The birth weight "paradox" uncovered?

Low birth weight (LBW) infants have lower infant mortality in groups in which LBW is most frequent. For example, in 1991, US infants born to smokers had higher risks of both LBW and infant mortality than infants born to nonsmokers. However, among LBW infants, infant mortality was lower for infants born to smokers (relative rate = 0.79). There are competing theories regarding this so-called "paradox." One is that maternal smoking is beneficial for LBW infants. The authors use causal diagrams to show that, even in the absence of any beneficial effect of smoking, an inverse association due to stratification on birth weight can be found. This variable is affected by the exposure of interest and shares common causes with the outcome. That is, LBW infants born to smokers may have a lower risk of mortality than other LBW infants whose LBW is due to causes associated with high mortality (e.g., birth defects). Under realistic causal diagrams, adjustment for birth weight is unwarranted when the analytical goal is to estimate overall effects of prenatal variables on infant mortality. Even for estimating direct effects of prenatal variables, adjustment for birth weight may be invalid when there is an unmeasured common cause of LBW and mortality. An appropriate justification for conditioning on birth weight requires specifying 1) the causal question motivating this analytical approach and 2) the assumptions regarding the proposed underlying biologic mechanisms.     

Why carry out a longitudinal birth survey?

In spite of technological progress throughout the world, ill health, both physical and mental, is widespread – but much of this is preventable. With rapid globalisation, populations in both industrialised and developing countries are being exposed to various stresses and to new environmental factors, such as those related to climate change and to an increasing range of chemicals of unknown effect. There is substantial evidence that exposures to environmental risk factors in pregnancy and childhood have a major influence on health and development even into adulthood and future generations. In this paper we discuss the importance of longitudinal studies in identifying the processes underlying health and developmental problems and thus, by using the strengths of birth cohort studies, identifying preventative and other strategies which will protect public health from adverse environmental influences.     

Cost effects of preterm birth: a comparison of health care costs associated with early preterm,late preterm,and full-term birth in the first 3 years after birth

Preterm birth is one of the main causes for infant morbidity and mortality. Apart from negative health outcomes, preterm birth also produces significant health care expenditures. This study evaluates the costs associated with preterm birth in different health sectors during the first 3 years of infants’ lives. In a retrospective observational study based on claims data from a German statutory health insurance company, average costs for medication, hospital treatment, ambulatory treatment, and non-medical remedies during the first 3 years after birth were analyzed for early preterm, late preterm, and full-term births. Costs associated with preterm births were generally higher than for full-term births, with the highest costs for the hospital treatment of early preterm births. Cost differences tended to decrease in the second and third year after birth except for ambulatory treatment costs, which decreased for late preterm and full-term births but not for early preterm births. The study shows that preterm birth is associated with increased health care costs, particularly during the first year after birth, indicating that the implementation of adequate programs and policies for preventing preterm birth is not only desirable from a medical but also from a health economic perspective.     

Which factors could explain the low birth weight paradox?

OBJECTIVE: Low birth weight children are unusual among well-off families. However, in Brazil, low birth weight rate was higher in a more developed city than in a less developed one. The study objective was to find out the reasons to explain this paradox. METHODS: A study was carried out in two municipalities, Ribeir?o Preto (Southeastern Brazil) and S?o Luís (Northeastern Brazil), which low birth weight rates were 10.7% and 7.6% respectively. Data from two birth cohorts were analyzed: 2,839 newborns in Ribeir?o Preto in 1994 and 2,439 births in S?o Luís in 1997-1998. Multiple logistic regression analysis was performed, adjusted for confounders. RESULTS: Low birth weight risk factors in S?o Luís were primiparity, maternal smoking and maternal age less than 18 years. In Ribeir?o Preto, the associated variables were family income between one and three minimum wages, maternal age less than 18 and equal to or more than 35 years, maternal smoking and cesarean section. In a combined model including both cohorts, Ribeir?o Preto presented a 45% higher risk of low birth weight than S?o Luís. When adjusted for maternal smoking habit, the excess risk for low birth weight in Ribeir?o Preto compared to S?o Luís was reduced by 49%, but the confidence interval was marginally significant. Differences in cesarean section rates between both cities contributed to partially explain the paradox. CONCLUSIONS: Maternal smoking was the most important risk factor for explaining the difference in low birth weight between both cities. The other factors contributed little to explain the difference in low birth weight rates.     

