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.     

低出生体重与产前检查质量的回顾性分析

目的 探讨新生儿低出生体重(LBW)(出生体重＜2500 g)发生率与产前检查质量的关系.方法 采用Kessner's评定方法,对2008年1月至2009年12月在西安交通大学医学院第一附属医院产科产前检查的2964例单胎活产孕妇中,进行《产前检查问卷》调查.剔除缺项≥5项的问卷,共计回收有效问卷2928份,回收率为98.79％.对符合纳入标准的2928例单胎活产儿孕妇的产前检查质量进行评价.按照产前检查质量标准,将其分为充分组(n=1262)、居中组(n=1502)和不足组(n=164).采取回顾性分析方法于产后(2～7)d,依照《孕产妇产前检查手册》或门诊及住院病历记录3组孕妇的一般情况及其产前检查、孕期患病和分娩等情况.采用非条件logistic逐步回归分析法分析与LBW发生的相关危险因素及其与产前检查质量的关系(本研究遵循的程序符合本院人体试验委员会所制定的伦理学标准,得到该委员会批准,征得受试对象知情同意并与之签署临床研究知情同意书).3组孕妇孕前体重指数(BMI)、本次妊娠胎数比较,差异无统计学意义(P＞0.05).结果 LBW儿发生率在充分组、居中组和不足组分别为3.49％(44/1262),5.26％(79/1502)和19.51％ (32/164).产前检查不足组LBW儿发生率最高,与其他两组比较,差异有统计学意义(P＜0.01).LBW儿发生的相关危险因素包括:①孕妇年龄;②婚姻状况;③是否有妊娠合并症;④分娩地点;⑤孕期体重增加;⑥分娩孕周等,与产前检查质量密切相关(r=0.83,0.69,0.85,-0.68,-0.71,-0.74;P＜0.05).LBW儿发生与产次无相关性(r=0.26,P＞0.05).本组LBW儿与正常体重儿(≥2500 g)母亲的产前检查质量、年龄、婚姻状况、产次、是否有妊娠合并症、分娩地点、孕期体重增加、分娩孕周等比较,差异有统计学意义(x2=96.05,58.84,21.41,52.38,38.10,33.44,66.32,258.42;P＜0.05).与正常体重儿比较,LBW儿母亲孕期平均接受产前检查次数较少[(7.6±3.1)次vs.(5.4±2.9)次;t=9.16,P＜0.01];产前检查充分组较居中组LBW儿发生率低(OR=0.51,95％CI:0.35～0.72).调整孕妇年龄、孕期体重增加、妊娠并发症、产前检查医院类别及分娩孕周后,产前检查次数较少,仍是LBW儿发生的危险因素(OR=4.56,95％CI:3.02～6.84).结论 采用Kessner's评定方法评估产前检查质量相对客观准确,产前检查次数较少,是LBW儿发生的独立危险因素.     

Analyzing sibship correlations in birth weight using large sibships from Norway

Data from the Medical Birth Registry of Norway were used to estimate sibship correlations in large sibships (each with ≥5 infants among singleton live births surviving the first year of life), while adjusting for covariates such as infant gender, gestational age, maternal age, parity, and time since last pregnancy. This sample of 12,356 full sibs in 2,462 sibships born in Norway between 1968 and 1989 was selected to maximize the information on parity, and a robust approach to estimating both regression coefficients and the sibship correlation using generalized estimating equations (GEE) was employed. In concordance with previous studies, these data showed a high overall correlation in birth weight among full sibs (0.48 ± 0.01), but this sibship correlation was influenced by parity. In particular, the correlation between the firstborn infant and a subsequent infant was slightly lower than between two subsequent sibs (0.44 ± 0.01 vs. 0.50 ± 0.01, respectively). The effect of time between pregnancies was statistically significant, but its predicted impact was modest over the period in which most of these large families were completed. While these data cannot discriminate whether factors influencing birth weight are maternal or fetal in nature, this analysis does illustrate how robust statistical models can be used to estimate sibship correlations while adjusting for covariates in family studies. Genet. Epidemiol. 14:423–433,1997. © 1997 Wiley-Liss, Inc.     

