July 19, 2012 — Clinical characteristics are a poor predictor of spontaneous preterm birth (SPTB) in nulliparous women, according to the results of a new study. In addition, the trial suggests, the risk factors for SPTB with intact membranes (SPTB-IM) differ from the risk factors for SPTB after prelabor rupture of the membranes (SPTB-PPROM). This suggests that there are different pathophysiological pathways underlying these distinct phenotypes.
Gustaaf Albert Decker, MD, PhD, from the University of Adelaide's Robinson Institute in South Australia, and colleagues published the results of a multicenter international study in the July issue of PLoS ONE. The study included a prospective cohort of low-risk nulliparous pregnant women. Of the 3234 women included in the study, the researchers documented 156 cases of SPTB.
Smoking was more common in the SPTB-IM group (22.9% vs 10.6% in term births; P < .001). "Not feeling well" was also a risk factor for SPTB-IM, as was marijuana use before pregnancy.
The presence of mild hypertension was identified as an independent risk factor for SPTB-PPROM, with an odds ratio of 9.65 (95% confidence interval [CI], 2.5 - 37.1). Many of the independent risk factors associated with SPTB-PPROM, however, were difficult for the authors to explain. For example, longer time to conceive was associated with a small but significantly increased risk for SPTB-PPROM.
The study found that greater maternal height and waking up during the night both provided protection from SPTB-PPROM, but not SPTB-IM.
Decreased cervical length was the major risk factor that was comparable for both SPTB-IM (4% increased risk) and SPTB-PPROM (5% increased risk). Body mass index was the only other variable that was comparable in both types of SPTB. The minimal overlap in risk factors between SPTB-IM and SPTB-PPROM reinforces that SPTB is heterogeneous and that there are differences between SPTB at different gestational ages.
Previous studies have pointed to high-risk genetic polymorphisms, socioeconomic deprivation, smoking, obesity, and poverty-related stress and poor nutrition as key mediators in adverse pregnancy outcomes, including SPTB.
This study was funded by New Enterprise Research Fund, Foundation for Research Science and Technology; Health Research Council; the Evelyn Bond Fund, Auckland District Health Board Charitable Trust; and the Premier’s Science and Research Fund, South Australian Government. The authors have disclosed no relevant financial relationships.
PLoS ONE. 2012;7:e39154. Full text
Medscape Medical News © 2012 WebMD, LLC
Send comments and news tips to news@medscape.net.
Cite this: Risk Factors for 2 Types of Preterm Birth Vary Greatly - Medscape - Jul 19, 2012.
Comments