ChatGPT: a pioneering approach to complex prenatal differential diagnosis.

This commentary examines how ChatGPT can assist healthcare teams in the prenatal diagnosis of rare and complex cases by creating a differential diagnoses based on deidentified clinical findings, while also acknowledging its limitations.

Blood type and postpartum hemorrhage by mode of delivery: A retrospective cohort study.

OBJECTIVE: To assess the relationship between postpartum hemorrhage and ABO blood type for vaginal delivery and cesarean delivery. STUDY DESIGN: This is a retrospective cohort study of data abstracted from the PeriBank database regarding demographics and delivery outcomes. All live singleton deliveries from January 2011 until March 2018 were included in this study. Exclusion criteria were sickle cell disease and multiple gestations. Analyses were conducted separately for cesarean delivery and vaginal delivery. Quantitative variables were analyzed with analysis of variance testing and categorical variables with chi square testing. Significant demographic differences between groups were controlled for using multivariate logistical regression. The primary outcome was the rate of postpartum hemorrhage by blood type (A, B, AB, and O), defined as blood loss >500 mL in vaginal delivery and >1000 mL in cesarean delivery. 43,437 patients were screened and 32,023 women met inclusion criteria (22,484 vaginal deliveries (70.2%) and 9539 cesarean deliveries (29.8%)). RESULTS: In the vaginal delivery group there were differences in age, parity, race, use of regional anesthesia, rate of induction of labor, and thrombocytopenia between blood types. In the cesarean delivery group, age, parity, and race were significantly different between blood types. There was no observed difference in the rate of postpartum hemorrhage by blood type for those who delivered via vaginal delivery when controlling for demographic differences (p = 0.2). In the cesarean delivery group, there was a significantly higher rate of postpartum hemorrhage in women with type O blood (5.2% type O vs 3.8% type A vs 4.4% type B vs 4.2% type AB, p = 0.035), including when controlling for demographic differences (p = 0.02). In both vaginal and cesarean delivery groups, there was no difference in rates of any of the secondary outcomes, including blood transfusion, hysterectomy, intrapartum dilation and curettage, and intensive care unit admission. CONCLUSION: Although this study found no statistically significant difference in clinical outcomes between blood types, type O blood may be an additional risk factor to consider for postpartum hemorrhage at the time of cesarean delivery.

Pregnancy and Lactation in a 67-Year-Old Elderly Gravida following Donor Oocyte In Vitro Fertilization.

There is limited data on the anticipated perinatal course among gravidae in their sixth and seventh decades. Our objective was to describe the relatively uncomplicated prenatal, intrapartum, and postpartum course of a 67-year-old essential primigravida. Briefly, our patient conceived a singleton pregnancy via IVF with donor oocytes, then presented at 13 6/7 weeks of gestation to initiate prenatal care. Her medical history was significant for chronic hypertension, hyperlipidemia, and obesity. Her cardiac function was monitored throughout pregnancy, and she delivered at 36 1/7 weeks by cesarean for a decline in left ventricular function with mitral regurgitation. Her intrapartum and postpartum course was uncomplicated, and she was able to successfully breastfeed for six months and resume prepregnancy activity. For comparison, we analyzed deliveries among gravidae > 45 years of age from our institutional obstetrical database (2011-2018). This case represents the eldest gravidae identified in the literature and illustrates the potential for a relatively uncomplicated perinatal course with successful lactation. This case may enable other providers to counsel elderly patients on anticipated outcomes inclusive of ability to breastfeed.

Severe acute respiratory distress syndrome in coronavirus disease 2019-infected pregnancy: obstetric and intensive care considerations.

Since the emergence of a novel coronavirus (severe acute respiratory syndrome coronavirus 2) in Wuhan, China, at the end of December 2019, coronavirus disease 2019 has been associated with severe morbidity and mortality and has left world governments, healthcare systems, and providers caring for vulnerable populations, such as pregnant women, wrestling with the optimal management strategy. Unique physiologic and ethical considerations negate a one-size-fits-all approach when caring for critically ill pregnant women with coronavirus disease 2019, and few resources exist to guide the multidisciplinary team through decisions regarding optimal maternal-fetal surveillance, intensive care procedures, and delivery timing. We present a case of rapid clinical decompensation and development of severe acute respiratory distress syndrome in a woman at 31 weeks' gestation to highlight these unique considerations and present an algorithmic approach to the diagnosis and management of the disease.

