ArticleAmerican journal of obstetrics and gynecology2017
Confounding, causality, and confusion: the role of intermediate variables in interpreting observational studies in obstetrics.
Article in American journal of obstetrics and gynecology, 2017. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 145 papers, 6 of them syntheses that pooled 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.
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.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
145 citing papers in PubMed, 6 syntheses or guidelines pooled it, 309 citations in OpenAlex.
- Estimating Causal Effects of Third-Stage Management on Postpartum Haemorrhage in a Midwifery Context: An Evidence Synthesis Approach for Constructing Directed Acyclic Graphs.Paediatric and perinatal epidemiology · 2026Pooled it
- Does the evidence support in utero influences on later health and disease? A systematic review of highly cited Barker studies on developmental origins.Journal of perinatology : official journal of the California Perinatal Association · 2024Pooled it
- Gestational age at birth and body size from infancy through adolescence: An individual participant data meta-analysis on 253,810 singletons in 16 birth cohort studies.PLoS medicine · 2023Pooled it
- Advanced paternal age is associated with an increased risk of spontaneous miscarriage: a systematic review and meta-analysis.Human reproduction update · 2020Pooled it
- Association of Histological and Clinical Chorioamnionitis With Neonatal Sepsis Among Preterm Infants: A Systematic Review, Meta-Analysis, and Meta-Regression.Frontiers in immunology · 2020Pooled it
- Short interpregnancy intervals and adverse perinatal outcomes in high-resource settings: An updated systematic review.Paediatric and perinatal epidemiology · 2019Pooled it
- Do smoking abstinence periods among pregnant smokers improve birth weight? A secondary analysis of a randomised, controlled trial.BMJ open · 2024Trial
- Meconium-stained amniotic fluid and neonatal morbidity in nulliparous patients with prolonged pregnancy.Acta obstetricia et gynecologica Scandinavica · 2023Trial
- Perinatal and Maternal Outcomes by Indication for Delivery in the Second Trimester.American journal of perinatology · 2026Observational
- Exploring hormonal influences on nicotine craving and use across the perinatal period: A prospective longitudinal study.Drug and alcohol dependence reports · 2026Article
- Association between annual twin delivery volume and severe postpartum hemorrhage in twin pregnancies.International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics · 2026Observational
- Contributions of preeclampsia to preterm delivery: a hypothetical interventional cohort study using incremental propensity scores.International journal of epidemiology · 2026Article
- Maternal Cardiovascular Health During Pregnancy and Offspring Developmental Delay.JAMA network open · 2026Article
- Beyond the Headlines: Examining the Evidence Around Acetaminophen and Autism Risk.The journal of pediatric pharmacology and therapeutics : JPPT : the official journal of PPAG · 2026Article
- Association between a Periconception Healthy Plant-Based Diet and Adverse Pregnancy Outcomes.The Journal of nutrition · 2026Article
- Postnatal conditional growth and size and body composition at 24 months in moderate-and-late preterm children.Pediatric research · 2026Article
- Neighborhood socioeconomic disadvantage and chorioamnionitis.Journal of perinatology : official journal of the California Perinatal Association · 2026Article
- Maternal prenatal stress and infant temperament at one year: exploring the mediating role of postpartum depression in the French EDEN cohort.Archives of women's mental health · 2026Article
- Placental Abruption, Preterm Delivery, and Cardiovascular Disease in Twin Offspring.Journal of the American Heart Association · 2026Article
- Covariate adjustment in LGBTQ+ health disparities research: aligning methods with assumptions.American journal of epidemiology · 2026Article
85 more citing papers are in PubMed but not listed here.
Corrections and comments
- Commented on by
- Commented on byReply.2018
Authors and funding
2 authors at 2 institutions in 1 country.
Funding
Abstract
Prospective and retrospective cohorts and case-control studies are some of the most important study designs in epidemiology because, under certain assumptions, they can mimic a randomized trial when done well. These assumptions include, but are not limited to, properly accounting for 2 important sources of bias: confounding and selection bias. While not adjusting the causal association for an intermediate variable will yield an unbiased estimate of the exposure-outcome's total causal effect, it is often that obstetricians will want to adjust for an intermediate variable to assess if the intermediate is the underlying driver of the association. Such a practice must be weighed in light of the underlying research question and whether such an adjustment is necessary should be carefully considered. Gestational age is, by far, the most commonly encountered variable in obstetrics that is often mislabeled as a confounder when, in fact, it may be an intermediate. If, indeed, gestational age is an intermediate but if mistakenly labeled as a confounding variable and consequently adjusted in an analysis, the conclusions can be unexpected. The implications of this overadjustment of an intermediate as though it were a confounder can render an otherwise persuasive study downright meaningless. This commentary provides an exposition of confounding bias, collider stratification, and selection biases, with applications in obstetrics and perinatal epidemiology.
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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.