How routine should screening for preterm birth be in at-risk nulliparas?

February 5, 2016

Article

Dispatches from the SMFM 36th Pregnancy meeting looks at how routine screening for preterm birth should be in at risk pregnancies; a look at the role of cervical smooth muscle cells in preterm birth; the potential association between preterm birth and maternal mortality. Plus: A look at the impact of recommendations on cesarean delivery.

A study by an investigator from the Eunice Kennedy Shriver National Institute of Child Health and Human Development NuMoM2b Network casts doubt on routine use of self-collected fetal fibronectin (fFN) and serial transvaginal cervical length (TVCL) measurements in nulliparous women at risk of subsequent spontaneous preterm birth (sPTB). The results were presented during an oral plenary session at the Society for Maternal-Fetal Medicine’s 36^th Annual Pregnancy Meeting.

The research was conducted at 8 clinical sites and designed to determine whether universal screening with TVCL and fFN can be used to accurately predict sPTB in nulliparous women. Quantitative fFN was performed on the participants a 3 time points (V1 6-14 weeks; V2 16-22 weeks; V3 22-30 weeks) and TVCL was performed at V2 and V3. Quantitative fFN was run on self-collected swabs and TVCL was measured by certified sonographers. Clinicians were notified if TVCL was <15 mm (n=301) but fFN results were not reported. The investigator used previously described thresholds to evaluate the results and also looked at changes in fFN and TVCL between visits.

Of the 9,352 women with at least one TVCL or fFN measurement and necessary pregnancy outcome data, 460 (4.9%) had sPTV. Of the 301 women with TVCL <15 mm, only 59 received progesterone. Of the women with sPTB, TVCL at V2 identified 34/428 (7.9%) and V3 identified 94/398 (23.6%) using the 25-mm threshold. “The addition of quantitative fFN to TVCL measurement did not increase the predictive ability of TVCL alone,” the author concluded. “The routine use of self-collected quantitative fFN and TVCL to screen for risk of sPTB is not justified in a nulliparous population,” he said.

Esplin M. The use of serial cervical length and quantitative fetal fibronectin to identify nulliparous women at risk of subsequent spontaneous preterm birth. Am J Obstet Gynecol. 2016;214(1);S24

NEXT: Stretch in cervical smooth muscle cells and preterm birth

Stretch in cervical smooth muscle cells and preterm birth

A small study presented at the Society for Maternal-Fetal Medicine’s 36^th Annual Pregnancy Meeting may point the way to a potential mechanism underlying preterm birth (PTB). The results, reported in a poster, were published in The American Journal of Obstetrics & Gynecology.

The aim of the research, by investigators from Columbia University, was to define the role of cervical smooth muscle cells (CSMC) in normal and premature cervical remodeling (PCR). The study was designed to determine whether CSMC secrete matrix metalloproteinases (MMPs)-collagen remodeling enzymes-and whether CSMC stretching induces and triggers increased secretion of those enzymes, particularly in women with a history of PCR.

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CSMC were isolated from 4 women with 14- to 16-week pregnancies who were scheduled for cerclage and who had a history of PTB <28 weeks, and from 4 gestational age-matched controls who were undergoing pregnancy termination. Smooth muscle cells were identified using immunocytochemistry for alpha-SMA, SM22 and desmin. A Flexcell system then was used to apply cyclical stretch and then concentrations of MMP1, 2, 7, 9 and 10 in the basal media were determined by Luminex. Statistical analyses included logistic regression, generalized estimated equation, ANOVA, and Student’s t-test.

The researchers found that before and after 24 hours of cyclical stretch, smooth muscle cell markers were evident. In the women with a history of PCR compared with the controls, cyclical stretch resulted in significantly increased secretion of MMP2 (P=0.003). “This abnormal CSMC stretch response, characterized by increased MMP2 secretion,” the authors concluded, “may elucidate a potential mechanism in the pathophysiology of PCR and PTB.

Vink J, Qin S, Praditpan P, et al. 201: Human cervical smooth muscle stretch increases matrix metalloproteinase secretion: a new mechanism to explain premature cervical remodeling. Am J Obstet Gynecol. 2016;214(1);S122

NEXT: Severe maternal morbidity and preterm birth

Severe maternal morbidity and preterm birth

A retrospective cohort study led by investigators from Cedars-Sinai Medical Center shows an association between severe maternal morbidity and preterm birth (PTB). The findings were presented during an oral concurrent session at the Society for Maternal-Fetal Medicine’s 36^th Annual Pregnancy Meeting.

Published in The American Journal of Obstetrics & Gynecology, the results are from an analysis of deliveries in 16 hospitals in California from July 2012 to June 2013. ICD-9 codes were used to identify severe illness, prolonged postpartum length of stay, intensive care unit admission, and transfusion among the mothers. The objective was to determine risk factors associated with women who had true-positive severe maternal morbidity (SMM).