Clinical course of severe and critical coronavirus disease 2019 in hospitalized pregnancies: a United States cohort study.

Background: The coronavirus disease 2019 pandemic has had an impact on healthcare systems around the world with 3 million people contracting the disease and 208,000 cases resulting in death as of this writing. Information regarding coronavirus infection in pregnancy is still limited. Objective: This study aimed to describe the clinical course of severe and critical coronavirus disease 2019 in hospitalized pregnant women with positive laboratory testing for severe acute respiratory syndrome coronavirus 2. Study Design: This is a cohort study of pregnant women with severe or critical coronavirus disease 2019 hospitalized at 12 US institutions between March 5, 2020, and April 20, 2020. Severe disease was defined according to published criteria as patient-reported dyspnea, respiratory rate >30 per minute, blood oxygen saturation ≤93% on room air, ratio of partial pressure of arterial oxygen to the fraction of inspired oxygen <300 mm Hg, or lung infiltrates >50% within 24-48 hours on chest imaging. Critical disease was defined as respiratory failure, septic shock, or multiple organ dysfunction or failure. Women were excluded from the study if they had presumed coronavirus disease 2019, but laboratory testing was negative. The primary outcome was median duration from hospital admission to discharge. Secondary outcomes included need for supplemental oxygen, intubation, cardiomyopathy, cardiac arrest, death, and timing of delivery. The clinical courses are described by the median disease day on which these outcomes occurred after the onset of symptoms. Treatment and neonatal outcomes are also reported. Results: Of 64 hospitalized pregnant women with coronavirus disease 2019, 44 (69%) had severe disease, and 20 (31%) had critical disease. The following preexisting comorbidities were observed: 25% had a pulmonary condition, 17% had cardiac disease, and the mean body mass index was 34 kg/m2. Gestational age was at a mean of 29±6 weeks at symptom onset and a mean of 30±6 weeks at hospital admission, with a median disease day 7 since first symptoms. Most women (81%) were treated with hydroxychloroquine; 7% of women with severe disease and 65% of women with critical disease received remdesivir. All women with critical disease received either prophylactic or therapeutic anticoagulation during their admission. The median duration of hospital stay was 6 days (6 days [severe group] and 10.5 days [critical group]; P=.01). Intubation was usually performed around day 9 on patients who required it, and peak respiratory support for women with severe disease was performed on day 8. In women with critical disease, prone positioning was required in 20% of cases, the rate of acute respiratory distress syndrome was 70%, and reintubation was necessary in 20%. There was 1 case of maternal cardiac arrest, but there were no cases of cardiomyopathy or maternal death. Thirty-two of 64 (50%) women with coronavirus disease 2019 in this cohort delivered during their hospitalization (34% [severe group] and 85% [critical group]). Furthermore, 15 of 17 (88%) pregnant women with critical coronavirus disease 2019 delivered preterm during their disease course, with 16 of 17 (94%) pregnant women giving birth through cesarean delivery; overall, 15 of 20 (75%) women with critical disease delivered preterm. There were no stillbirths or neonatal deaths or cases of vertical transmission. Conclusion: In pregnant women with severe or critical coronavirus disease 2019, admission into the hospital typically occurred about 7 days after symptom onset, and the duration of hospitalization was 6 days (6 [severe group] vs 12 [critical group]). Women with critical disease had a high rate of acute respiratory distress syndrome, and there was 1 case of cardiac arrest, but there were no cases of cardiomyopathy or maternal mortality. Hospitalization of pregnant women with severe or critical coronavirus disease 2019 resulted in delivery during the clinical course of the disease in 50% of this cohort, usually in the third trimester. There were no perinatal deaths in this cohort.

Second-trimester cervical length and outcomes of induction of labor at term.

