Seasonal variation in the hypertensive disorders of pregnancy in Denmark

Thomsen, Christine Rohr; Henriksen, Tine Brink; Uldbjerg, Niels; Milidou, Ioanna

doi:10.1111/aogs.13786

Cited by 16 publications

(14 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Given that an individual will benefit most from supplementation when they are deficient, any potential usefulness of vitamin D in prevention will also be affected by this seasonality: while supplementation may contribute the majority of vitamin D in winter, the same treatment may be dwarfed by the abundance of skin-synthesised vitamin D in the summer, as it has been reported that 30 min of whole skin surface exposure to summer sunshine is equivalent to 10,000–20,000 IU, even in Norway 13 . The impact of season on vitamin D status 14 , 15 and association with disease traits 16 – 18 is well established and lifestyle factors may strongly affect this 19 or even reverse it 20 . Thus, the supplementation dose, duration and time of year in which a trial is carried out, as well as individual baseline status and other factors, may impact the comparisons of supplemented and placebo arms in trials 21 .…”

Section: Introductionmentioning

confidence: 99%

Power determination in vitamin D randomised control trials and characterising factors affecting it through a novel simulation-based tool

Wyse

Mangan

Zgaga

2021

Sci Rep

View full text Add to dashboard Cite

Thousands of observational studies have linked vitamin D deficiency with numerous diseases, but randomised controlled trials (RCTs) often fail to show benefit of supplementation. Population characteristics and trial design have long been suspected to undermine power but were not systematically investigated. We propose a flexible generative model to characterise benefit of vitamin D supplementation at the individual level, and use this to quantify power in RCTs. The model can account for seasonality and population heterogeneity. In a simulated 1-year trial with 1000 participants per arm and assuming a 25-hydroxyvitamin D (25OHD) increase of 20 nmol/L due to the intervention, with baseline 25OHD in the population of 15, 35, 50, 60 and 75 nmol/L, the power to detect intervention effect was 77%, 99%, 95%, 68% and 19%, respectively. The number of participants required per arm to achieve 80% power according to baseline 25OHD of 15–60 nmol/L was 1200, 400, 600 and 1400, respectively. As expected, larger increases in 25OHD due to supplementation improved power in certain scenarios. For a population baseline of 50 nmol/L, with 1500 participants in each arm, there was 100% power to detect a 20 nmol/L 25OHD increase while it was 76% for a 10 nmol/L increase. Population characteristics and trial design, including temporal considerations, have a dramatic impact on power and required sample size in vitamin D RCTs.

show abstract

Section: Introductionmentioning

confidence: 99%

Power determination in vitamin D randomised control trials and characterising factors affecting it through a novel simulation-based tool

Wyse

Mangan

Zgaga

2021

Sci Rep

View full text Add to dashboard Cite

show abstract

“…In studying the relationship between season of delivery and preeclampsia, summer was chosen as the reference month because most previous studies suggested that the prevalence associated with summer delivery was low (7,(18)(19)(20)(21). Similarly, winter was chosen as the reference season in the analysis of conception season (22)(23)(24)(25)(26).…”

Section: Discussionmentioning

confidence: 99%

“…Seven studies assessed the relationship between conception season or month and HDP. Four studies supported that conception in summer increased the risk of developing HDP (22,(24)(25)(26).…”

Section: Season Of Conception and Hdpmentioning

confidence: 98%

“…All disease-related data was extracted from medical records. Fourteen studies reported the relationship between delivery season or month and HDP (6, 7, 11, 18-21, 26-32), while seven studies reported the relationship between conception season or month and HDP (12,(22)(23)(24)(25)(26)33). The outcome de nition was not completely uniform.…”

Section: Study Characteristics and Quality Assessmentmentioning

confidence: 99%

“…Rohr Thomsen showed that women who conceived in August (OR = 1.35, 95% CI 1.11-1.64) had the highest risk of gestational hypertension, and those who conceived in June (OR = 1.17, 95% CI 0.94-1.45) had the highest risk of preeclampsia, which occurred in both the summer months (22).…”

