Practice Issues
What is New in the Management of Acute Preterm Labor? Best Articles From the Past Year Fergal D. Malone,
MD
T
his month we focus on current research in the management of acute preterm labor. Dr. Malone discusses four recent publications, which are concluded with a “bottom line” that is the take-home message. The complete reference for each can be found in Box 1 on this page, along with direct links to the abstracts. (Obstet Gynecol 2016;127:398–9) DOI: 10.1097/AOG.0000000000001284
Tests to Predict Imminent Delivery in Threatened Preterm Labour One of the biggest challenges in the management of the pregnant woman who presents with threatened preterm labor is differentiating between the 75% of patients who will not actually deliver early and the remaining minority who will deliver at a significantly preterm gestational age. This article provides an updated review of the large amount of data on tests to accurately identify those patients who will deliver preterm. Qualitative fetal fibronectin (ie, yielding a positive or a negative result) is useful only in terms of its negative predictive value, such that patients with threatened preterm labor with a negative fetal fibronectin result have an 82–99% Dr. Malone is from the Department of Obstetrics and Gynaecology at the Royal College of Surgeons in Ireland, Dublin, Ireland; e-mail: fmalone@rcsi.ie. Financial Disclosure The author did not report any potential conflicts of interest. © 2016 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0029-7844/16
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Box 1. Abstracts Discussed in This Commentary 1. Hezelgrave NL, Shennan AH, David AL. Tests to predict imminent delivery in threatened preterm labour. BMJ 2015;350:h2183. Available at: http:// dx.doi.org/10.1136/bmj.h2183. 2. American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine, Ecker JL, Kaimal A, Mercer BM, Blackwell SC, deRegnier RA, et al. #3: Periviable birth. Am J Obstet Gynecol 2015;213:604–14. Available at: http://dx. doi.org/10.1016/j.ajog.2015.08.035. 3. Manuck TA, Herrera CA, Korgenski EK, Jackson M, Stoddard GJ, Porter TF, et al. Tocolysis for women with early spontaneous preterm labor and advanced cervical dilation. Obstet Gynecol 2015;126:954– 61. Available at: http://dx.doi.org/10.1097/AOG. 0000000000001095. 4. Baker E, Hunter T, Okun N, Farine D. Current practices in the prediction and prevention of preterm birth in patients with higher-order multiple gestations. Am J Obstet Gynecol 2015;212:671.e1–7. Available at: http://dx.doi.org/10.1016/j.ajog.2014.12.031.
chance of remaining undelivered within the subsequent 2 weeks. A positive fetal fibronectin result has very limited utility, with only a 10–40% chance of delivery within the subsequent 2 weeks. A newer quantitative bedside assay of fetal fibronectin appears to perform slightly better, with a 37% probability of preterm birth within the subsequent 2 weeks, when the assay reveals a high concentration (greater than 200 ng/mL). Phosphorylated insulin-like growth factor binding protein-1 is an alternative qualitative cervical swab test, similar to fetal fibronectin, with a similarly high negative predictive value but at a cheaper cost than fetal fibronectin. Another new bedside assay, placental alpha macroglobulin-1, has the advantage of not requiring a speculum examination, such that a simple vaginal swab appears to also have a high negative predictive value. Finally, the article also
OBSTETRICS & GYNECOLOGY
Copyright ª by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
summarizes the performance of transvaginal ultrasound assessment of cervical length in patients with symptomatic preterm labor and describes a 47% positive predictive value for preterm birth within 1 week when the cervix is less than 15 mm when measured before 32 weeks of gestation. As with cervico-vaginal assays, the negative predictive value is 95–97%. The authors suggest that a combination of a negative cervico-vaginal assay result and a cervical length greater than 25 mm suggests such a low chance of delivery within 1 week (less than 5%) that such patients likely do not require admission and treatment.
Bottom Line: Although cervico-vaginal assays have been heavily marketed on the basis of their high negative predictive values, their poor positive predictive values greatly limit their clinical utility. The main role of such tests in patients presenting with acute preterm labor is in the setting of community hospitals to aid in decision making regarding potential transfer to a tertiary care–level medical center. Periviable Birth This consensus statement developed jointly by the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine primarily addresses the problem of periviable birth between 20 and 26 weeks of gestation. It recommends the use of short-term tocolytic therapy (with nifedipine or indomethacin) to allow sufficient time to administer antenatal steroids, as well as magnesium sulfate for neuroprotection, administration of antibiotics to prolong latency after preterm premature rupture of membranes (PROM), and intrapartum antibiotics for group B streptococci prophylaxis when preterm birth is likely after 24 0/7 weeks of gestation, with a grade 1B recommendation. It also suggests that these interventions should be considered when birth is likely between 23 0/7 and 23 6/7 weeks of gestation. Finally, the consensus statement describes limited data suggesting a possible role for emergency cerclage placement at less than 24 weeks of gestation to prolong pregnancy when the fetal membranes are visible at the external cervical os in the absence of uterine contractions or preterm PROM.
Bottom Line: When faced with a patient with preterm labor at gestational ages between 23 and 26 weeks of gestation, it is reasonable to consider using similar obstetric interventions that are commonplace at later gestational ages, such as short-term tocolytics, antenatal steroids, and magnesium for fetal neuroprotection. Antibiotics to prolong latency in the setting of preterm
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PROM can also be considered as early as 20 weeks of gestation. Tocolysis for Women With Early Spontaneous Preterm Labor and Advanced Cervical Dilation This retrospective study from a single health care system in Utah reviewed the experience with tocolytics given to 233 patients with singleton pregnancies with preterm labor and cervical dilation between 4 and 8 cm, compared with 64 similar patients who did not receive tocolytics. Indomethacin was the most common tocolytic used, although some patients received magnesium sulfate or nifedipine or a combination of multiple tocolytics. In the group who received tocolytics, significantly more remained pregnant after 48 hours compared with those who did not receive tocolytics (24% compared with 8%), but there was no difference in those remaining undelivered after 7 days (5% in both). Although not powered to reveal differences in neonatal outcomes, no differences in initial neonatal outcomes were noted. The strength of this study is the fact that patients were all experiencing true preterm labor, rather than just preterm contractions. However, the study was limited by its retrospective, nonrandomized design.
Bottom Line: Tocolytics should be considered in the setting of preterm labor, even with very advanced cervical dilation, if for no other reason than to increase the rate of successful steroid administration and potential transfer to a tertiary care medical center. Current Practices in the Prediction and Prevention of Preterm Birth in Patients With Higher-Order Multiple Gestations This questionnaire of Canadian maternal-fetal medicine specialists gives a snapshot of contemporary practice in terms of management of preterm labor in higher-order multiple gestations (triplets or higher). The vast majority (81%) would use tocolytic agents for threatened preterm labor, with calcium channel blockers being by far the most popular (94%), followed by nonsteroidal anti-inflammatory drugs (5%) and nitroglycerin transdermal patch (24%).
Bottom Line: Given the difficulty in performing randomized trials of preterm labor in special populations, such as higher-order multiple gestations, surveys of contemporary attitudes to treatment choices are valuable for informing clinical practice. Despite special risks associated with their use in higher-order multiple gestations, tocolytic use for threatened preterm labor is almost universally practiced by maternal-fetal medicine specialists in contemporary practice.
Malone
What’s New in Acute Pretern Labor?
Copyright ª by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
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