Trends of abnormal birthweight among full-term infants in Newfoundland and Labrador

Birthweights at term have increased globally: insights from a systematic review of 183 million births

OBJECTIVE

This study aimed to assess global trends in mean birthweights at term, as reported in peer-reviewed literature.

DATA SOURCES

We electronically searched PubMed, Embase, and Web of Science up to September 2023, using combinations of the search terms: "birth weight"; "birth-weight"; "birthweight"; "trend". There were no restrictions based on language or geographic area.

STUDY ELIGIBILITY CRITERIA

We included all ecological and observational studies reporting mean birthweight at term as a continuous numerical variable over time.

METHODS

We assessed the quality of included studies using the Dufault and Klar checklist modified by Betran et al. Univariate and multivariate linear models were used to examine the effects of time (years) and geographical origins. Subgroup analyses focused on national data sources and on data collected from 1950 onward.

RESULTS

Among 6447 reviewed articles, 29 met our criteria, reporting mean birthweight data from over 183 million infants worldwide. Most studies were hospital-based (48.3%), 44.8% used national data, and a minority used municipality, community, or regional data (6.9%). Geographically, North America (31.0%) had the highest representation, followed by Asia and Europe (27.6% each), and South America and Oceania (6.9% each). Our univariate linear regression model (Model 1) revealed a significant increase in mean birthweight at term over time (4.74 g/y; 95% confidence interval, 3.95-5.53; P<.001). Model 2, incorporating continental dummy variables into the first model, confirmed this trend (3.85 g/y; 95% confidence interval, 2.96-4.74; P<.001). Model 3, focusing on available national data, did not find a significant relationship. Model 4 narrowed its focus on records from 1950 onward, reporting a robust annual increase of 7.26 g/y (95% confidence interval, 6.19-8.33; P<.001). Model 5, adjusting for the number of participants included in each study, reported a conclusive mean term birthweight increase of 1.46 g/y (95% confidence interval, 0.74-2.18; P<.001).

CONCLUSION

This systematic review of 29 studies shows an increase in term birthweights over time, particularly when considering data since 1950. Limitations include study quality variations, data source diversity, and data sparsity, underscoring the need for future research to use precise gestational age distinctions and predetermined time frames to gain a deeper understanding of this trend and its implications for maternal and child health.

Secular trends of socio-demographic and lifestyle characteristics among delivering women in Arctic Russia, 1973-2017

The aim of this study was to describe temporal trends in socio-demographic and lifestyle characteristics among delivering women in two Northern provinces of Russia from 1973 to 2017. Totally 161,730 births were registered in three birth registries. Changes in the distribution of maternal age, education, marital status, smoking during pregnancy were studied using Pearson's chi-squared tests and one-way ANOVA. The logistic regression models were used to assess factors, contributing to the variations in the prevalence of maternal smoking. The mean age of primiparous mothers increased from 22.1 years in 1973-1980 to 25.4 years in 2012-2017 (p < 0.001). The proportion of primiparous mothers with higher education increased from 26.2% in 2006 to 38.3% in 2017 (p < 0.001). The proportion of cohabiting primiparous women increased from 5.0% to 15.2% over the study period (p < 0.001). The proportion of mothers smoking during pregnancy decreased from 18.9% in 2006-2011 to 14.8% in 2012-2017 (p < 0.001). Downward in the prevalence of smoking was revealed in 2012-2017 compared to 2006-2011 (OR = 137.76; 95%CI:71.62-264.96, OR = 183.74; 95%CI:95.52-353.41, respectively). Over the past decades, women postpone childbearing until receiving higher education, continue living in cohabitation during pregnancy and smoke less.

Longitudinal Rates and Risk Factors for Adverse Birth Weight Among First Nations Pregnancies in Alberta

OBJECTIVE

We wished to identify the prevalence, longitudinal trends, and associated risk factors for various birth weight categories by First Nations ethnicity in the province of Alberta.

METHODS

We performed a retrospective analysis of administrative data for the years 2000 to 2009 inclusive. Age-adjusted prevalence trends for high birth weight (HBW; > 4000g), very HBW (> 4500g), low birth weight (LBW; < 2500g), and very LBW (< 1500g) were compared via average annual percent change analyses. Logistic regression analysis was used to determine risk factors.

RESULTS

First Nations ethnicity was a significant independent predictor of HBW (OR 1.82 [95% CI 1.75, 1.89]), very HBW (OR 2.35 [95% CI 2.18, 2.52]), and very LBW (OR 1.35 [95% CI 1.23, 1.48]), but not of LBW (OR 0.98 [95% CI 0.93, 1.03]). However, HBW prevalence decreased and other birth weight categories remained stable over time in First Nations populations. Gestational diabetes and maternal weight ≥ 91 kg were potentially manageable risk factors for HBW. Potentially manageable risk factors for LBW included pre-gestational renal disease, hypertension, and maternal weight ≤ 45 kg, as well as smoking, illicit drug dependence, and alcohol consumption.