Prenatal care utilization: its measurement and relationship to pregnancy outcome

This study proposes a redesigned measure of prenatal care utilization based on modifications made to a preexisting index of the adequacy of such care. Six prenatal care utilization groups were delineated: intensive, adequate, intermediate, inadequate, no-care, and missing/unknown. Using 430,349 cases from South Carolina and North Carolina vital records from 1978 to 1982 (live birth-infant death cohort files for white resident mothers), this proposed prenatal care utilization measure was examined by maternal sociomedical risk characteristics (age-parity, marital status, education, complications of pregnancy, and previous pregnancy terminations) and by pregnancy outcomes (birth weight, gestational age, and birth weight- and gestational age-specific neonatal mortality). The intensive prenatal care group had relatively more pregnancy complications but also the most preferred pregnancy outcomes. Appreciable differences in birth weight and gestational age distributions were observed among the prenatal care categories within maternal risk status groups. Increased utilization of prenatal care was associated with higher mean birth weight and gestational age. However, after controlling for maternal risk status, an appreciable variation in birth weight- and gestational age-specific neonatal mortality was not apparent across prenatal care groups.     

Structural factors associated with birth complications in adolescent fertility

The purpose of this study is to examine a set of demographic, economic, familial and health-related factors for their possible significance in differentiating birth complications among a sample of adolescents and their babies in London, Ontario in 1984-86 (N = 260). Variables such as age, marital status, religion, family social class, economic situation, family composition and interaction, prenatal care and smoking behaviour were related to pregnancy and birth complication outcome. For the adolescent mothers, only certain aspects of family social class differentiated those experiencing complications. Several familial factors were associated with the occurrence of infant complications based on the bivariate analyses, but only the work status of the teenager continued to display a significant relationship with infant complications when other factors were controlled through multivariate techniques. In a circumstance in which young pregnant women receive a high degree of personal and medical attention, there appears to be little in the way of structural variables to distinguish complicated birth outcome for either the adolescent mother or her child.     

Impact of Prenatal Care on Infant Survival in Bangladesh

Despite improvements in public health in recent decades, levels of infant and child mortality remain unacceptably high, particularly in developing countries where primary healthcare services including prenatal care services are not universally available. Using information on 7,001 childbirths in five years preceding the 2004 Bangladesh Demographic and Health Survey, this study examined the relationship between receiving prenatal care during pregnancy and infant mortality using multivariate survival analysis. The results are presented in hazard ratios (HR) with 95% confidence intervals (95% CI). Results indicate that children of mothers who did not receive prenatal care during pregnancy were more than twice as likely to die during infancy as children whose mothers received prenatal care during pregnancy (HR=2.40, 95% CI: 1.74, 3.31) independent of child's sex, delivery assistance, birth order; mother's age at child birth, nutritional status, education level; household living conditions, and other factors. Children born to older mothers living in households without safe drinking water were at an increased risk. The study concludes that prenatal care is strongly negatively associated with infant mortality in Bangladesh independent of other risk factors. The results suggest that improving prenatal care services at the community level is key to improving child survival in Bangladesh. Informed consent : This study is based on an analysis of existing survey data with all identifier information removed. The survey acquired informed consent from mothers of the children included in this study before asking any questions and before obtaining anthropometric measurements.     

Causal pathways to infant mortality: linking social variables to infant mortality through intermediate variables

Using a conceptual model that integrates social and biomedical models of causation, this paper delineates the pathways through which social factors ultimately influence infant mortality in the African-American community. Two social factors, maternal education and marital status, are shown to influence the risk of infant death through the following intermediate variables: bio-demographic (maternal age, birth order, birth interval and outcome of last pregnancy), health care (prenatal care utilization) and proximate infant health status at birth (preterm delivery and low birth weight). While the impact of maternal education is largely explained by the intermediate variables, marital status remains a significant, albeit a weak, predictor net of all other variables.     

妊娠期高血压疾病与妊娠结局的相关性

目的:分析妊娠期高血压疾病发病的高危因素以及孕期保健与并发症之间、治疗方案选择与妊娠结局的关系,探讨降低妊娠期高血压疾病的发生率、减少并发症的措施,从而改善母婴结局。方法:回顾性分析我院2004年7月~2006年6月妊娠期高血压疾病患者587例,分析其高危因素、孕期产检情况与并发症发生的比例,妊高征治疗方案选择与妊娠结局的关系。结果:妊娠期高血压疾病高危因素多为肥胖、高龄、精神紧张、双胎、营养差者;并发症的发生率与产检次数成反比,产检越正规、次数越多,并发症发生机会越少,正规产检与不正规产检及从不产检者并发症发生率分别为22.82%、37.41%、63.38%,三者比较P<0.01,差异有显著性;妊娠期高血压疾病实施规范治疗方案与否与早产、低出生体重儿、新生儿窒息、早期新生儿死亡、子痫、心衰、胎盘早剥,差异有显著性。结论:大力宣传孕产期保健知识,加强流动人口管理,提倡正规产检,严格执行妊高征处理规范及三级转诊制度,可减少妊娠期高血压疾病及其并发症,改善母婴结局。     

The epidemiology of sudden infant death in upstate New York: II: birth characteristics.

