Maternal Whole Blood Gene Expression at 18 and 28 Weeks of Gestation Associated with Spontaneous Preterm Birth in Asymptomatic Women

Abstract

The heterogeneity of spontaneous preterm birth (SPTB) requires an interdisciplinary approach to determine potential predictive risk factors of early delivery. The aim of this study was to investigate maternal whole blood gene expression profiles associated with spontaneous preterm birth (SPTB, <37 weeks) in asymptomatic pregnant women. The study population was a matched subgroup of women (51 SPTBs, 114 term delivery controls) who participated in the All Our Babies community based cohort in Calgary (n = 1878). Maternal blood at 17-23 (sampling time point 1, T1) and 27-33 weeks of gestation (T2) were collected. Total RNA was extracted and microarray was performed on 326 samples (165 women). Univariate analyses determined significant clinical factors and differential gene expression associated with SPTB. Thirteen genes were validated using qRT-PCR. Three multivariate logistic models were constructed to identify gene expression at T1 (Model A), T2 (Model B), and gene expression fold change from T1 to T2 (Model C) associated with SPTB. All models were adjusted for clinical factors. Model C can predict SPTB with 65% sensitivity and 88% specificity in asymptomatic women after adjusting for history of abortion and anaemia (occurring before T2). Clinical data enhanced the sensitivity of the Models to predict SPTB. In conclusion, clinical factors and whole blood gene expression are associated with SPTB in asymptomatic women. An effective screening tool for SPTB during pregnancy would enable targeted preventive approaches and personalised antenatal care.

Fig 1. Parturition begins weeks before labour onset.

(A) Labour is an inflammatory process with elevated levels of maternal circulating leukocytes and increased leukocyte infiltration into the myometrium, decidua and cervix before and during labour. (B) Parturition is a long complex process that begins weeks before the onset of labour. The cervix gradually ripens and the myometrium switches from a quiescent to a contractile state. (C) In preterm birth, the cascade of events culminating in birth is transposed earlier in gestation. iNOS, induced nitric oxide synthase; IL8, interleukin 8; HA, hyaluronan; GAGs, glycosaminoglycans; T1, study samples collected at 17–23 weeks of gestation; T2, study samples collected at 27–33 weeks of gestation. Illustrations adapted from Word et al [18].

Fig 2. Flowchart outlining the recruitment, patient phenotyping and sample selection process for this study.

Fig 3

The area under receiver operator characteristic curves of Models A, B and C after ten five-fold cross-validation (CV) runs. These three multivariate models were constructed to identify gene expression associated with spontaneous preterm birth (SPTB) at 17–23 weeks (A; Model A) and 27–33 weeks (B; Model B); and gene expression fold change from 17–23 to 27–33 weeks of gestation associated with SPTB (C; Model C). Models with clinical factors are represented using solid lines; Models without clinical factors are represented using dotted lines. The rainbow bar on the right of each plot displays cut-off probabilities. The colour of the points along the average CV curve reflects its respective cut-off probability to obtain the desired sensitivity and specificity.