Of the 66,646 women represented, 491 (0.7%) had true SMM. Compared with the women who screened negative, they were significantly more likely to be older than age 35 (33% vs. 24%; P<.0001), African-American (12% vs 7%; P<.0001), and to have a multiple gestation (9% vs 2%; P<.0001) and a prior cesarean delivery (31% vs 17%; P<.0001). In the women with SMM, PTB also was significantly more common, including delivery at <32 weeks (17.8% vs 1.4%; P<.0001). Looking at the diseases that underlay the SMM, the authors found that obstetric hemorrhage was the most common (42%), followed by hypertensive disorders (20%) and placental hemorrhage (14%). Cardiovascular disease was the underlying problem in only 3% of women with SMM.

The history of cesarean delivery in one-third of the women who experienced obstetric hemorrhage, the researchers said, supports ongoing national efforts to reduce primary cesarean delivery. The high prevalence of PTB in women with SMM, they also noted “underscores the importance of appropriate level care availability for both mothers and their newborns.”

Commenting about the practical implications of the research, Sarah J. Kilpatrick, MD, PhD, the principal investigator on the study, told Contemporary OB/GYN, “This study highlights the importance of actually reviewing the charts of women who have screened positive for severe maternal mobility because most
of those women will not meet criteria of being severely ill. Further, placental hemorrhage and hypertension accounted for nearly 75% of the women who delivered at less than 32 weeks, supporting the need for appropriate levels of care for both mother and baby in taking care of women with severe morbidity.”

Kilpatrick S, Abreo A, Lanner-Cusin K, Main E. Severe maternal morbidity is associated with high rate of preterm delivery. Am J Obstet Gynecol. 2016;214(1);S28

NEXT: Impact of joint recommendations on cesarean delivery

Impact of joint NICHD, SMFM, and ACOG recommendations on cesarean delivery

Investigators from France say that implementing recommendations issued jointly by major medical organizations in the United States for preventing first cesarean deliveries reduced their hospital’s cesarean rate after induction of labor (IoL) and for arrest of labor (AoL). The results were presented in 2 posters during the Society for Maternal-Fetal Medicine’s (SMFM) 36^th Annual Pregnancy Meeting.

The institution that achieved the results was Poissy Saint-Germain Hospital in Poissy, France. The researchers performed the before-and-after studies to evaluate changes in cesarean delivery rates after IoL and for AoL. They looked at trends in these outcomes before and after implementation of the recommendations from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, SMFM, and the American College of Obstetricians and Gynecologists.

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Before March 2014, once cervical dilation reached 4 cm, the hospital defined failed induction (FI) as a failure to generate cervical change despite regular contractions after 8 hours of oxytocin administration with artificial membrane rupture. Second-stage arrest was defined as no progress for 3 hours or more of adequate contractions. First-stage AoL was diagnosed by cervical dilatation of 4 cm, ruptured membranes, and 3 hours of adequate contractions or 4 hours of inadequate contractions with no cervical change. Second-stage AoL was no progress, regardless of parity. After March 2014, the recommendations from the US organizations were adopted.

For the studies, the authors compared maternal and neonatal outcomes from March 2013 to February 2014 (before) and from June 2014 to May 2015 (after). The population for the IoL analysis was 679 and 591 women, respectively, with low-risk singleton pregnancies at term in vertex presentations. The population for the AoL analysis was 2607 and 2480 women, respectively, with low-risk singleton pregnancies at term in vertex presentation and spontaneous labor with an epidural during the before and after periods.

Implementation of the recommendations, the authors reported, reduced the cesarean delivery rate in IoL without increasing maternal or neonatal morbidity. In the “before” period, the overall cesarean delivery rate was 19.6%, the cesarean rate for non-reassuring fetal heart rate (FHR) was 12.5%, and the cesarean rate for FI was 7.1%, compared with 14.1%, 8.7%, and 5.4%, respectively, in the “after period.” Rates of cesarean for AoL fell from 6.6% overall to 5% and rates of cesarean for non-reassuring (FHR) fell from 3.8% to 1.9%. Instrumental vaginal delivery rates did not change, nor did maternal or neonatal morbidity differ significantly between the two periods of time.

Rozenberg P, Thuillier C, Quibel T, et al. Changes in the cesarean rate after induction of labor after implementation of the recommendations for practice of the Joint Eunice Kennedy Shriver NICHE, the SMFM, and the ACOG workshop to prevent the first cesarean. Am J Obstet Gynecol. 2016;214(1);S362

Rozenberg P, Thuillier C, Quibel T, et al. Changes in the cesarean rate for arrest of labor after implementation of the recommendations for practice of the Joint Eunice Kennedy Shriver NICHD, the SMFM, and the ACOG workshop to prevent the first cesarean. Am J Obstet Gynecol. 2016;214(1);S268