Testing for risk of preterm delivery

Predicting Preterm Labour: Current Status and Future Prospects

Preterm labour and birth are a major cause of perinatal morbidity and mortality. Despite modern advances in obstetric and neonatal management, the rate of preterm birth in the developed world is increasing. Yet even though numerous risk factors associated with preterm birth have been identified, the ability to accurately predict when labour will occur remains elusive, whether it is at a term or preterm gestation. In the latter case, this is likely due to the multifactorial aetiology of preterm labour wherein women may display different clinical presentations that lead to preterm birth. The discovery of novel biomarkers that could reliably identify women who will subsequently deliver preterm may allow for timely medical intervention and targeted therapeutic treatments aimed at improving maternal and fetal outcomes. Various body fluids including amniotic fluid, urine, saliva, blood (serum/plasma), and cervicovaginal fluid all provide a rich protein source of putative biochemical markers that may be causative or reflective of the various pathophysiological disorders of pregnancy, including preterm labour. This short review will highlight recent advances in the field of biomarker discovery and the utility of single and multiple biomarkers for the prediction of preterm birth in the absence of intra-amniotic infection.

Human cervicovaginal fluid biomarkers to predict term and preterm labor

Preterm birth (PTB; birth before 37 completed weeks of gestation) remains the major cause of neonatal morbidity and mortality. The current generation of biomarkers predictive of PTB have limited utility. In pregnancy, the human cervicovaginal fluid (CVF) proteome is a reflection of the local biochemical milieu and is influenced by the physical changes occurring in the vagina, cervix and adjacent overlying fetal membranes. Term and preterm labor (PTL) share common pathways of cervical ripening, myometrial activation and fetal membranes rupture leading to birth. We therefore hypothesize that CVF biomarkers predictive of labor may be similar in both the term and preterm labor setting. In this review, we summarize some of the existing published literature as well as our team's breadth of work utilizing the CVF for the discovery and validation of putative CVF biomarkers predictive of human labor. Our team established an efficient method for collecting serial CVF samples for optimal 2-dimensional gel electrophoresis resolution and analysis. We first embarked on CVF biomarker discovery for the prediction of spontaneous onset of term labor using 2D-electrophoresis and solution array multiple analyte profiling. 2D-electrophoretic analyses were subsequently performed on CVF samples associated with PTB. Several proteins have been successfully validated and demonstrate that these biomarkers are associated with term and PTL and may be predictive of both term and PTL. In addition, the measurement of these putative biomarkers was found to be robust to the influences of vaginal microflora and/or semen. The future development of a multiple biomarker bed-side test would help improve the prediction of PTB and the clinical management of patients.

Biomarker interactions are better predictors of spontaneous preterm birth

OBJECTIVE

The objective of this study was to assess the role of biomarker interactions as predictors of spontaneous preterm birth (PTB) using multifactor dimensionality reduction (MDR) analysis. With MDR, a nonparametric, unsupervised, model-free approach, we tested for biomarker interactions within maternal-fetal compartments in 2 racial groups: African Americans (AA) and Caucasians (C).

STUDY DESIGN

A total of 36 biomarkers from maternal plasma (MP), cord plasma (CP), and amniotic fluid (AF) were analyzed from 191 patients. The MDR combined attribute selection, construction, and classification to detect biomarker interactions that were assessed for generality and significance using 10× cross-validation and permutation testing. Selected significant interactive models were replicated with additional samples.

RESULTS

The interactive model containing interleukin (IL)-2, angiopoietin 2 (ANGPT-2), and IL-6 receptor was significant in AA MP. In AA CP, the IL-8 and tumor necrosis factor (TNF) receptor 1 model was significant. In AA AF, the ANGPT-2 and macrophage inflammatory protein 1 alpha model was significant. Replication of the AA MP model using 54 additional AA MP samples confirmed predictability of these biomarkers. In C AF, interaction was observed between ANGPT-2, monocyte chemotactic protein 3, and TNF-α, but no other interactions were significant in C.

CONCLUSIONS

Using MDR, we identified biomarker interactions that are predictors of PTB even in the absence of a main effect with a single biomarker.

First-trimester vaginal bleeding and complications later in pregnancy

OBJECTIVE

To evaluate the association of first-trimester bleeding without miscarriage and complications later in the first pregnancy as well as in the next pregnancy.

METHODS

In a retrospective, registry-based cohort study, we identified women delivering in Denmark from 1978 to 2007 with a first singleton pregnancy (n=782,287) and first and second singleton pregnancies (n=536,419). First-trimester bleeding is defined as vaginal bleeding before 12 full weeks of gestation. We employed multivariate logistic regression with adjustment for maternal age and calendar year.