This study describes the epidemiology of sudden infant death syndrome (SIDS) among infants born during 1974 to upstate New York residents. Birth certificate characteristics for 184 SIDS cases are compared with those of 417 infants dying from other causes in the same age range, 7-365 days. The results confirm the following as infant risk factors: fall or winter birth, low birthweight for gestational age, twin birth, and live birth order three or more. Maternal risk factors include: age under 20, abnormal uterine bleeding during pregnancy, late initiation of prenatal care, less than 12 years of education and single marital status. The increased risk for mothers who first gave birth in their teens and for second-born twins has not been previously reported. The evidence that SIDS babies are small for gestational age, that twins, especially the second born, and babies whose mothers experienced abnormal uterine bleeding during pregnancy are all at increased risk of SIDS suggests that perinatal stress leading to hypoxia is one of the components that determine the risk of SIDS.     

Birth outcomes of prostituting adolescents.

In 1989, researchers at the University of Washington, Division of Adolescent Medicine, described the multifactorial risks of pregnancy for adolescents engaged in prostitution activities. Factors identified as placing this population at particular risk were transience, substance abuse, violence, sexually transmitted diseases, inadequate (or no) medical care, and poor nutrition. The relationship between such risks in the pregnant adolescent and poor birth outcome has been widely demonstrated. In this follow-up study, we describe the birth outcomes of 54 of the original sample of 61 prostituting adolescents who delivered infants between November 1987 and November 1989 in Seattle, Washington. The data were collected by retrospective chart review. Maternal factors evaluated were 1) age 2) ethnic group 3) substance abuse history 4) number of prenatal visits 5) maternal complications and 6) parity. The infant inpatient charts were reviewed for the following characteristics: 1) birth weight 2) occipitofrontal head circumference 3) length 4) Apgar scores and 5) neonatal complications. Results indicated high rates of maternal and infant complications with respect to: preterm birth (22%), precipitous delivery (15%), pregnancy-induced hypertension (16%), positive toxicology screens (28%), meconium staining (30%), infant hypertonicity (30%), and small for gestational age infants (14.5%).     

Effects of social and psychosocial factors on risk of preterm birth in black women

Our objective was to examine how social and psychosocial factors may influence the risk of preterm birth. The design of the study was a hybrid retrospective and prospective cohort. African-American women residing in Baltimore, Maryland, were enrolled prenatally if they received care at one of three Johns Hopkins Medical Institution prenatal clinics (n=384) or enrolled post-partum if they delivered at Johns Hopkins Medical Institution with late, none or intermittent prenatal care (N=459). Preterm birth was defined as less than 37 weeks completed gestation. Interview data were collected on 832 enrolled women delivering singletons between March 2001 and July 2004. The preterm birth rate was 16.4%. In both unadjusted and adjusted models, exposure to racism over a woman's lifetime had no effect on risk of preterm birth in our sample. However, we found evidence of a three-way interaction between reported lifetime experiences of racism, depressive symptoms during pregnancy and stress during pregnancy on preterm birth risk. Racism scores above the median (more racism) were associated with an increased risk of preterm birth in three subgroups with the effect moderated by depressive symptoms and stress. Social and psychosocial factors may operate in a complex manner related to risk of preterm birth.     

Using mixture models with linear predictors to identify incorrect gestational age in state birth records

Background: Birthweight distributions for early last-menstrual-period-based gestational ages are bimodal, and some birthweights in the right-side distribution are implausible for the specified gestational age. Mixture models can be used to identify births in the right-side distribution. The objective of this study was to determine which maternal and infant factors to include in the mixture models to obtain the best fitting models for New Jersey state birth records. Methods: We included covariates in the models as linear predictors of the means of the component distributions and the proportion of births in each component. This allowed both the means and the proportions to vary across levels of the covariates. Results: The final model included maternal age and timing of entry into prenatal care. The proportion of births in the right-side distribution was lowest for older mothers who entered prenatal care early, higher for teen mothers who entered prenatal care early, higher still for older mothers who entered prenatal care late, and highest for teens who entered prenatal care late. Over 44% of births were classified as incorrect reported gestational age. Conclusion: These results suggest that (1) including these two covariates as linear predictors of the means and mixing proportions gives the best model for identifying births with incorrect reported gestational age, (2) late entry into prenatal care is a mechanism by which erroneously short last-menstrual-period-based gestational ages are generated, and (3) including linear predictors of the mixing proportions in the model increases the validity of the classification of incorrect reported gestational age.     

