Predictive value of quantitative fetal fibronectin for spontaneous preterm birth in asymptomatic pregnancies: a systematic literature review and meta-analysis

OBJECTIVE

Tests capable of accurate prediction of spontaneous preterm birth (sPTB) are crucial to inform clinical decisions to prevent neonatal deaths and reduce the risk of morbidity in surviving infants. A systematic literature review and meta-analysis were performed to assess the utility of the quantitative fetal fibronectin (fFN) test to predict sPTB at different test concentration thresholds.

METHODS

Literature searches were conducted in MEDLINE, Embase, and the Cochrane Library in May 2022. Observational studies and clinical trials investigating the clinical utility of the quantitative fFN test in asymptomatic pregnancies prior to 37 weeks of gestation were eligible for inclusion. Meta-analysis quantified the risk of sPTB prior to four gestational age milestones (<28, <30, <34 and <37 weeks) based on quantitative fFN levels. No risk of bias assessment was performed however, clinical and methodological heterogeneity was explored to determine the feasibility of performing analyses.

RESULTS

11 studies showed a quantitative assessment of fFN can differentiate between very high and very low risks of sPTB in asymptomatic pregnancies with <10% of women with very low fFN (<10 ng/mL) versus 37-67% of women with very high fFN (>200 ng/mL) delivering before 34 weeks. A meta-analysis of two studies showed, albeit with a low number of events, the odds of sPTB prior to 28 weeks was nine times higher in women testing positive at ≥50 ng/mL, whereas the odds of sPTB was 25 times higher in women with fFN concentrations >200 ng/mL (versus <50 ng/mL reference). Similarly, pooling three studies showed the odds of sPTB prior to 37 weeks was four times higher in women who tested positive at ≥50 ng/ml whereas the odds of delivery before 37 weeks was seven times higher for women with fFN concentrations ≥200 ng/ml (versus <50 ng/mL reference).

CONCLUSION

Quantitative fFN testing demonstrates increased predictive capabilities and utility of fFN testing in clinical practice, potentially preventing unnecessary intervention for women at very low risk and allowing an opportunity to optimize the management of asymptomatic patients at high risk of preterm delivery.

Availability and use of fetal fibronectin testing and transvaginal ultrasound for preterm labor evaluation in the United States

OBJECTIVE

Measure availability and use of fetal fibronectin (fFN) testing and transvaginal ultrasound to measure cervical length (TVCL) for symptomatic preterm labor (PTL) patients. Additionally, assess the presence and impact of PTL triage protocols.

STUDY DESIGN

Cross-sectional online survey among clinicians from 255 unique hospitals regarding prior 12-month practices (pre-COVID-19).

RESULTS

fFN testing was always available in 87% (221) of hospitals, while TVCL was always available in 69% (175) of hospitals. Utilization was lower: fFN specimens were often/always collected in 61% (156) of hospitals and TVCL was often/always performed in 43% (110) of hospitals. fFN testing was significantly more likely than TVCL to be available and used (p < .05). Written PTL protocols were available in 47% (121) of hospitals but not consistently followed.

CONCLUSION

The most accurate risk assessment approach for imminent spontaneous preterm birth is the implementation of a universal screening program for symptomatic patients, including fFN testing and TVCL.

Prior authorization and its impact on access to obstetric ultrasound

Prior authorization is a process requiring health care providers to obtain advance approval from a payer before a patient undergoes a procedure for the study to be covered. Prior authorization was introduced to decrease overutilization of ultrasound procedures. However, it has led to unanticipated consequences such as impeding access to obstetric imaging, increased administrative overhead without reimbursement, and contribution to physician frustration and burnout. Payers often use intermediary radiology benefit management companies without providing specialty-specific review in a timely manner as is requisite when practicing high-risk obstetrics. This article proposes a number of potential solutions to this problem: (1) consider alternative means to monitor overutilization; (2) create and evaluate data regarding providers in the highest utilization; (3) continue to support and grow the educational efforts of speciality societies to publish clinical guidelines; and (4) emphasize the importance of practicing evidence-based medicine. Understanding that not all health plans may be willing or able to collaborate with health care providers, we encourage physicians to advocate for policies and legislation to limit the implementation of prior authorization within their own states.