OBJECTIVE: To evaluate whether second-trimester cervical length (CL) is associated with induction of labor (IOL) outcomes. METHODS: Retrospective cohort study of nulliparous singletons undergoing CL screening at 18 0/7-23 6/7 weeks from 1/1/2012 to 12/31/2013. Women induced at term (≥37 weeks) were included. Primary outcome was vaginal delivery (VD) within 24 h. The effect of CL on outcomes was assessed by incidence across CL quartiles and a receiver operating characteristics (ROC) curve. Odds ratios (OR) were adjusted (aOR) for confounders. RESULTS: Two-hundred-and-sixty-eight women were included. Aside from a difference in incidence of prior cervical surgery between CL quartiles (p <. 02), other characteristics were similar. Ninety-two women (35%) had a VD within 24 h (versus a CD or VD >24 h). A longer a CL was associated with a decreased likelihood of a VD within 24 h with aORs of the third and fourth quartiles of 0.35 (0.16-0.75) and 0.43 (0.21-0.90), respectively, compared to the first quartile. A CL >40 mm was predictive of not having a VD within 24 h with a sensitivity of 56%, specificity of 58% and a positive predictive value of 72%. CONCLUSION: A second-trimester CL >40 mm is associated with a decreased likelihood of VD within 24 h in an IOL.

Overview of Cervical Insufficiency: Diagnosis, Etiologies, and Risk Factors.

The diagnosis of cervical insufficiency can be made in women with or without prior pregnancy losses. Cervical insufficiency has been defined by transvaginal ultrasound cervical length <25 mm before 24 weeks in women with prior pregnancy losses or preterm births at 14 to 36 weeks, or by cervical changes detected on physical examination before 24 weeks of gestation.

Cerclage: Indications and Patient Counseling.

Cervical cerclage is a surgical procedure to prevent preterm birth. There are currently 3 main indications, based on either history, ultrasound, or physical exam changes.

Second trimester cervical length and prolonged pregnancy (.).

OBJECTIVE: To determine whether second trimester transvaginal ultrasound cervical length (CL) is associated with prolonged pregnancy (≥41 0/7 weeks) in nulliparous women who reach term (≥37 weeks) with a planned vaginal delivery. METHODS: Retrospective cohort of nulliparous singletons 18 0/7-23 6/7 weeks gestation undergoing CL screening from 1/1/12 to 12/31/13. Women who delivered at term with spontaneous labor or reached 41 weeks were included. Primary outcome was incidence of prolonged pregnancy. Risk of prolonged pregnancy was assessed by CL quartile using odds ratio, adjusted for confounders (aOR) and a receiver operating characteristic (ROC) curve. RESULTS: 722 women were included, among them 171 (24%) had a prolonged pregnancy. There was a significant difference in BMI and race across CL quartiles. The aOR of having a prolonged pregnancy with CL in quartiles 2, 3, and 4 versus quartile 1 were 2.14(1.27-3.62), 2.72(1.59-4.65), and 1.69(1.02-3.03), respectively. CL ≥ 37 mm (beyond first quartile) was associated with a two-fold increased risk of prolonged pregnancy versus CL < 37 mm, (27% vs 15%, p < 0.01, aOR 2.17 (1.38-3.41)). ROC curve did not identify a CL cutoff that was predictive of prolonged pregnancy (AUC 0.544, p = 0.079). CONCLUSIONS: Although a longer second trimester CL is associated with an increased risk for prolonged pregnancy, it is not predictive.

Pre-pregnancy body mass index (BMI) and cerclage success.

OBJECTIVE: This study was performed to evaluate the effect of pre-pregnancy body mass index (BMI) on the success of cerclage. MATERIALS AND METHODS: A retrospective cohort study of women who had a history-indicated (HIC) or ultrasound-indicated cerclage (UIC) placed between 1994 and 2011. Based on pre-pregnancy BMI (World Health Organization criteria), three cohorts were defined: normal/overweight (BMI: 20.0-29.9 kg/m(2)), obese class I/II (BMI: 30.0-39.9 kg/m(2)) and obese class III (BMI ≥ 40.0 kg/m(2)). The primary outcome was spontaneous preterm birth (sPTB) <35 weeks. The secondary outcomes included but were not limited to gestational age of delivery, sPTB <37, <32 and <28 weeks, preterm premature rupture of membranes and birth weight. RESULTS: 375 women were included for analysis. Demographics were similar in the three BMI categories, except black race (p = 0.01). The rates of sPTB <35 weeks were similar between each cohort: 24.3%, 23.0% and 27.7%, respectively (p = 0.81). BMI was not a predictor of any of the secondary outcomes. A HIC was placed in 47.2% and an UIC was placed in 52.8% women. Both unadjusted and adjusted analysis showed no significant difference in sPTB <35 weeks between BMI categories overall or by cerclage type (HIC or UIC). CONCLUSIONS: Pre-pregnancy BMI is not a significant predictor of sPTB <35 weeks in women with HIC or UIC.

