Ical techniques to evaluate the extensional and viscoelastic properties of the cervical mucus samples. In addition, mucus permeability was directly visualized by the passage of fluorescent microbeads through mucus samples.Figure 2. Example time series of spinnbarkeit test at 2, 5, 10, 15, and 20 mm in low-risk and high-risk cervical mucus samples. Almost all high-risk samples could be stretched to at least 20 mm without breaking (exhibiting spinnbarkeit). In contrast, mucus from low-risk patients had an average break length of 13.862.4 mm. doi:10.1371/journal.pone.0069528.gMaterials and Methods Patient SelectionInternal Review Board (Tufts Medical Center) approval was obtained prior to the start of this pilot case-control study (IRB#9355). Written informed consent was obtained from all participants prior to enrollment. Patients at high-risk for preterm delivery were defined as: 18?0 years old with singleton pregnancies between the gestational ages of 20 weeks 0 days and 34 weeks and 0 days gestation who were admitted to a Title Loaded From File tertiary care facility with suspected preterm labor. For the purposes of this study, preterm labor was defined as documented cervical change (dilation and/or effacement) in the setting of regular uterine contractions and 2 cm or greater cervical dilation. Patients at high-risk for preterm birth were approached to participate after uterine contractions abated and no cervical exam was performed for 48 hours. Hence, no patient was in active labor and the high-risk patients in the study are more properly described as being in `arrested preterm labor.’ Exclusion criteria included significant maternal medical conditions predisposing the patient to pretermlabor (i.e. collagen disorder, systemic infection), a maternal history of smoking or drug abuse at any time, a history of abnormal pap smear or cervical procedure at any time, amniocentesis or chorionic villus sampling within four weeks of enrollment, placenta previa during the incident pregnancy, rupture of R generating global profiles of serum antibody specificities [7]. The feasibility of amniotic membranes or active vaginal bleeding at the time of sample collection, a documented vaginal infection (yeast, chlamydia, trichomoniasis, gonorrhea, bacterial vaginosis) or urinary tract infection within 6 months, intra-abdominal surgery during the incident pregnancy and a pelvic exam, intercourse or antibiotic use within 48 hours of sample collection. High-risk patients were compared to gestational age-matched control subjects (1:1) who were not experiencing preterm labor. Low-risk control subjects were recruited from the antepartum service or the outpatient clinic. Recruitment occurred between February 1st 2011 and September 1st 2012. Guidelines for the reporting of observational studies in epidemiology (STROBE) were followed [27].Cervical Mucus Sample CollectionCervical mucus samples were obtained by sterile speculum exam using a Cooper Surgical Endocervical Curette with a 12cc Vacu-Lok Syringe placed at the external cervical os. Cervical mucus samples were used immediately or snap frozen in liquid nitrogen and stored at 280uCelsius. Patient samples were deidentified and data was stored in a password protected database. Due to the difficulty of extracting cervical mucus, we could obtain only relatively small sample volumes (approximately 200 mL). This volume was not sufficient to conduct each of the presented assays. Hence, the number of mucus samples that were used per assay was lower than the number of enrolled participants.Extensibility Measurement and Shea.Ical techniques to evaluate the extensional and viscoelastic properties of the cervical mucus samples. In addition, mucus permeability was directly visualized by the passage of fluorescent microbeads through mucus samples.Figure 2. Example time series of spinnbarkeit test at 2, 5, 10, 15, and 20 mm in low-risk and high-risk cervical mucus samples. Almost all high-risk samples could be stretched to at least 20 mm without breaking (exhibiting spinnbarkeit). In contrast, mucus from low-risk patients had an average break length of 13.862.4 mm. doi:10.1371/journal.pone.0069528.gMaterials and Methods Patient SelectionInternal Review Board (Tufts Medical Center) approval was obtained prior to the start of this pilot case-control study (IRB#9355). Written informed consent was obtained from all participants prior to enrollment. Patients at high-risk for preterm delivery were defined as: 18?0 years old with singleton pregnancies between the gestational ages of 20 weeks 0 days and 34 weeks and 0 days gestation who were admitted to a tertiary care facility with suspected preterm labor. For the purposes of this study, preterm labor was defined as documented cervical change (dilation and/or effacement) in the setting of regular uterine contractions and 2 cm or greater cervical dilation. Patients at high-risk for preterm birth were approached to participate after uterine contractions abated and no cervical exam was performed for 48 hours. Hence, no patient was in active labor and the high-risk patients in the study are more properly described as being in `arrested preterm labor.’ Exclusion criteria included significant maternal medical conditions predisposing the patient to pretermlabor (i.e. collagen disorder, systemic infection), a maternal history of smoking or drug abuse at any time, a history of abnormal pap smear or cervical procedure at any time, amniocentesis or chorionic villus sampling within four weeks of enrollment, placenta previa during the incident pregnancy, rupture of amniotic membranes or active vaginal bleeding at the time of sample collection, a documented vaginal infection (yeast, chlamydia, trichomoniasis, gonorrhea, bacterial vaginosis) or urinary tract infection within 6 months, intra-abdominal surgery during the incident pregnancy and a pelvic exam, intercourse or antibiotic use within 48 hours of sample collection. High-risk patients were compared to gestational age-matched control subjects (1:1) who were not experiencing preterm labor. Low-risk control subjects were recruited from the antepartum service or the outpatient clinic. Recruitment occurred between February 1st 2011 and September 1st 2012. Guidelines for the reporting of observational studies in epidemiology (STROBE) were followed [27].Cervical Mucus Sample CollectionCervical mucus samples were obtained by sterile speculum exam using a Cooper Surgical Endocervical Curette with a 12cc Vacu-Lok Syringe placed at the external cervical os. Cervical mucus samples were used immediately or snap frozen in liquid nitrogen and stored at 280uCelsius. Patient samples were deidentified and data was stored in a password protected database. Due to the difficulty of extracting cervical mucus, we could obtain only relatively small sample volumes (approximately 200 mL). This volume was not sufficient to conduct each of the presented assays. Hence, the number of mucus samples that were used per assay was lower than the number of enrolled participants.Extensibility Measurement and Shea.