RESULTS

First-trimester bleeding increased the risk of delivery in weeks 32-36 from 3.6% to 6.1% (odds ratio [OR], 1.65; 95% confidence interval [CI], 1.57-1.77) and in weeks 28-31 from 0.3% to 0.9% (OR 2.98; 95% CI 2.50-3.54) and increased the risk of placental abruption from 1.0% to 1.4% (OR 1.48; 95% CI 1.30-1.68). First-trimester bleeding in the first pregnancy increased the risk of recurrence in the second pregnancy from 2.2% to 8.2% (OR 4.05; 95% CI 3.78-4.34), preterm delivery from 2.7% to 4.8% (OR 1.83; 95% CI 1.67-2.00), and placental abruption from 0.9% to 1.0% (OR 1.29; 95% CI 1.07-1.56) in the second pregnancy.

CONCLUSION

Women with first-trimester bleeding in the first pregnancy have an increased risk of complications later in the first pregnancy and of recurrence of first-trimester bleeding and other complications in the second pregnancy.

Geographic ancestry and markers of preterm birth

Several biomarkers associated with spontaneous preterm birth (PTB) have been discovered over the last decade. Many of these markers, such as cytokines, are associated with infection and inflammation. As such, these biomarkers represent biologically plausible candidates for assessing those at risk of PTB. However, in the early association studies of biomarker-pregnancy outcome, the geographic ancestry of subjects was not considered. Based on more recent data, it is becoming increasingly evident that these biomarkers, and a universal approach that uses a single biomarker, fail to provide adequate assessment of risk in all subjects. Rather, recent data support the conclusion that some markers associate in subjects of African descent and another nonoverlapping set associates in subjects of European descent. These data indicate that diagnostic or predictive tests will have to use different biomarkers for different sets of subjects. If this is true, it poses severe restrictions on how to predict outcome or perform tests of association, and may make it impossible to determine risk or provide proper intervention. An alternative is presented that, although not yet proven, may make it possible to use a common set of biomarkers and their relationships to assess risk.

Evidence of placental haemorrhage and preterm delivery

OBJECTIVE

To evaluate evidence of placental haemorrhage (PH) obtained through maternal interviews, patient charts and placental pathology examinations as potential indicators of a 'bleeding pathway' to preterm delivery (PTD).

DESIGN

Prospective cohort.

SETTING

Fifty-two clinics in five communities in Michigan, USA (1998-2004).

POPULATION

A subset (n = 996) of cohort participants with complete placental pathology data.

METHODS

First-trimester bleeding and placental abruption were ascertained by mid-trimester interviews and chart review, respectively. Disc-impacting blood clot was defined as a gross placental examination finding of a blood clot impacting adjacent tissue. Microscopic haemorrhage was defined as 'high' (top quintile) scores on an aggregate measure of placental pathology findings suggestive of atypical maternal vessel haemorrhage. These four PH indicators were compared with one another and with risk of PTD assessed by logistic regression analyses.

MAIN OUTCOME MEASURES

Preterm delivery and PTD subtypes (i.e. <35 weeks, 35-36 weeks; spontaneous, medically indicated) compared with term deliveries.

RESULTS

Placental abruption cases had 2.3-fold to 5.5-fold increased odds of the other three PH indicators. Disc-impacting blood clots and microscopic haemorrhage were associated with one another (odds ratio [OR] = 4.6), but not with first-trimester bleeding. In a multivariable model that included all four PH indicators and confounders, risk of PTD < 35 weeks was elevated with first-trimester bleeding (OR = 1.9 [1.0, 3.4]), placental abruption (OR = 5.2 [1.7, 16.2]), disc-impacting blood clots (OR = 2.3 [1.0, 5.0]) and microscopic haemorrhage (OR = 2.4 [1.4, 4.2]).

CONCLUSIONS

Multiple clinical and subclinical PH indicators are associated with PTD, particularly early PTD.

Salivary progesterone and estriol among pregnant women treated with 17-alpha-hydroxyprogesterone caproate or placebo

OBJECTIVE

The objectives of the study was to determine whether salivary progesterone (P) or estriol (E3) concentration at 16-20 weeks' gestation predicts preterm birth or the response to 17alpha-hydroxyprogesterone caproate (17OHPC) and whether 17OHPC treatment affected the trajectory of salivary P and E3 as pregnancy progressed.

STUDY DESIGN

This was a secondary analysis of a clinical trial of 17OHPC to prevent preterm birth. Baseline saliva was assayed for P and E3. Weekly salivary samples were obtained from 40 women who received 17OHPC and 40 who received placebo in a multicenter randomized trial of 17OHPC to prevent recurrent preterm delivery.

RESULTS

Both low and high baseline saliva P and E3 were associated with a slightly increased risk of preterm birth. However, 17OHPC prevented preterm birth comparably, regardless of baseline salivary hormone concentrations. 17OHPC did not alter the trajectory of salivary P over pregnancy, but it significantly blunted the rise in salivary E3 as well as the rise in the E3/P ratio.

CONCLUSION

17OHPC flattened the trajectory of E3 in the second half of pregnancy, suggesting that the drug influences the fetoplacental unit.

Multidimensional proteomics analysis of amniotic fluid to provide insight into the mechanisms of idiopathic preterm birth

Background

Though recent advancement in proteomics has provided a novel perspective on several distinct pathogenetic mechanisms leading to preterm birth (inflammation, bleeding), the etiology of most preterm births still remains elusive. We conducted a multidimensional proteomic analysis of the amniotic fluid to identify pathways related to preterm birth in the absence of inflammation or bleeding.