Section: Season Of Conception and Hdpmentioning

confidence: 99%

See 2 more Smart Citations

The Association Between Season and Hypertensive Disorders in Pregnancy: a Systematic Review and Meta-analysis

et al. 2022

View full text Add to dashboard Cite

Background: There is increasing and inconsistent evidence of a relationship between hypertensive disorders of pregnancy (HDP) and season of delivery or conception.Methods: Four databases, the Cochrane Library, PubMed, EMBASE and Web of Science, were searched until September 29th, 2021. Two authors extracted data independently. A random effects model and the Mantel-Haenszel method were used to calculate pooled ORs and 95% CIs.Results: Twenty articles were included in the systematic review, and 11 articles were included in the meta-analysis. The quantitative analysis of the association between delivery season and HDP showed that the odds of HDP was higher in women who deliver in winter than in those who delivered in summer (OR=1.18, 95% CI 1.02-1.38, p < 0.001) and all other seasons (OR = 1.17, 95% CI 1.03-1.34, p <0.001). In the qualitative analysis of the association between conception season and HDP, 4 of 7 studies suggested that women who conceived in summer had a higher risk of HDP than those who conceived in other seasons.Conclusions: Based on the evidence to date, we found weakly positive relationships between HDP and summer conception and winter delivery. BackgroundHypertensive disorders of pregnancy (HDP) is a common obstetric disease, occurring in 5%-10% of all pregnancies and accounting for 10%-16% of total pregnancy-related deaths; it is the leading cause of maternal death (1, 2). HDP not only has short-term impacts during pregnancy but also longterm impacts on the health of mothers and their offspring, potentially causing maternal coronary heart disease, stroke and hypertension in offspring (3-5). At present, the precise etiology of HDP is unclear and is considered to be the result of the interaction between genes and the environment.However, a number of risk factors have been demonstrated, such as older age, low maternal educational status and multiple pregnancies (6, 7).Seasonal changes affect the occurrence and development of many diseases, such as cardiovascular diseases and autoimmune diseases (8, 9).Similarly, seasonal changes also increased the risk of maternal and neonatal mortality and the incidence of delivery complications (10). HDP deserves our attention because some studies have reported that HDP is associated with season, but the ndings have been inconsistent. Some researchers reported that the prevalence rates of gestational hypertension and preeclampsia were higher in women who delivered in winter and conceived in summer (7,11). However, some studies found no association with season (6) or found an opposite result (12).It is important to synthesize such ndings to determine which season or month of delivery or conception is related to HDP to facilitate HDP management and interventions targeting high-risk groups. MethodsThe Meta-Analysis of Observational Studies in Epidemiology (MOOSE) (13) and Preferred Reporting Items for Systematic review and Meta-Analyses (PRISMA) (14) guidelines were followed for this systematic review and meta-analysis. This study did not require ethical approval or...

show abstract

Winter, spring, summer or fall: temporal patterns in placenta-mediated pregnancy complications—an exploratory analysis

Jeppegaard

Rasmussen

Anhøj

et al. 2023

Arch Gynecol Obstet

View full text Add to dashboard Cite

Purpose Placenta-mediated pregnancy complications, like growth restriction and hypertensive disorders, are leading causes of maternal, fetal and neonatal morbidity and mortality in high-income countries. The purpose was to investigate if there is a seasonal variation in placenta-mediated pregnancy complications (small for gestational age, intrauterine growth restriction, preeclampsia, preterm birth and intrauterine fetal death). Methods This is a Danish cohort study including all singleton deliveries at gestational week 22 up to and including week 41 conceived from December 2006 to November 2016 (N = 555,459). We used statistical process control charts to visualize data and to test for patterns of non-random variation in data over time for pregnancies with risk factors (BMI, diabetes, in vitro fertilization, maternal age > 40 years, primipara, previous caesarean and smoking) and each of the following outcome: fetal growth restriction, hypertensive disorders, preterm birth and intrauterine fetal death. The study was approved by the Danish Data Protection agency; REG-039-2019. Results We found a seasonal pattern in hypertensive disorders during pregnancy with dips in pregnancies conceived in the fall season and highest risk by conception in the spring and summer season. We found no apparent seasonality in cases of preterm delivery, small for gestational age and intrauterine mortality. Individual risk factors (e.g. smoking and obesity) for placenta-mediated complicated over time were in consistency with the general trends. Conclusions We found a significant seasonal variation in the risk of hypertensive disorders of pregnancy with highest risk by conception in the spring and summer season. This study found no seasonal variation in other placenta-mediated complications.

show abstract

Seasonal variation in the hypertensive disorders of pregnancy in Denmark

Cited by 16 publications

References 30 publications

Power determination in vitamin D randomised control trials and characterising factors affecting it through a novel simulation-based tool

Power determination in vitamin D randomised control trials and characterising factors affecting it through a novel simulation-based tool

The Association Between Season and Hypertensive Disorders in Pregnancy: a Systematic Review and Meta-analysis

Winter, spring, summer or fall: temporal patterns in placenta-mediated pregnancy complications—an exploratory analysis

Contact Info

Product

Resources

About