Are gestational age,birth weight,and birth length indicators of favorable fetal growth conditions? A structural equation analysis of Filipino infants

The fetal origins hypothesis emphasizes the life‐long health impacts of prenatal conditions. Birth weight, birth length, and gestational age are indicators of the fetal environment. However, these variables often have missing data and are subject to random and systematic errors caused by delays in measurement, differences in measurement instruments, and human error. With data from the Cebu (Philippines) Longitudinal Health and Nutrition Survey, we use structural equation models, to explore random and systematic errors in these birth outcome measures, to analyze how maternal characteristics relate to birth outcomes, and to take account of missing data. We assess whether birth weight, birth length, and gestational age are influenced by a single latent variable that we call favorable fetal growth conditions (FFGC) and if so, which variable is most closely related to FFGC. We find that a model with FFGC as a latent variable fits as well as a less parsimonious model that has birth weight, birth length, and gestational age as distinct individual variables. We also demonstrate that birth weight is more reliably measured than is gestational age. FFGCs were significantly influenced by taller maternal stature, better nutritional stores indexed by maternal arm fat and muscle area during pregnancy, higher birth order, avoidance of smoking, and maternal age 20–35 years. Effects of maternal characteristics on newborn weight, length, and gestational age were largely indirect, operating through FFGC. Copyright © 2013 John Wiley & Sons, Ltd.     

How useful are registered birth statistics for health and social policy? A global systematic assessment of the availability and quality of birth registration data

Background

The registration and certification of births has a wide array of individual and societal benefits. While near-universal in some parts of the world, birth registration is less common in many low- and middle-income countries, and the quality of vital statistics vary. We assembled publicly available birth registration records for as many countries as possible into a novel global birth registration database, and we present a systematic assessment of available data.

Methods

We obtained 4918 country-years of data from 145 countries covering the period 1948–2015. We compared these to existing estimates of total births to assess completeness of public data and adapted existing methods to evaluate the quality and timeliness of the data.

Results

Since 1980, approximately one billion births were registered and shared in public databases. Compared to estimates of fertility, this represents only 40.0% of total births in the peak year, 2011. Approximately 74 million births (53.1%) per year occur in countries whose systems do not systematically register them and release the aggregate records. Considering data quality, timeliness, and completeness in country-years where data are available, only about 12 million births per year (8.6%) occur in countries with high-performing registration systems.

Conclusions

This analysis highlights the gaps in available data. Our objective and low-cost approach to assessing the performance of birth registration systems can be helpful to monitor country progress, and to help national and international policymakers set targets for strengthening birth registration systems.

     

Why do Mexican Americans give birth to few low-birth-weight infants?

There are relatively few low-weight births among Mexican Americans, despite their socioeconomic disadvantages. Fewer low-birth-weight (LBW) births result when babies are heavier at term or when there are fewer preterm deliveries. The authors used 1994 US singleton livebirth birth certificates to compare Mexican Americans with non-Hispanic Whites. They found that the lower LBW rate among Mexican Americans (5.8%) compared with non-Hispanic Whites (6.1%) occurred because fewer small, preterm babies were born to Mexican Americans (3.4% vs. 3.9%). This result was obscured by two findings. First, the mean birth weight of Mexican American babies (3,343 g) was lower than that of non-Hispanic White babies (3,393 g). This finding again showed the independence of mean birth weight and LBW. Second, the overall preterm birth rate was higher among Mexican Americans (10.6%) than non-Hispanic Whites (9.3%). Our hypothesis is that this finding reflects errors in recorded gestational age, as illustrated by a strongly bimodal birth-weight distribution at young gestational ages for Mexican Americans. Further studies on the LBW paradox among Mexican Americans should thus focus on gestational age more than on birth weight.     

