Prevalence of Preterm Labor in the United States
OBJECTIVE
•Preterm birth (PTB) is a leading cause of maternal and neonatal morbidity and mortality; PTB accounts for ~10.5% of all live births in
the United States (US).
•Preterm labor (PTL), which is diagnosed based on clinical assessment of regular uterine contractions and cervical dilation and/or effacement,
is a predisposing risk factor in ~50% of all PTBs.1,2
•As PTB rates in the US vary year after year,3 the epidemiology of PTL will require continual study to advance scientific knowledge and the management of this condition.
•The goal of this epidemiologic study was to provide nationally representative contemporary estimates of the prevalence of PTL, overall and by weeks’ gestational age (wGA), in the US.
STUDY DESIGN & METHODS
•This study used a retrospective cohort study design.
•Hospital deliveries in the Premier Healthcare Database (PHD) at
≥23 wGA between Jan. 1, 2016, and Sept. 30, 2021, among patients
12-55 years old, were included.
•Exclusions: pregnancies that did not reach 23 wGA, had ≥3 fetuses or were terminated, and hospital deliveries with no or multiple
wGA-specific International Classification of Diseases, 10th revision
(ICD-10) codes.
•Sample characteristics were examined between all pregnancies with and without a diagnosis of PTL using descriptive statistics.
•The prevalence of PTL was estimated as:*
PTL Prevalence (overall) = # pregnancies with PTL diagnosis × 100,000
Total # of pregnancies in sample
PTL Prevalence (wGA) = # pregnancies with PTL diagnosis × 100,000
Total # of pregnancies by wGA
•The prevalence of PTL with preterm delivery in the same delivery hospitalization was also estimated using epidemiologic methods.
•Prevalence is reported as per 100,000 pregnancies.
•External validity was examined comparing the prevalence of PTB documented in the PHD with estimates reported by the US Centers for Disease Control and Prevention (CDC).3
* Hospital deliveries, diagnoses, and wGA were based on ICD-10 codes. PTL diagnoses for an individual patient documented prior to the hospital delivery were captured as a lookback to 20 wGA. For individuals with repeat pregnancies observed in the data, only the first pregnancy was evaluated.
RESULTS: PREVALENCE ESTIMATES AND SAMPLE CHARACTERISTICS
7,005 per 100,000
Pregnancies with a PTL diagnosis at some point
4,369 per 100,000
Pregnancies with a PTL diagnosis and PTB in the same delivery hospitalization
3,109 per 100,000
Pregnancies with a PTL diagnosis during a hospital admission prior to the admission for delivery
Relative to the cohort of pregnancies without any PTL diagnosis, the cohort of pregnancies
with a PTL diagnosis had a significantly higher prevalence of the following (all P<0.0001):
•Hispanics and Non-Hispanic Blacks
•Single/unknown marital status
•Smokers
•Medicaid and Medicare coverage at delivery
•Twin pregnancies
•Cesarean deliveries
•Comorbidities as measured by risk indices for severe maternal morbidity (SMM) and, separately, non-transfusion SMM4
RESULTS: BIRTHS BY GESTATIONAL AGE
PTB estimates in this study were consistent with US birth estimates in 2021, as reported by the US CDC3
Among all PTBs in this study, 217,484 (43.6%) had a PTL diagnosis during pregnancy
Among all term births in this study, 131,641 (2.9%) had a PTL diagnosis during pregnancy
STUDY LIMITATIONS
•The PHD is a population-based health network. The use of this nationally representative sample limits selection bias and has strong external validity, which was confirmed in a comparison with CDC-reported birth estimates.
DISCUSSION & CONCLUSION
•This study is the first to provide nationally representative estimates of
the prevalence of PTL in the US.
•Characterization of the epidemiology of PTL provides a significant contribution to our understanding of this maternal condition and can help inform the development of medical innovations for PTL.
•Future research will examine the epidemiologic burden of PTL by maternal age, race/ethnicity, and geographic region.
DISCLOSURE
•All authors provided intellectual contributions and approve this poster.
•Study funded by Organon.
REFERENCES
1.ACOG. Obstet Gynecol. 2016;128:e155-e164
2.ACOG. Obstet Gynecol. 2012;119:1308-1317
3.Osterman MJK, Hamilton BE, Martin JA, Driscoll AK, Valenzuela CP. Births: Final data for 2021. National Vital Statistics Reports; vol 72, no 1. Hyattsville, MD: National Center for Health Statistics. 2023. DOI:
https://dx.doi.org/10.15620/cdc:122047.
4.Leonard SA., et al. An Expanded Obstetric Comorbidity Scoring System for Predicting Severe Maternal Morbidity. Obstet Gynecol. 2020;136(3):440-449
ACKNOWLEDGEMENTS
Analytic support provided by Dominic Nunag of Medicus Economics,
and graphic support provided by SNELL Medical Communication, Inc.