Pessary versus cerclage versus expectant management for cervical dilation with visible membranes in the second trimester.

OBJECTIVE: We evaluated pessary for dilated cervix and exposed membranes for prolonging pregnancy compared to cerclage or expectant management. METHODS: Multicenter retrospective cohort study of women, 15-24 weeks, singleton pregnancies, dilated cervix ≥2 cm and exposed membranes. Women received pessary, cerclage or expectant management. Primary outcome was gestational age (GA) at delivery. Secondary outcomes were time until delivery, preterm premature rupture of membranes (PPROM) and neonatal survival. RESULTS: About 112 women met study criteria; 9 - pessary, 85 - cerclage and 18 - expectant management. Mean GA at delivery was 22.9 ± 4.5 weeks with pessary, 29.2 ± 7.5 weeks with cerclage and 25.6 ± 6.7 weeks with expectant management (p = 0.015). Time until delivery was 16.1 ± 18.9 days in the pessary group, 61.7 ± 48.2 days in the cerclage group and 26.8 ± 33.4 days in the expectant group (p < 0.001). PPROM occurred less frequently and neonatal survival increased in women with cerclage. There was a significant difference in all the perinatal outcomes with cerclage compared with either pessary or expectant management. CONCLUSIONS: Perinatal outcomes with pessary were not superior to expectant management in women with dilated cervix with exposed membranes in the second trimester in this small retrospective cohort.

Prior Ultrasound-Indicated Cerclage: Comparison of Cervical Length Screening or History-Indicated Cerclage in the Next Pregnancy.

OBJECTIVE: To evaluate outcomes of women with prior ultrasound-indicated cerclage, who in their subsequent pregnancy were either followed by transvaginal ultrasound cervical length screening or received a planned history-indicated cerclage. METHODS: Multicenter cohort study of singleton gestations with a prior ultrasound-indicated cerclage performed from 1994 to 2014. We evaluated three pregnancies in the study participants: first pregnancy with prior spontaneous preterm birth at less than 37 weeks of gestation; second pregnancy with ultrasound-indicated cerclage for cervical length 25 mm or less; and the third index pregnancy managed with either transvaginal ultrasound cervical length screening with ultrasound-indicated cerclage for cervical length 25 mm or less or planned history-indicated cerclage. The primary outcome was incidence of spontaneous preterm birth at less than 37 weeks of gestation. We planned a subgroup analysis for women who delivered at less than 32 weeks of gestation compared with 32 weeks of gestation or greater in their prior ultrasound-indicated cerclage pregnancy. RESULTS: Of 102 singleton gestations included, 38 (37.3%) were followed with transvaginal ultrasound cervical length screening and 64 (62.7%) underwent history-indicated cerclage. Of 38 women in the transvaginal ultrasound group, 18 (47.4%) underwent ultrasound-indicated cerclage for cervical length 25 mm or less. After adjusting for confounders, the rate of spontaneous preterm birth at less than 37 weeks of gestation was similar between transvaginal ultrasound cervical length screening and history-indicated cerclage groups (36.8% compared with 43.8%; adjusted odds ratio 0.77, 95% confidence interval 0.47-1.45). Secondary outcomes were also similar in both groups. All women (n=7) who delivered at less than 32 weeks of gestation in their prior pregnancy and subsequently had transvaginal ultrasound screening received ultrasound-indicated cerclage in the index pregnancy compared with only 35.5% of women who delivered at 32 weeks of gestation or greater in their prior pregnancy. CONCLUSION: Women with prior ultrasound-indicated cerclage have similar outcomes if they receive either transvaginal ultrasound cervical length screening with ultrasound-indicated cerclage for cervical length 25 mm or less or planned history-indicated cerclage in the subsequent pregnancy. Less than 50% of the transvaginal ultrasound cervical length screening group require a repeat ultrasound-indicated cerclage in the subsequent pregnancy. LEVEL OF EVIDENCE: II.

Trends in cerclage use.

