Research
Print page Print page
Switch language
The Capital Region of Denmark - a part of Copenhagen University Hospital
Published

Incidences of obstetric outcomes and sample size calculations: A Danish national registry study based on all deliveries from 2008 to 2015

Research output: Contribution to journalJournal articleResearchpeer-review

DOI

  1. Human papilloma virus vaccination and its real-life efficacy

    Research output: Contribution to journalJournal articleResearchpeer-review

  2. Current use of noninvasive prenatal testing in Europe, Australia and the USA: A graphical presentation

    Research output: Contribution to journalJournal articleResearchpeer-review

  3. Implementation of exome sequencing in fetal diagnostics - data and experiences from a tertiary center in Denmark

    Research output: Contribution to journalJournal articleResearchpeer-review

  4. "It's probably nothing, but…" Couples' experiences of pregnancy following an uncertain prenatal genetic result

    Research output: Contribution to journalJournal articleResearchpeer-review

  5. Non-invasive prenatal testing and maternal obesity - A review

    Research output: Contribution to journalReviewResearchpeer-review

  1. Women and partners' experiences of critical perinatal events: a qualitative study

    Research output: Contribution to journalJournal articleResearchpeer-review

  2. Multivitamin use and risk of preeclampsia in a high-income population: A cohort study

    Research output: Contribution to journalJournal articleResearchpeer-review

  3. Adherence to guidelines on red blood cell transfusions in women having post-partum haemorrhage

    Research output: Contribution to journalJournal articleResearchpeer-review

View graph of relations

INTRODUCTION: In high-income countries the majority of pregnancies have a good outcome, and many adverse obstetric outcomes rarely occur. This makes demonstrating clinically relevant and statistically significant effects of new interventions a challenge. The objective of the study was to report incidences of important obstetric outcomes and to calculate sample sizes for tentative studies.

MATERIAL AND METHODS: The study was a registry-based study. Data were retrieved from the Danish Medical Birth Registry and included all deliveries in Denmark from 2008 to 2015. The total population included 465 919 deliveries. The study population comprised intended vaginal deliveries with a single fetus in cephalic presentation at term (n = 381 567). Incidences were reported for 20 outcomes considering the relevance for the patients and the severity of the outcomes. We calculated the sample sizes required in tentative obstetric studies to detect risk reductions of 25 and 50%, for tests at the 5% level, using a power of 80 and 90%. For the randomized controlled trials we calculated the sample size required for comparing two proportions with equal-sized groups. For the cohort study we calculated the sample size also required for two proportions but with unequal sized groups. Outcome measures for sample size calculation were neonatal mortality, Apgar score <7 at 5 minutes and emergency cesarean section.

RESULTS: The incidence of neonatal mortality, Apgar score <7 at 5 minutes and emergency cesarean section was 0.05, 0.58 and 10.5%, respectively. Using neonatal mortality as the outcome in a tentative randomized controlled trial with an expected risk reduction of 50% and power of 80%, our calculation showed a sample size of 195 036 deliveries. Using Apgar score <7 at 5 minutes or emergency cesarean section as the outcome, 16 254 and 818 deliveries, respectively, were required. In tentative cohort studies, the required sample sizes were larger due to the unequal proportion of exposed/non-exposed women.

CONCLUSIONS: Most adverse obstetric outcomes occur rarely; thus, very large sample sizes are required to achieve adequate statistical power in randomized controlled trials. Multicenter studies, international collaborations or alternative study designs to randomized controlled trials could be considered.

Original languageEnglish
JournalActa Obstetricia et Gynecologica Scandinavica
Volume99
Issue number1
Pages (from-to)34-41
Number of pages8
ISSN0001-6349
DOIs
Publication statusPublished - Jan 2020

    Research areas

  • Adult, Apgar Score, Cesarean Section/statistics & numerical data, Denmark/epidemiology, Female, Humans, Incidence, Infant, Infant Mortality, Infant, Newborn, Pregnancy, Pregnancy Outcome/epidemiology, Randomized Controlled Trials as Topic, Registries, Sample Size

ID: 60965349