CONCLUSION

Although HBW, very HBW, and very LBW remain more common in Alberta First Nations populations than in the general population, their prevalence is not increasing.

Changes in perinatal health in two birth cohorts (1997/1998 and 2010) in São Luís, Maranhão State, Brazil

The objective of this study was to analyze changes in perinatal health in two birth cohorts started in 1997/1998 and 2010, respectively, in São Luís, Maranhão State, Brazil. A total of 2,493 live born infants were included in 1997/1998 and 5,166 in 2010. Low birth weight (LBW) rate did not change (8.5% in 1997/1998 and 8.6% in 2010). Preterm birth (PTB) rate also remained stable (13.2% in 1997/1998 and 13% in 2010). Teenage deliveries and births to single mothers decreased. Maternal schooling and prenatal care coverage increased. Intrauterine growth restriction (IUGR) decreased from 13.3% to 10.6% (p < 0.001). The perinatal mortality rate decreased from 36.6 to 20.7 per 1,000 (p < 0.001) and the infant mortality rate (IMR) dropped from 28.5 to 12.8 per 1,000 (p < 0.001). The cesarean rate increased from 34.1% to 47.5% (p < 0.001). In conclusion, despite favorable changes in socio-demographic, behavioral, and health service factors and decreasing rates of IUGR and perinatal and infant mortality, LBW and PTB remained stable, while the cesarean rate increased.

Changes in birth weight between 2002 and 2012 in Guangzhou, China

Background

Recent surveillance data suggest that mean birth weight has begun to decline in several developed countries. The aim of this study is to examine the changes in birth weight among singleton live births from 2002 to 2012 in Guangzhou, one of the most rapidly developed cities in China.

Methods

We used data from the Guangzhou Perinatal Health Care and Delivery Surveillance System for 34108 and 54575 singleton live births with 28–41 weeks of gestation, who were born to local mothers, in 2002 and 2012, respectively. The trends in birth weight, small (SGA) and large (LGA) for gestational age and gestational length were explored in the overall population and gestational age subgroups.

Results

The mean birth weight decreased from 3162 g in 2002 to 3137 g in 2012 (crude mean difference, −25 g; 95% CI, −30 to −19). The adjusted change in mean birth weight appeared to be slight (−6 g from 2002 to 2012) after controlling for maternal age, gestational age, educational level, parity, newborn's gender and delivery mode. The percentages of SGA and LGA in 2012 were 0.6% and 1.5% lower than those in 2002, respectively. The mean gestational age dropped from 39.2 weeks in 2002 to 38.9 weeks in 2012. In the stratified analysis, we observed the changes in birth weight differed among gestational age groups. The mean birth weight decreased among very preterm births (28–31 weeks), while remained relatively stable among other gestational age subcategories.

Conclusions

Among local population in Guangzhou from 2002 to 2012, birth weight appeared to slightly decrease. The percentage of SGA and LGA also simultaneously dropped, indicating that newborns might gain a healthier weight for gestational age.

Declines in birth weight and fetal growth independent of gestational length

OBJECTIVE

To estimate whether the decrease in birth weight of term singletons in the United States and elsewhere over the past decade, despite trends in common maternal characteristics expected to contribute toward an increase, is attributable to the simultaneous decrease in gestational length.

METHODS

Using data from Intermountain Healthcare, where a successful initiative reduced the number of early-term (37-38 weeks) elective deliveries, we examined trends in birth weight, being small for gestational age (SGA), and being large for gestational age (LGA) among 219,694 singleton neonates born between July 2000 and December 2008 at 37-41 weeks of gestation.

RESULTS

Over the 8.5 years, births through scheduled deliveries at 37-38 weeks decreased (9.7-4.4%), but overall scheduled deliveries increased (29-34%) and mean gestational age at birth (39.1 weeks) did not change. Mean birth weight (3,410-3,383 g) and LGA status (9.0-7.4%) both decreased, whereas SGA increased (7.5-8.2%). In multivariable analyses adjusting for maternal and newborn characteristics, birth weight decreased (-36 g; 95% confidence interval [CI] -31 to -42), especially among neonates born at 37-38 weeks of gestation (-40 g; 95% CI -30 to -49) or among those with medical indications for urgent deliveries (-48 g; 95% CI -34 to -63). Odds of being LGA decreased (0.77; 95% CI 0.73-0.82) and odds of being SGA increased (1.12; 95% CI 1.06-1.19).

CONCLUSION

Even in a population in which gestational length did not change, birth weight and fetal growth declined. Decrease not only in gestational length but also in fetal growth is likely to be contributing to the widely observed recent decrease in birth weight.

LEVEL OF EVIDENCE

I.