Increasing birthweight over time reported

Increasing birthweight over time reported | Image Credit: © Gary - © Gary - stock.adobe.com.

An increase in term birthweights over time has been observed since 1950, according to a recent study published in the American Journal of Obstetrics & Gynecology.¹

Maternal and fetal health factors have significantly changed in the past few decades, impacting birthweight dynamics. Fetal, maternal, and placental factors have been primarily linked to birthweight, but data has also indicated potential influences from parity, age, and maternal anthropometry.

Along with affecting offspring health outcomes, there may be an association between large for gestational age (LGA) and diabetes risk in mothers.² In a recent study, the risk of diabetes or prediabetes onset within 10 to 14 years was increased 21% among women with an LGA delivery vs appropriate for gestational age.

While certain countries have identified trends of increasing birthweight, there is a need for a comprehensive synthesis of global literature.¹ However, understanding these trends is crucial for determining outcomes in public health.

To evaluate temporal trends in mean birthweights on a global scale, investigators conducted a systematic literature review. Articles from January 1950 to September 2023 were obtained from the PubMed, Embase, and Web of Science databases.

Eligibility criteria included being an ecological or observational study reporting the mean birthweight at term as a numerical continuous variable. Studies only reporting the mean birthweight as a categorial variable, disregarding gestational age, involving interventions, and being a case series with under 10 cases or a case report were excluded.

Title screening was performed by 2 reviewers who consulted to resolve disagreements. Additional screening included title and abstract, full text, and critical appraisal. The 2 reviewers independently extracted data about mean birthweight at term, as well as mean gestational age and mean annual number of cases when available.

Birthweight was rounded to the nearest whole number in grams. Additionally, data from studies evaluating more than 1 cohort was classified based on differences in gestational age, sex, or geographic origin.

There were 29 studies included in the final analysis, encompassing 63 distinct cohorts and including mean term birthweight data from over 183 million infants. Of studies, 48.3% were hospital-based, 44.8% utilized national registries, and 6.9% were from municipality, community, or regional sources.

North America was the location of 31% of studies, Asia and Europe 27.6% each, and South America and Oceania 6.9% each. Sample sizes above 20% and up to 100% were reported in 28.6% of studies.

Data indicated a significant increase in the mean term birthweight of 4.74 g per year reported from municipality, community, or regional sources. When addressing geographical variations, this annual increase was 3.85 g.

A statistically significant increase in annual mean term birthweight was not observed when only incorporating data from national sources. However, a mean increase of 7.26 g per year was reported when including records from 1950 onward. Finally, when adjusting for the number of participants in each study, the annual mean birthweight increase was 1.46 g.

These results indicated a significant increase in mean birthweight in years measured over time. Investigators recommended more robust research with larger sample sizes and more distinct gestational age groups to provide a more nuanced perspective on maternal and child health implications.

References

1. Bonanni G, Airoldi C, Berghella V. Birthweights at term have increased globally: insights from a systematic review of 183 million births. American Journal of Obstetrics & Gynecology. 2024;231(4):395-407.E4. doi:10.1016/j.ajog.2024.03.002
2. Campbell P. Large for gestational age births could increase diabetes risk in women. Contemporary OB/GYN. February 13, 2023. Accessed September 25, 2024. https://www.contemporaryobgyn.net/view/large-for-gestational-age-births-could-increase-diabetes-risk-in-women