Abstract
BackgroundEarly pregnancy loss (unintended pregnancy loss before 20 completed weeks of gestation) is a common adverse pregnancy outcome, with previous evidence reporting incidence ranging from 10 to 30% of detected pregnancies. The objective of this systematic review and meta-analysis is to determine the incidence and range of early pregnancy loss in contemporary pregnant populations based on studies with good internal and external validity. Findings may be useful for clinical counseling in pre-conception and family planning settings and for people who experience early pregnancy loss.MethodsWe will search MEDLINE, EMBASE, and CINAHL databases using combinations of medical subject headings and keywords. Peer-reviewed, full-text original research articles that meet the following criteria will be included: (1) human study; (2) study designs: controlled clinical trials or observational studies with at least 100 pregnancies in the denominator, or systematic reviews of studies using these designs; (3) conducted in high-income countries; (4) reporting early pregnancy loss incidence, defined as unintended early pregnancy loss occurring prior to 20 weeks’ gestation expressed as the number of losses among all pregnancies in the study period; (5) among a contemporary (1990 or later) general population of pregnancies; and (6) published between January 1, 1990, and August 31, 2021. We will assess the quality of included studies according to the United States Preventive Services Task Force Criteria for Assessing Internal and External Validity of Individual Studies. If appropriate, based on methodological comparability across included studies, we will conduct meta-analyses using random effects models to estimate the pooled incidence of early pregnancy loss among all studies with both good internal and external validity, with meta-analyses stratified by study design type (survey-based or self-reported and medical record-based), by induced abortion restrictions (restricted vs. unrestricted), and by gestational age (first trimester only vs. all gestational ages before 20 weeks).DiscussionThis systematic review will synthesize existing evidence to calculate a current estimate of early pregnancy loss incidence and variability in reported incidence estimates in high-income settings. The findings of this review may inform updates to clinical counseling in pre-conception and family planning settings, as well as for patients experiencing early pregnancy loss.Systematic review registrationWe have registered this review with the International Prospective Register of Systematic Reviews (PROSPERO #226267).
Highlights
Pregnancy loss is a common adverse pregnancy outcome, with previous evidence reporting incidence ranging from 10 to 30% of detected pregnancies
Current clinical practice guidelines on early pregnancy loss diagnosis and management published by the American College of Obstetricians and Gynecologists (ACOG) and the UK’s National Institute for Health and Care Excellence (NICE) cite incidence estimates of 10% [4] and 20% [5], respectively [2, 6, 7]
These commonly cited estimates of early pregnancy loss incidence may not be applicable to clinical counseling in most settings
Summary
The design and implementation of this systematic review will adhere to the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMAP) 2015 statement [23]. Eligibility criteria Peer-reviewed, full-text original research articles that meet all of the following inclusion criteria will be included in this review: (1) human study; (2) study designs: controlled clinical trials or observational studies (prospective cohort, retrospective cohort, cross-sectional, chart review, survey) with at least 100 pregnancies in the denominator, or systematic reviews of studies using these designs; (3) conducted in high-income countries (as defined by the World Bank; “High-Income OECD Countries” [25]); (4) reporting early pregnancy loss incidence, defined as unintended early pregnancy loss occurring prior to 20 weeks’ gestation expressed as the number of losses identified in typical practice settings (i.e., not specific research settings) among all pregnancies in the study period; (5) among a contemporary (1990 or later) general population of pregnancies; (6) published between January 1, 1990, and August 31, 2021. We will conduct all meta-analyses using Stata 14.0
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