INTRODUCTION: The indications of placement of cerclage have recently changed, and so it is important to evaluate how many women are undergoing this procedure. With the recent completion of clinical trials, it is plausible that obstetricians and perinatologists may have become more selective in terms of the best candidates for cerclage. MATERIAL AND METHODS: We conducted a retrospective cohort study of women who underwent cerclage for prevention of preterm birth in the Division of Maternal and Fetal Medicine of Thomas Jefferson University Hospital (Philadelphia, USA) over a 16-year period, from 1998 to 2013. We included women with singleton gestations who had a history-indicated (HIC) or ultrasound-indicated cerclage (UIC). Physical examination-indicated cerclage and transabdominal cerclage were excluded. We planned to compare data before and after 2005. RESULTS: From 1998 to 2013, there were 33 353 deliveries, of which 16 871 occurred from 1998 to 2005 and 16 482 from 2006 to 2013. Of all deliveries, 328 women (1.0%) received HIC or UIC, and were therefore included in the analysis. Between 1998-2005 and 2006-2013 there were significant decreases in the overall rate of cerclage (1.4% to 0.6%; p < 0.001), as well as the rate of HIC (0.8% to 0.2%; p < 0.001) and UIC (0.6% to 0.3%; p < 0.001). CONCLUSIONS: During the last 16 years, the overall rate of HIC and UIC cerclage at Thomas Jefferson University Hospital significantly declined from 1.4% to 0.6%; significant decreases were seen for both HIC and UIC. The reason for the lower rate of cerclages may be the recently published evidence.

Short cervical length dilemma.

Preterm birth (PTB) is a leading cause of neonatal morbidity and mortality. With research efforts, the rate of PTB decreased to 11.4% in 2013. Transvaginal ultrasound (TVU) cervical length (CL) screening predicts PTB. In asymptomatic singletons without prior spontaneous PTB (sPTB), TVU CL screening should be done. If the cervix is 20 mm or less, vaginal progesterone is indicated. In asymptomatic singletons with prior sPTB, serial CL screening is indicated. In multiple gestations, routine cervical screening is not indicated. In symptomatic women with preterm labor, TVU CL screening and fetal fibronectin testing is recommended.

Vaginal progesterone for maintenance tocolysis: a systematic review and metaanalysis of randomized trials.

OBJECTIVE: We sought to evaluate the efficacy of maintenance tocolysis with vaginal progesterone compared to control (placebo or no treatment) in singleton gestations with arrested preterm labor (PTL) in a metaanalysis of randomized controlled trials. STUDY DESIGN: Searches were performed in MEDLINE, OVID, Scopus, ClinicalTrials.gov, and the Cochrane Central Register of Controlled Trials with the use of a combination of key words and text words related to "progesterone," "tocolysis," and "preterm labor" from 1966 through November 2014. We included all randomized trials of singleton gestations that had arrested PTL and then were randomized to maintenance tocolysis treatment with either vaginal progesterone or control (either placebo or no treatment). All published randomized studies on progesterone tocolysis were carefully reviewed. Exclusion criteria included maintenance tocolysis in women with preterm premature rupture of membrane, maintenance tocolysis with 17-alpha-hydroxyprogesterone caproate, and maintenance tocolysis with oral progesterone. The summary measures were reported as relative risks (RRs) with 95% confidence interval (CI). The primary outcome was preterm birth (PTB) <37 weeks. RESULTS: Five randomized trials, including 441 singleton gestations, were analyzed. Women who received vaginal progesterone maintenance tocolysis for arrested PTL had a significantly lower rate of PTB <37 weeks (42% vs 58%; RR, 0.71; 95% CI, 0.57-0.90; 3 trials, 298 women). Women who received vaginal progesterone had significantly longer latency (mean difference 13.80 days; 95% CI, 3.97-23.63; 4 trials, 368 women), later gestational age at delivery (mean difference 1.29 weeks; 95% CI, 0.43-2.15; 4 trials, 368 women), lower rate of recurrent PTL (24% vs 46%; RR, 0.51; 95% CI, 0.31-0.84; 2 trials, 122 women), and lower rate of neonatal sepsis (2% vs 7%; RR, 0.34; 95% CI, 0.12-0.98; 4 trials, 368 women). CONCLUSION: Maintenance tocolysis with vaginal progesterone is associated with prevention of PTB, significant prolongation of pregnancy, and lower neonatal sepsis. However, given the frequent lack of blinding and the generally poor quality of the trials, we do not currently suggest a change in clinical care of women with arrested PTL. We suggest instead well-designed placebo-controlled randomized trials to confirm the findings of our metaanalysis.