Perceptions of the birth experience: A cross‐cultural comparison

A comparison of 66 Calgary, Alberta and 294 San Francisco, California first‐time mothers’ perceptions of their birth experiences following vaginal and cesarean births found that both populations perceived the surgical birth less positively. The Calgary group of women as a whole tended to be more traditional in their plans and attitudes toward motherhood; they attended prenatal classes more often, and fewer planned to return to work after the birth of the baby. There were no significant differences in the two populations for those choosing to breastfeed; however, within the combined populations, breastfeeders perceived their birth experience more positively.     

Are racial disparities in preterm birth larger in hypersegregated areas?

The causes of the racial/ethnic disparity in preterm birth (PTB) remain largely unknown; traditional risk factors such as smoking and prenatal care fail to account for it. The authors examined whether living in metropolitan areas (MAs) with high levels of residential racial segregation along multiple dimensions (hypersegregation) was associated with higher rates of PTB or larger racial disparities in PTB and whether segregation modified the established race-age association in PTB. The authors merged 2000 natality data (n = 1,944,703) with US Census measures of Black-White hypersegregation. They executed two-level hierarchical logistic regression analyses among White and Black mothers in 237 MAs to estimate the odds of PTB by hypersegregation, race, and age, after controlling for covariates. In unadjusted and adjusted models, Black infants in hypersegregated MAs were more likely to be preterm than Black infants in nonhypersegregated MAs (p < 0.001). Black-White PTB disparities were larger in hypersegregated areas than in nonhypersegregated areas (p < 0.001), and the age-race association with PTB was modified by hypersegregation (p < 0.001). Living in a hypersegregated MA had a more pronounced association with PTB among older Black women, and racial disparities in PTB were larger in hypersegregated areas among older mothers (p < 0.001). Since over 40% of Black childbearing women live in hypersegregated areas, residential segregation may be an important social determinant of racial birth disparities.     

To what extent are women free to choose where to give birth? How discourses of risk,blame and responsibility influence birth place decisions

Over the past 50 years, two things have changed for women giving birth in high-income nations; birth has become much safer, and now takes place in hospital rather than at home. The extent to which these phenomena are related is a source of ongoing debate, but concern about high intervention rates in hospitals, and financial pressures on health care systems, have led governments, clinicians and groups representing women to support a return to birth in ‘alternative’ settings such as midwife-led birth centres or at home, particularly for well women with healthy pregnancies. Despite this, most women still plan to give birth in high-technology hospital labour wards. In this article, we draw on a longitudinal narrative study of pregnant women at three maternity services in England between October 2009 and November 2010. Our findings indicate that for many women, hospital birth with access to medical care remained the default option. When women planned hospital birth, they often conceptualised birth as medically risky, and did not raise concerns about overuse of birth interventions; instead, these were considered an essential form of rescue from the uncertainties of birth. Those who planned birth in alternative settings also emphasised their intention, and obligation, to seek medical care if necessary. Using sociocultural theories of risk to focus our analysis, we argue that planning place of birth is mediated by cultural and historical associations between birth and safety, and further influenced by prominent contemporary narratives of risk, blame and the responsibility. We conclude that even with high-level support for ‘alternative’ settings for birth, these discourses constrain women’s decisions, and effectively limit opportunities for planning birth in settings other than hospital labour wards. Our contention is that a combination of cultural and social factors helps explain the continued high uptake of hospital obstetric unit birth, and that for this to change, birth in alternative settings would need to be positioned as a culturally normative and acceptable practice.     

Planned home birth in Slovenia—Are we ready?

Nowadays, women want a more intimate and familiar atmosphere during labour, which results in increased planned home birth rates. Every woman has the autonomy to decide where she will give birth; however, it is important that she is informed of risks and advantages beforehand. Home births can be distinguished between planned and unplanned home births. Planned home births can be conducted by professional birth attendants (licensed midwives) or birth assistants (doulas, etc). The rates of Slovenian women who decided to deliver at home are increasing year by year. Researches on home births still present discordant data about home birth safety. Their findings have shown that the main advantage of home birth is a spontaneous birth without medical interventions, especially in multiparous low‐risk women. The main disadvantage, however, is a higher risk for neonatal death, in particular on occurrence of complications requiring a transfer to hospital and surgical intervention. Global guidelines emphasize careful selection of candidates suitable for home birth, well‐informed pregnant women, education of birth attendants, and strict formation of transfer indications.