Evidence map›Paper›PMID 33148618›Full record

SynthesisBMJ (Clinical research ed.)2020

Associations between high temperatures in pregnancy and risk of preterm birth, low birth weight, and stillbirths: systematic review and meta-analysis.

Matthew Francis Chersich, Minh Duc Pham, Ashtyn Areal, Marjan Mosalam Haghighi, Albert Manyuchi, Callum P Swift, Bianca Wernecke, Matthew Robinson, Robyn Hetem, Melanie Boeckmann and 2 more

Registry-linked trialOpen access · hybridAbstract readMeta-AnalysisSystematic Review
PubMed Full text at PMC Publisher
In one paragraph

Synthesis in BMJ (Clinical research ed.), 2020. The graph could read no effect estimate from its abstract, so it casts no vote on the map. It is linked to trial NCT07489664 (Indigenous Nutritional Supplements for Pregnancy to Improve Resilience in Environmental Heat), which is not on this map. Cited by 279 papers, 9 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
279citing papers in PubMed, 9 pooled it
23.1field-weighted citation impact, top 1% of its field
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

NCT07489664 nanot yet recruitingnot on this mapstarted 2026, after this paper: background citation

Indigenous Nutritional Supplements for Pregnancy to Improve Resilience in Environmental Heat

TypeinterventionalSponsorAga Khan UniversityRan2026 to 2028Enrolled292ConditionsHeat Stress, Pregnancy, Women of Reproductive Age, Nutrition StatusArmsIndigenous Balanced Diet Arm
3 · Its place in the literature

Who cites it

279 citing papers in PubMed, 9 syntheses or guidelines pooled it, 556 citations in OpenAlex.

  1. Pooled it
  2. Guideline
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  5. Evaluating the Impact of Heat Stress on Placental Function: A Systematic Review.International journal of environmental research and public health · 2024
    Pooled it
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  10. Trial
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  12. Article
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219 more citing papers are in PubMed but not listed here.

4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

12 authors at 9 institutions in 5 countries.

Matthew Francis ChersichWits Reproductive Health and HIV Institute, Faculty of Health Sciences, University of the Witwatersrand, Hillbrow, Johannesburg 2001, South Africa mchersich@wrhi.ac.za.ORCID 0000-0002-4320-9168
Minh Duc PhamBurnet Institute, Melbourne, VIC, Australia.
Ashtyn ArealLeibniz Research Institute for Environmental Medicine, Düsseldorf, Germany.
Marjan Mosalam HaghighiThe Children's Hospital at Westmead, Cardiology Centre, University of Sydney, Sydney, NSW, Australia.
Albert ManyuchiGlobal Change Institute, University of the Witwatersrand, Johannesburg, South Africa.
Callum P SwiftTallaght University Hospital, Dublin, Ireland.
Bianca WerneckeEnvironment and Health Research Unit, South African Medical Research Council, Johannesburg, South Africa.
Matthew RobinsonDepartment of Health, Dublin, Ireland.
Robyn HetemSchool of Animal, Plant and Environmental Sciences, Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa.
Melanie BoeckmannDepartment of Environment and Health, School of Public Health, Bielefeld University, Germany.
Shakoor HajatDepartment of Public Health, Environments and Society, and the Centre on Climate Change and Planetary Health, London School of Hygiene and Tropical Medicine, London, UK.
Climate Change and Heat-Health Study Group
University of the Witwatersrand · ZABielefeld University · DEBurnet Institute · AUDepartment of Health · IELeibniz Institute of Environmental Medicine · DELondon School of Hygiene & Tropical Medicine · GBSouth African Medical Research Council · ZATallaght University Hospital · IEThe University of Sydney · AU

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

objectiveTo assess whether exposure to high temperatures in pregnancy is associated with increased risk for preterm birth, low birth weight, and stillbirth.

designSystematic review and random effects meta-analysis. DATA SOURCES: Medline and Web of Science searched up to September 2018, updated in August 2019. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Clinical studies on associations between high environmental temperatures, and preterm birth, birth weight, and stillbirths.

results14 880 records and 175 full text articles were screened. 70 studies were included, set in 27 countries, seven of which were countries with low or middle income. In 40 of 47 studies, preterm births were more common at higher than lower temperatures. Exposures were classified as heatwaves, 1°C increments, and temperature threshold cutoff points. In random effects meta-analysis, odds of a preterm birth rose 1.05-fold (95% confidence interval 1.03 to 1.07) per 1°C increase in temperature and 1.16-fold (1.10 to 1.23) during heatwaves. Higher temperature was associated with reduced birth weight in 18 of 28 studies, with considerable statistical heterogeneity. Eight studies on stillbirths all showed associations between temperature and stillbirth, with stillbirths increasing 1.05-fold (1.01 to 1.08) per 1°C rise in temperature. Associations between temperature and outcomes were largest among women in lower socioeconomic groups and at age extremes. The multiple temperature metrics and lag analyses limited comparison between studies and settings.

conclusionsAlthough summary effect sizes are relatively small, heat exposures are common and the outcomes are important determinants of population health. Linkages between socioeconomic status and study outcomes suggest that risks might be largest in low and middle income countries. Temperature rises with global warming could have major implications for child health. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD 42019140136 and CRD 42018118113.

Indexed as

Infant, Low Birth WeightFemaleHot TemperatureHumansInfant, NewbornPregnancyPremature BirthRisk FactorsStillbirth

Identifiers

PMID33148618
PMCPMC7610201
OpenAlexW3095952743

What OpenQuestion holds

Textmetadata
LicenceCC BY-NC
Read underepoch 390

Registered trials

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.