Psychosocial factors and the timing of prenatal care among women in New Jersey's HealthStart program

CONTEXT: Helping high-risk pregnant women obtain prenatal care early is the main policy goal of most U.S. publicly funded programs aimed at reducing the incidence of low birth weight and infant mortality It is therefore crucial to understand the factors that influence when women initiate prenatal care. METHODS: The effects of psychosocial and demographic risk factors on the timing of entry into prenatal care were estimated using data on roughly 90,000 Medicaid recipients who participated in New Jersey's HealthStart prenatal care program. RESULTS: Overall, 37% of women began prenatal care in the first trimester. Multivariate logistic regression indicated that women who lived in poor housing conditions and those who smoked, drank or used hard drugs had a reduced likelihood of entering care early (odds ratios, 0.8-0.9), while those who had clinical depression or who experienced domestic violence or abuse had elevated odds of early entry (1.1-1.2). The risk factor with the greatest impact on the timing of prenatal care was the wantedness of the pregnancy; women whose pregnancy was unwanted had dramatically reduced odds of entering care early (0.4). Separate analyses of women of varying racial and ethnic backgrounds demonstrated the differential effects of risk factors, the importance of including ethnicity with race and the universal impact of wantedness across racial and ethnic groups. CONCLUSIONS: Entry into prenatal care for at-risk women is affected by factors from multiple domains. It is important for prenatal programs to recognize the complexity of the issue as well as the barriers that different subgroups of women face.     

晚期早产儿中小于胎龄儿的临床回顾分析

目的 比较晚期早产儿中发生小于胎龄儿(small for gestational age, SGA)的围生期因素及新生儿的患病特点, 为能有效预防和进行早期干预提供参考依据。方法 对2010年1月-2011年12月在大连市妇产医院新生儿监护病房住院、胎龄为34~36⁺⁶周的早产儿临床资料进行回顾性分析, 比较晚期早产儿中SGA和适于胎龄儿(appropriate for gestational age, AGA)的围生期因素及新生儿期的患病情况。结果 SGA(121例)组母亲妊高症(44.6% vs 19.6%)、脐带异常(26.4% vs 5.7%)、羊水过少(24.8% vs 11.5%)、多胎妊娠(14.9% vs 6.1%)宫内窘迫(18.9% vs 8.4%)的发生比例高于AGA组(754例)(P<0.05);SGA组患儿喂养不耐受(14.9 % vs 7.6%)、低血糖(13.2% vs 7.6%)、红细胞增多症(5.8% vs 1.2%)、败血症(4.1% vs 1.5%)的发生率明显高于AGA组(P<0.05)。住院天数SGA组明显长于AGA组(10.6±4.2) d vs (6.5±5.1) d, (P<0.05)。结论 母亲妊高症、脐带异常、多胎妊娠是造成晚期早产儿SGA的主要原因, SGA患儿相对于AGA患儿具有更高的患病风险, 应针对造成SGA的围生期因素及新生儿期疾病特点进行相应的预防和干预。     

Utilisation of prenatal services and birth outcomes: a community-based study in Israel

Summary
The purpose of this paper was to assess several measures of utilisation of prenatal care as predictors of birth outcome in a community where the availability and quality of services were equal for all pregnant women. A case-control study was conducted in a small community in Israel, comparing 189 women whose pregnancy resulted in an unfavourable outcome (perinatal mortality, preterm birth and low birthweight at term) with 384 women, matched by birth order, who had a live, full-term infant weighing 2500 g or more. In a multivariable analysis, adjusting for pregnancy complications, maternal age, parity and socio-economic disadvantage, gestational age at initiation of prenatal care was not an independent predictor of unfavourable outcome; neither was lower than the recommended number of visits for the period under care. However, a higher than expected number of visits was associated with unfavourable outcome [odds ratio (OR)=6.10, 95% CI 2.09–17.78], as was non-compliance with medical recommendations [OR=2.02, 95% CI 1.24–3.29. The context of prenatal care delivery, as well as the process of care and compliance with recommendations, should be assessed in order to determine the impact of prenatal care on birth outcomes.     

