistics. SETTING--Oslo, Norway 1968-91. POPULATION--All births in Oslo between 1968 and 1991 (n = 146 133). MAIN RESULTS--The observed increased proportion of children with low birth weight and low gestational age born after 1980-82 is not the result of an increased proportion of children born to immigrant women. Caesarean section rates have increased dramatically and the higher proportions of children with low birth weight and gestational age may be explained by this. CONCLUSION--Wide use of caesarean section probably results in more children of low birth weight and low gestational age as an iatrogenic effect. The trend in the proportion of children with low birth weight and low gestational age is not correlated to perinatal mortality after 1982. Using proportions of low birth weight and gestational age as indicators of a nation's child health status may therefore be misleading in countries with high rates of caesarean section.     

Effect of maternal and infant covariates on sibship correlation in birth weight

Birth weight on 12,644 singleton infants from 6,196 sibships born in Maryland between 1980 and 1984 were used to estimate the effects of nine maternal and infant covariates on the sibship correlation in birth weight. Assuming a homogeneous correlation across all families, the estimated intraclass correlation was 0.4664 (+/- 0.0099). This high sibship correlation makes it possible to predict, with reasonable accuracy, the birth weight of a child given information on previous sibs, as well as covariates on the mother and/or infant pertinent to a given pregnancy. The reduction in variance associated with incorporating information on the nine covariates used here was approximately equal to that obtained by conditioning on a single previous sib. Testing for heterogeneity in correlation among different groups of families showed that a crude measure of parity (first live birth vs. other), time between births, mother's marital status, and maternal age at the birth of the last child significantly influenced the sibship correlation in birth weight.     

江西省农村地区儿童保健指标状况及影响因素分析

目的:了解江西省农村地区儿童保健指标的变化情况,探讨围产儿死亡率及新生儿死亡率的影响因素。方法:利用江西省1999年与2005年的妇幼卫生保健年报表,并对随机抽取的妇幼保健人员进行定性访谈。结果:新生儿死亡率、婴儿后期死亡率、婴儿死亡率、5岁以下儿童死亡率、新生儿破伤风发病率、低出生体重儿发生率、5岁以下儿童中重度低体重患病率均有所下降且有显著性差异(P<0.001):围产儿死亡率、新生儿破伤风病死率变化无统计学意义;0～3岁儿童系统管理率下降且有显著性差异(P<0.001)。1999年与2005年围产儿死亡率和新生儿死亡率的影响因素发生变化。结论:提高医疗质量,改善农村地区孕妇与围生儿在围产期医疗保健的可及性。     

Effect of sex of preceding child on birth interval

The study aim was to examine the effect on birth spacing of a prior female child's birth. The study site was a rural health center under observation by staff from the Dayanand Medical College in Ludhiana, India. The sample included 73 pregnant women who were grouped by the sex of the preceding child. The results showed that the average birth interval was significantly shorter for women with a preceding birth of a female child. The average interval in weeks was 90.73 weeks + or - 54.46 weeks for the 41 women who had a prior girl child compared to 133.68 weeks for the male child. When the female child was at a parity of one the birth interval averaged 73.36 weeks, compared to 137.2 weeks for a prior parity of one male child. At parity of two, the average birth interval was 106.2 for a prior girl child and 144.38 for a prior male child. At a parity of three, the average birth interval was 88.22 weeks for a prior girl child and 96.5 weeks for a prior male child. At a parity of four, the average birth interval was 87.66 weeks for a prior girl child and 46.0 weeks for a prior male child. The significant effect of having a prior girl child was evident only at a parity of one. The intervals at a parity of two and three were shorter for girls but not significantly different. The recommendation was that young women and women with low parity be targeted for family planning in order to lengthen the birth interval, regardless of the desire for sons.     

Determinants of perinatal and infant mortality in Italy.