Current perspectives on the use of fetal fibronectin testing in preterm labor diagnosis and management

One in 10 infants in the United States is delivered preterm (ie, before the 37th week of pregnancy), contributing to the significant burden on the national healthcare system. Nevertheless, a lack of agreement continues among obstetric professional societies on guidelines for standardization of the approach to the diagnosis and management of patients with symptoms of preterm labor (PTL). This disparity in consensus has likely resulted in poor identification of women at an increased risk for preterm birth (PTB). This paper presents an overview of several clinical guidelines and recommendations from a variety of studies regarding the use of fetal fibronectin (fFN) testing and transvaginal ultrasound (TVU) cervical length measurement, 2 tools that are used to assess the risk of spontaneous PTB (sPTB) in women with symptoms of PTL. We identify areas of commonality and discord within these publications. Although inconsistencies exist among the published guidelines, algorithms, and studies on how to diagnose and treat women with symptoms of PTL, each of them supports the use of fFN in conjunction with TVU for assessing the risk of sPTB. In addition, we review a case study from a regional hospital system with results demonstrating the benefits to patients and process outcomes when PTL assessment protocols are standardized, incorporating both fFN and TVU test results. In the absence of consensus on this topic, healthcare providers, administrators, and payers must navigate conflicting recommendations and identify areas of agreement for this evaluation within their own local settings.

Obstetric Ultrasound Efficiency and Accuracy Using a Protocol-Based Examination

OBJECTIVES

Obstetric ultrasound imaging requires the acquisition of a standard set of maternal and fetal images. Our objective was to evaluate the impact of implementation of a protocol-based ultrasound examination on the duration of ultrasound examinations, examination completion, and accuracy of documentation.

METHODS

We conducted a case-cohort study. Obstetric ultrasound examinations performed in the first, second, and third trimesters were reviewed before and after implementation of a protocol-based ultrasound examination. The duration of the ultrasound examination, number of missing required images, and documentation of missing images were abstracted from an image archival system. To account for clustering by sonographer, 3 mixed effects models with a fixed effect for protocol and a random intercept for sonographer were used to evaluate the effect on the total time of the examination, number of missing images, and whether missing images were documented.

RESULTS

A total of 100 ultrasound examinations were compared: 50 before and 50 after implementation of the protocol. Statistically significant differences between outcomes before and after protocol implementation were observed for all outcomes. After implementation of the protocol, the average duration of ultrasound examinations decreased by 7.62 minutes (95% confidence interval [CI], 3.57-11.68 minutes); the number of missing images was reduced by 5.81 per examination (95% CI, 4.24-7.39); and proper documentation of missing images increased by 40.24% (95% CI, 22.77%-57.71%).

CONCLUSIONS

Implementation of a software protocol-based ultrasound examination significantly improved the efficiency and accuracy of obstetric ultrasound examinations in this study.

Angle correction can be used to measure peak systolic velocity in the fetal middle cerebral artery

OBJECTIVE

The objective of the study was to compare Doppler ultrasound measurements of the fetal middle cerebral artery peak systolic velocity (MCA-PSV) obtained at a 0 degrees angle of insonation to assessment at 30 degrees and 30 degrees with angle correction.

STUDY DESIGN

Patients between 14 and 36 weeks' gestation were enrolled (n = 66). MCA-PSV measurements were assessed at 0 degrees , 30 degrees , and 30 degrees with angle correction. The data were analyzed using a mixed model adjusted for gestational age. Pairwise comparisons of mean MCA-PSV measurements were made using the Tukey multiple comparison test.

RESULTS

All measurements were obtained for 50 fetuses (76%). Mean MCA-PSV measurements were statistically different between 0 degrees vs 30 degrees (P = .03 to < .001) but not between 0 degrees vs 30 degrees with angle correction (P = .34-.99) at each of the 5 gestational age groupings.

CONCLUSION

Assessment of the MCA-PSV at 0 degrees and 30 degrees with angle correction provides comparable measurements during the second and third trimester of pregnancy.

Combined plasmapheresis and intravenous immune globulin for the treatment of severe maternal red cell alloimmunization

OBJECTIVE

The objective of the study was to report the maternal and perinatal outcome in patients with severe red cell alloimmunization in pregnancy who were treated with immunomodulation therapy.

STUDY DESIGN

This was a retrospective multicenter case series. Patients with a history of early second-trimester fetal loss secondary to severe maternal red cell alloimmunization or patients with markedly elevated maternal antired cell titers felt to be consistent with poor fetal outcome were offered treatment. Therapy consisted of serial plasmapheresis followed by weekly infusions of intravenous immune globulin (IVIG). Maternal titers were measured before and after plasmapheresis.

RESULTS

Pregnant patients with either a history of a previous perinatal loss (n = 7) or markedly elevated maternal antibody titers (n = 2) were treated with combined plasmapheresis and IVIG. All 9 fetuses subsequently required intrauterine transfusions (median 4; range 3-8). All infants survived with a mean gestational age at delivery of 34 weeks (range 26-38 weeks). Maternal antired cell titers were significantly reduced after plasmapheresis (P < .01) and remained decreased during IVIG therapy. Serial peak middle cerebral artery velocities remained below the threshold for moderate to severe fetal anemia during therapy.

CONCLUSION

Combined immunomodulation with plasmapheresis and IVIG represents a successful approach to the treatment of severe maternal red cell alloimmunization.