17-alpha-hydroxyprogesterone caproate for maintenance tocolysis: a systematic review and metaanalysis of randomized trials.

We sought to evaluate the efficacy of maintenance tocolysis with 17-alpha-hydroxyprogesterone caproate (17P) compared to control (either placebo or no treatment) in singleton gestations with arrested preterm labor (PTL), in a metaanalysis of randomized trials. Electronic databases (MEDLINE, OVID, Scopus, ClinicalTrials.gov, and the Cochrane Central Register of Controlled Trials) were searched from 1966 through July 2014. Key words included "progesterone," "tocolysis," "preterm labor," and "17-alpha-hydroxyprogesterone caproate." We performed a metaanalysis of randomized trials of singleton gestations with arrested PTL and treated with maintenance tocolysis with either 17P or control. Primary outcome was preterm birth (PTB) <37 weeks. This metaanalysis was performed following the Preferred Reporting Items for Systematic Reviews and Metaanalyses (PRISMA) statement. The protocol was registered with PROSPERO (registration no: CRD42014013473). Five randomized trials met inclusion criteria, including 426 women. Women with a singleton gestation who received 17P maintenance tocolysis for arrested PTL had a similar rate of PTB <37 weeks (42% vs 51%; relative risk [RR], 0.78; 95% confidence intervals [CI], 0.50-1.22) and PTB <34 weeks (25% vs 34%; RR, 0.60; 95% CI, 0.28-1.12) compared to controls. Women who received 17P had significantly later gestational age at delivery (mean difference, 2.28 weeks; 95% CI, 1.46-13.51), longer latency (mean difference, 8.36 days; 95% CI, 3.20-13.51), and higher birthweight (mean difference, 224.30 g; 95% CI, 70.81-377.74) as compared to controls. Other secondary outcomes including incidences of recurrent PTL, neonatal death, admission to neonatal intensive care unit, neonatal respiratory distress syndrome, bronchopulmonary dysplasia, intraventricular hemorrhage, necrotizing enterocolitis, and neonatal sepsis were similar in both groups. Maintenance tocolysis with 17P after arrested PTL is not associated with prevention of PTB compared to placebo or no treatment in a metaanalysis of the available randomized trials. As 17P for maintenance tocolysis is associated with a significant prolongation of pregnancy, and significantly higher birthweight, further research is suggested.

Predicting fetal lung maturity using the fetal pulmonary artery Doppler wave acceleration/ejection time ratio.

OBJECTIVE: To determine whether the acceleration/ejection time ratio of the fetal main pulmonary artery Doppler waveform (PATET) can accurately predict the results of fetal lung maturity testing in amniotic fluid. METHODS: We prospectively studied pregnant women attending our ultrasound unit for clinically indicated fetal lung maturity testing. An ultrasound examination that included measurement of the PATET was performed before the results of the amniocentesis were reported. The results of the PATET and the surfactant/albumin ratio were compared, and a receiver operating characteristic curve was used to determine the PATET cutoff with the optimal sensitivity and specificity for predicting surfactant/albumin ratio results. p < 0.05 was considered statistically significant. RESULTS: Forty-three patients were included in this study. The receiver operating characteristic curve demonstrated that a PATET cutoff of 0.3149 provided a specificity of 93% (95% CI 77-98%), a sensitivity of 73% (95% CI 48-89%), a negative predictive value of 87% (95% CI 70-95%), and a positive predictive value of 85% (95% CI 58-96%) for predicting immature surfactant/albumin ratio results. CONCLUSION: The PATET may provide a noninvasive means of determining fetal lung maturity with acceptable levels of sensitivity, specificity, and predictive values.

Cervical cerclage.

Cervical cerclage is an obstetric procedure performed for prevention of prematurity. Cerclage was first introduced by Drs Shirodkar and McDonald in the mid-1950s for women with repeated second trimester losses and cervical changes in current pregnancy. Currently, cerclage placement is based on 3 common indications in singleton gestations, including history-indicated (prior multiple early preterm births or second trimester losses), ultrasound-indicated (cervical length <25 mm before 24-wk gestational age in women with prior spontaneous preterm birth) and physical examination-indicated (cervical dilation on manual or physical examination before 24 wk).