Determinants of stillbirths, perinatal and infant mortality in Italy have been analyzed using information collected routinely by the Italian Central Institute of Statistics on more than 2,400,000 births and 33,000 infant deaths in the period 1980-1983. Individual records included data on maternal (i.e. age, education, obstetric history) and fetal characteristics (sex, birth weight, gestational week at birth). The Italian stillbirth, perinatal and infant (1st-365th day of life) mortality rates in the period considered were respectively 7.7/1000 births, 16.4/1000 births and 13.5/1000 livebirths. Perinatal and infant mortality was extremely elevated in the very-low-birth-weight category. About 90% of liverbirths weighing less than 1000 g died within the first year of life, but this fell to about 45% in babies weighing 1000-1499 g. Among other factors, stillbirth, perinatal and infant mortality rates were elevated among males, born to older women and in higher birth rank and multiple pregnancies. These findings persisted, although less markedly, after adjustment for weight. Mortality rates were about 50-70% higher in less educated women. This finding was not markedly changed after adjustment for birth weight and maternal age, suggesting that socio-economic factors are per se important determinants of perinatal and infant mortality in Italy.     

A prospective study of psychosocial job strain and birth outcomes.

We conducted a prospective study in Alabama to examine the relation between job strain during pregnancy and birth outcomes. We hypothesized that maternal jobs high in demands and low in control would lead to lower birth weight in offspring. The sample consisted of 480 black and white women, 20 to 34 years of age receiving early prenatal care. Adjusting for standard covariates, women with high strain jobs had babies with birth weights 190 gm lower than those born to mothers in low strain jobs or unemployed (95% CI = 48 gm, 333 gm). Black women experienced a greater effect from job strain than white women.     

The effect of parental age, birth order and other variables on early childhood mortality: a Caribbean example.

The 4275 births to women of native ancestry that took place on the island of St Barthélemy, French West Indies between 1878 and 1970 were analyzed according to the sex of the child, the year of birth, maternal age, maternal parity, paternal age and the number of children the father already had to determine the effects of these variables on rates of perinatal death, death before age 1 and death before age 5. The year of birth, the number of children the father already had, and maternal parity influenced death before age 1 and death before age 5. The sex of the child also influenced the probability of dying in the first year of life but not the first 5 yr of life when the other variables were controlled. Perinatal deaths were influenced only by the sex of the child, but even this effect disappeared when the other variables were controlled.     

Out-of-hospital births, U.S., 1978: birth weight and Apgar scores as measures of outcome

An examination of 1978 natality data for the United States disclosed that low birth weight was less common among 30,819 infants born out of hospital than among 3,294,101 infants born in hospital in that year. When controls were applied for birth attendant, infants' race, and mothers' education, age, nativity, and parity, the data revealed that white, well-educated women between 25 and 39 years of age, who were having their second babies and were attended by midwives out of hospital, were at least risk of bearing low birth weight infants. The incidence rate of low birth weight babies was lower for midwife-attended births in every category examined. For college-educated white women, for example, the incidence rate was 2.0 percent among those attended by midwives, 4.6 percent among those giving birth in hospital, and 3.6 percent among those whose out-of-hospital deliveries were attended by physicians. Apgar scores for babies born both in and out of hospital were also studied but, because of inconsistent reporting, were given less attention. Excellent (9-10) Apgar scores were more common among babies born out of hospital than among those born in hospital (63 percent compared with 49 percent), particularly for out-of-hospital births attended by physicians. At least with respect to birth weight and Apgar scores, the claim that out-of-hospital births are inherently more dangerous than hospital births receives no support from these data. The findings also suggest the need for further refinement of vital statistics categories to permit the analysis of distinctions between births attended by certified nurse-midwives and those attended by lay midwives, as well as differences between births at home and those in alternative birth centers.     

Factors associated with birth weight in Sweden: the study of men born in 1913.

