Caroline Helwick

February 06, 2015

SAN DIEGO — ST segment analysis (STAN) used as an adjunct to conventional intrapartum monitoring of the fetal heart rate does not improve perinatal outcomes or reduce operative deliveries, at least in the United States, new research has shown.

In the largest randomized controlled trial of this technology and one of the first to evaluate STAN in this country, "we found no differences in the effect of STAN on the primary outcome or on Cesarean or operative delivery," said George Saade, MD, from the University of Texas Medical Branch in Galveston.

These results are in contrast to the findings of European studies.

Dr. Saade presented the study results here at the Society for Maternal-Fetal Medicine (SMFM) 2015 Annual Pregnancy Meeting.

Fetal electrocardiogram (ECG) analysis of the ST segment, which is similar to adult cardiac stress testing, is used in Europe as an adjunct to conventional intrapartum monitoring of the fetal heart rate and has been approved by the US Food and Drug Administration.

"By the time we proposed our study, a number of studies supported fetal ECG," Dr. Saade reported.

A Cochrane review demonstrated a reduction in a number of neonatal adverse events, including neonatal encephalopathy, metabolic acidosis, operative vaginal delivery, operative delivery, and the need for a fetal blood sample (Cochrane Database Syst Rev. 2006;3:CD000116).

Differences in Patient Characteristics

This and other studies, Dr. Saade explained, "generated enthusiasm, but also concerns," many of them pertaining to the fact that differences between patient characteristics in Europe and the United States could "affect its generalizability" to all populations.

Therefore, "we sought to determine whether STAN would improve perinatal outcomes and decrease operative deliveries at 26 hospitals in the United States," he said.

The study involved women in labor whose physicians were affiliated with one of 26 community and academic hospitals in the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal–Fetal Medicine Units Network.

The women were attempting a singleton vaginal delivery, had a gestational age of at least 36 weeks, and were 2 to 7 cm dilated.

Of the 11,108 women, 5532 were randomized to open monitoring, where STAN information was displayed on the monitor, and 5576 were randomized to masked monitoring, where the information was not displayed.

At baseline, there were no significant differences in characteristics between the groups. All care providers were trained and certified in STAN, and a training pilot study was completed at each site before the trial started.

The primary outcome was a composite of at least one of the following: intrapartum fetal death, neonatal death, Apgar score of 3 or less at 5 minutes, neonatal seizure, cord arterial pH of 7.05 or less plus base deficit of at least 12 mmol/L, intubation for ventilation at delivery, and neonatal encephalopathy.

No Added Benefit With STAN

In the intent-to-treat analysis, the primary outcome was not significantly different between the open and masked groups (1.4% vs 1.3%; relative risk [RR], 1.14; 95% confidence interval, 0.83 - 1.57).

All components of the composite outcome were similar in the two groups. "Fortunately, the rates of adverse neonatal outcomes were low overall," Dr. Saade reported.

There was no significant difference between the two groups in any of the secondary outcomes, which included delivery method, indication for Cesarean delivery, indication for the use of forceps or vacuum, postrandomization labor duration, occurrence of chorioamnionitis, need for blood transfusion, occurrence of postpartum endometritis, length of hospital stay, occurrence of dystocia, Apgar score at 5 minutes, nursery admission, meconium aspiration syndrome, and major congenital malformation.

The findings were consistent in all subgroups when patients were stratified by baseline fetal heart rate, parity, birthing center, timepoint of delivery, race and ethnicity, type of labor, baseline cervical dilation, or whether the hospital had more or less than 500 study participants.

This study had a number of strengths, Dr. Saade reported. This was the largest randomized trial of fetal ECG, valid cord gases were available for 96.5% of subjects, providers had extensive training and certification and the study included a pilot phase, there was real-time review and feedback followed by retraining where necessary, outcomes were centrally reviewed, and there was an independent data coordinating center.

The results of this study are more applicable to practices in the United States than results from studies performed elsewhere, Dr. Saade emphasized.

He described the diversity of the 26 hospitals and said he believes they are typical of practices in the United States. "After 4 years of doing a study on more than 11,000 patients, I believe our results can clearly be called 'generalizable'," he said.

The largest study ever conducted in the United States showed negative results.

This study highlights the need for caution when extrapolating results from studies conducted outside the United States, he explained, and the importance of testing medical interventions and technologies in the settings and populations where they will be applied.

Although the study raises concerns, fetal ECG is "not overused," said Vincenzo Berghella, MD, from Thomas Jefferson University in Philadelphia, who is president of the SMFM and who moderated the plenary session.

In European studies, results with STAN were positive. Unfortunately, the "largest study ever conducted in the United States showed negative results," said Dr. Berghella.

"Before we take on such a screening test, I think we should pause, because STAN does not seem to have the effect that we had hoped for," he told Medscape Medical News.

Dr. Saade and Dr. Berghella have disclosed no relevant financial relationships.

Society for Maternal-Fetal Medicine (SMFM) 2015 Annual Pregnancy Meeting: Abstract 1. Presented February 5, 2015.


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