Disparities in Unmet Dental Need and Dental Care Received by Pregnant Women in Maryland

To examine prenatal dental care needs, utilization and oral health counseling among Maryland women who delivered a live infant during 2001–2003 and identify the factors associated with having a dental visit and having an unmet dental need during pregnancy. Pregnancy Risk Assessment Monitoring System is an ongoing population based surveillance system that collects information of women’s attitudes and experiences before, during, and shortly after pregnancy. Logistic regression was used to model dental visits and unmet dental need using predictor variables for Maryland 2001–2003 births. Less than half of all women reported having a dental visit and receiving oral health advice during pregnancy. Twenty-five percent of women reported a need for dental care, of which 33 % did not receive dental care despite their perceived need. Multivariate modeling revealed that racial minorities, women who were not married and those with annual income <$40,000 were least likely to have a dental visit. Women who were not married, had low annual income, were older than 40 years of age, had an unintended pregnancy and received prenatal care later than desired were most likely to have an unmet dental need during pregnancy. Despite reported needs and existing recommendations to include oral health as a component of prenatal care, less than half of pregnant women have a dental visit during their pregnancy. One-third of women with a dental problem did not have a dental visit highlighting the unmet need for dental care during pregnancy.     

Prenatal care and pregnancy outcome in an HMO and general population: a multivariate cohort analysis.

We studied the use of prenatal care and pregnancy outcome in 4,148 deliveries among members of a well-established health maintenance organization (HMO) and 19,116 births among the 1973-1974 White birth cohort in the Portland, Oregon area. Mothers in the HMO were almost one year older on the average, slightly better educated, and less frequently unmarried, but had virtually identical past pregnancy histories when compared with the general population cohort. HMO members began prenatal care one month later and had three fewer visits than the general population (p less than .01); 78 per cent of the general population and only 64 per cent of HMO members began prenatal care in the first trimester (p less than .01). With maternal risk held constant, low birthweight, neonatal mortality, and infant mortality were 1.5 to 5 times greater with late, less frequent prenatal care than with early, frequent care. Multivariate analysis demonstrated a positive relationship between prenatal care and birthweight. Although this relationship was independent of risk factors recorded on birth certificates, it is not necessarily a causal relationship. Unadjusted prematurity, neonatal and infant mortality rates did not differ between the HMO and general populations. Multivariate analyses indicated that, independent of all maternal risk factors, HMO membership was associated with an increase of 30 grams in the predicted birthweight (P less than .01), but had no effect on mortality. The data suggest that, in Portland, Oregon, pregnancy outcome for HMO members is comparable to that of the general population.     

Outdoor air pollution, low birth weight, and prematurity

This study tested the hypothesis, suggested by several recent reports, that air pollution may increase the risk of adverse birth outcomes. This study analyzed all singleton live births registered by the Czech national birth register in 1991 in 67 districts where at least one pollutant was monitored in 1990-1991 (n = 108,173). Maternal exposures to sulfur dioxide (SO(2)), total suspended particles (TSP), and nitrous oxides (NO(x)) in each trimester of pregnancy were estimated as the arithmetic means of all daily measurements taken by all monitors in the district of birth of each infant. Odds ratios of low birth weight (< 2,500 g), prematurity (< 37 weeks of gestation), and intrauterine growth retardation (IUGR; < 10th percentile of birth weight for gestational age and sex) were estimated by robust logistic regression. The median (and 25th and 75th percentile) trimester exposures were 32 (18, 56) microg/m(3) for SO(2); 72 (55, 87) microg/m(3) for TSP; and 38 (23, 59) microg/m(3) for NO(x). Low birth weight (prevalence 5.2%) and prematurity (prevalence 4.8%) were associated with SO(2) and somewhat less strongly with TSP. IUGR was not associated with any pollutant. The effects on low birth weight and prematurity were marginally stronger for exposures in the first trimester, and were not attenuated at all by adjustment for socioeconomic factors or the month of birth. Adjusted odds ratios of low birth weight were 1.20 [95% confidence interval (CI), 1.11-1.30] and 1.15 (CI, 1.07-1.24) for a 50 microg/m(3) increase in SO(2) and TSP, respectively, in the first trimester; adjusted odds ratios of prematurity were 1.27 (CI, 1.16-1.39) and 1.18 (CI, 1.05-1.31) for a 50 microg/m(3) increase in SO(2) and TSP, respectively, in the first trimester. Low gestational age accounted for the association between SO(2) and low birth weight. These findings provide further support for the hypothesis that air pollution can affect the outcome of pregnancy.