STUDY OBJECTIVE: To analyse factors associated with birth weight and to evaluate the validity of obstetrical data. DESIGN: Obstetrical data were retrieved for singleton men born in 1913 and living in Gothenburg, Sweden in 1963. Information on birth weight, maternal age, marital status, parity, social class, proteinuria, gestational age, and place of birth (home or hospital) was obtained from these birth records. SETTING: Sweden. PARTICIPANTS: Fifty year old men living in Gothenburg, Sweden, in 1963. MAIN RESULTS: Obstetrical records were obtained for 524 men (65%). Place of birth, gestational age, maternal age, parity, proteinuria, and marital status were all significantly correlated to birth weight. In multivariate analyses, place of birth, gestational age, parity, and proteinuria influenced birth weight. There was a substantial difference in mean birth weight between hospital deliveries (3352 g) and home deliveries (3817 g), which could be explained only partly by sociodemographic variables. Birth weight increased with parity and gestational age in home delivered babies as well as those delivered in a hospital. CONCLUSIONS: The validity of obstetrical records from 1913 was good. The place of birth (home or hospital) is strongly associated with birth weight and may be a confounding factor in studies of the implications of birth weight for future risk of disease or death.     

Effect of morbidity during pregnancy on birth weight in a rural guatemalan population

The high prevalence of low birth weight (≤ 2.5 Kg) babies is a major public health problem in many poor communities. Studies in humans suggest that malnutrition during pregnancy is an important factor in accounting for this problem, but almost no information is available about the effect of common maternal diseases during pregnancy. This paper reports the effects of maternal morbidity during pregnancy on birth weight in four rural villages of Guatemala. Maternal morbidity, assessed through fortnightly interviews during pregnancy, showed a consistent inverse association with birth weight (r = —0.149, n = 344, p<0.01). In each village, the proportion of low birth weight babies born to mothers who were ill more than 10 percent of their pregnancy was consistently higher than the proportion of babies born to mothers who were sick 10 percent (or less) of their pregnancy (p<0.01). The relationship between the proportion of time ill and birth weight was basically unchanged (r = —0.182, n = 334, p<0.01) after controlling for maternal height, head circumference, parity, gestational age, socioeconomic status, home energy intake, energy supplementation during pregnancy and number of days surveyed during pregnancy. Moreover, a similar association was found in consecutive pregnancies of the same mother (r = —0.197, n = 50, p = 0.16). It was concluded that maternal morbidity during pregnancy caused a decrease in birth weight.

In addition, an inverse association was observed between the proportion of time ill during pregnancy and home energy intake (r = —0.254, n = 334, p<0.01). However, the amount of birth weight variance explained by morbidity during pregnancy did not decrease significantly after statistically controlling for home energy intake. Therefore, either the diet measurement is imprecise or the decrease in energy intake observed during illness was not an important mechanism.     

A comparative review of Asian and British-born maternity patients in Bradford, 1974-8.

The perinatal mortality rate for Asian babies born in Bradford during the five years 1974-8 was persistently higher than for babies born to United Kingdom mothers. A comparative review of 18 924 British indigenous and 6443 Asian immigrant maternity patients delivered in Bradford from 1974-8 demonstrated several differences between the two ethnic groups. Factors operating in favour of Asian women were fewer teenage mothers, lower rates of illegitimacy, and fewer smokers. On the other hand, a greater number of factors presented increased risks to Asian patients-more women aged over 35, lower social class, higher parity, shorter pregnancy intervals, previous perinatal deaths, shorter duration of antenatal care, anaemia, shorter gestations, more babies born without professional help, and more low-birthweight babies. Local health education programmes are now concentrating on encouraging expectant mothers to attend early and regularly for antenatal care, to breast-feed their babies, and to increase the interval between pregnancies to at least one year.     

Race, family income, and low birth weight.

The relations among race, family income, and low birth weight were examined using information obtained from the National Longitudinal Survey of Youth, which conducted yearly interviews with a nationally representative sample of young women identified in the late 1970s. Data were available for these women and their offspring from 1979 through 1988. Maternal education, maternal age, age/parity risk, marital status, and smoking during pregnancy served as covariates in cross-sectional and longitudinal analyses. The risk of low birth weight among births to black women and white women who were poor was at similarly high levels regardless of whether poverty was determined prior to study entrance or during the study period. Longitudinal analyses showed an exceptionally large increase in risk of low birth weight among children born to women whose prior pregnancy ended in a low-birth-weight infant. These two findings emphasize the importance of factors antecedent to the pregnancy in the genesis of low birth weight.