Methodology/Principal Findings

A proteomic fingerprint was generated from fresh amniotic fluid using surface-enhanced laser desorbtion ionization time of flight (SELDI-TOF) mass spectrometry in a total of 286 consecutive samples retrieved from women who presented with signs or symptoms of preterm labor or preterm premature rupture of the membranes. Inflammation and/or bleeding proteomic patterns were detected in 32% (92/286) of the SELDI tracings. In the remaining tracings, a hierarchical algorithm was applied based on descriptors quantifying similarity/dissimilarity among proteomic fingerprints. This allowed identification of a novel profile (Q-profile) based on the presence of 5 SELDI peaks in the 10–12.5 kDa mass area. Women displaying the Q-profile (mean±SD, gestational age: 25±4 weeks, n = 40) were more likely to deliver preterm despite expectant management in the context of intact membranes and normal amniotic fluid clinical results. Utilizing identification-centered proteomics techniques (fluorescence two-dimensional differential gel electrophoresis, robotic tryptic digestion and mass spectrometry) coupled with Protein ANalysis THrough Evolutionary Relationships (PANTHER) ontological classifications, we determined that in amniotic fluids with Q-profile the differentially expressed proteins are primarily involved in non-inflammatory biological processes such as protein metabolism, signal transduction and transport.

Conclusion/Significance

Proteomic profiling of amniotic fluid coupled with non-hierarchical bioinformatics algorithms identified a subgroup of patients at risk for preterm birth in the absence of intra-amniotic inflammation or bleeding, suggesting a novel pathogenetic pathway leading to preterm birth. The altered proteins may offer opportunities for therapeutical intervention and future drug development to prevent prematurity.

Effect of a cholesterol-lowering diet during pregnancy on maternal and fetal Doppler velocimetry: the CARRDIP study

OBJECTIVE

The purpose of this study was to evaluate the effect of a low-cholesterol low-saturated fat diet on Doppler indices in the fetus and mother.

STUDY DESIGN

Two hundred ninety nonsmoking white women, aged 21-38 years, without previous pregnancy complications and carrying a single fetus were assigned randomly to continue their usual diet (control subjects; n = 149) or to adopt a low-cholesterol low-saturated fat diet (intervention group; n = 141) from gestational week 17-20 to birth. Doppler velocimetry of the umbilical artery and both uterine arteries were assessed at gestational weeks 24, 30, and 36.

RESULTS

The physiologic gestational decrease in umbilical artery pulsatility index (PI) from week 24-30 was more pronounced in the intervention group, compared with the control group, with median values (interquartile range) of -0.17 (-0.29, -0.06) and -0.11 (-0.25, 0.01), respectively (P = .048). Assignment to the intervention diet did not influence the changes in mean PI value of the 2 uterine arteries (P = .3). The change in umbilical artery PI and mean PI value of the uterine arteries between weeks 24 and 36 were not significantly different between the 2 groups (P = 1.0 and .2 respectively).

CONCLUSION

Our study shows that a cholesterol-lowering diet during pregnancy may modify fetoplacental circulation in mid pregnancy.

Preconception care between pregnancies: the content of internatal care

For more than two decades, prenatal care has been a cornerstone of our nation's strategy for improving pregnancy outcomes. In recent years, however, a growing recognition of the limits of prenatal care and the importance of maternal health before pregnancy has drawn increasing attention to preconception and internatal care. Internatal care refers to a package of healthcare and ancillary services provided to a woman and her family from the birth of one child to the birth of her next child. For healthy mothers, internatal care offers an opportunity for wellness promotion between pregnancies. For high-risk mothers, internatal care provides strategies for risk reduction before their next pregnancy. In this paper we begin to define the contents of internatal care. The core components of internatal care consist of risk assessment, health promotion, clinical and psychosocial interventions. We identified several priority areas, such as FINDS (family violence, infections, nutrition, depression, and stress) for risk assessment or BBEEFF (breastfeeding, back-to-sleep, exercise, exposures, family planning and folate) for health promotion. Women with chronic health conditions such as hypertension, diabetes, or weight problems should receive on-going care per clinical guidelines for their evaluation, treatment, and follow-up during the internatal period. For women with prior adverse outcomes such as preterm delivery, we propose an internatal care model based on known etiologic pathways, with the goal of preventing recurrence by addressing these biobehavioral pathways prior to the next pregnancy. We suggest enhancing service integration for women and families, including possibly care coordination and home visitation for selected high-risk women. The primary aim of this paper is to start a dialogue on the content of internatal care.

Biochemistry testing associated with pregnancy and the newborn period -- a lot has changed since you were a baby!

Everyone has been a newborn, and everyone's mother has been pregnant. Despite the commonality of these events, medical care and the clinical chemistry laboratory's role in it have changed remarkably over the last 50 years. This review is a historical overview of clinical chemistry testing that is related to pregnancy and the newborn period.