Highlights of the Society of Maternal-Fetal Medicine 26th Annual Clinical Meeting, 2006

Editor's Note:
It has come to the attention of SMFM that the published abstract and the oral presentation of the abstract titled "Low molecular weight heparin vs. no treatment in pregnant women with previous preeclampsia or fetal growth restriction who are heterozygote for Factor V Leiden or prothrombin gene G20210A mutation," which was presented at the SMFM 2006 Annual Meeting, by Elena (University of Florence, Florence, Italy) and colleagues^[13] misrepresented the study design. The investigators now disclose that the patients were not randomized. In the words of the investigators, "the subjects treated were those already known to our team, and who had consulted us for pre-conceptional counselling. The choice to offer them treatment with heparin was therefore our therapeutic decision which was explained to these subjects in detail and for which consent was given verbally to us... The control group was made up of those women who had followed the same preconceptional screening in our Institution, but who were not in a direct care relationship with members of our team." The manuscript has been pulled from consideration for publication.

Fetal Pulse Oximetry

The opening plenary session kicked off with a presentation by Bloom (University of Texas Southwestern Medical Center, Dallas, Texas) and colleagues^[1] describing the results of a randomized trial run by the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units (NICHD MFMU) Network concerning fetal pulse oximetry. Intrapartum fetal oxygen saturation monitoring has been offered in recent years as a tool to improve the accuracy of fetal heart rate monitoring for detecting fetuses at risk for hypoxic injury. In this study, more than 5300 nulliparous women at 14 sites around the country in early labor at term had fetal pulse oximeters applied. The subjects were then randomized to either having their fetal oxygen saturation values revealed to their managing clinicians or hidden from them. (In both groups, the fetal oxygen saturation values were recorded.) All patients had fetal scalp electrodes applied for fetal heart rate monitoring. The hope was that knowing the fetal oxygen saturation values would help providers to better interpret fetal heart rate monitor tracings and avoid unnecessary cesarean deliveries for nonreassuring fetal status. Therefore, the primary outcome variable was rate of cesarean deliveries. Patients were stratified at the time of randomization into groups with reassuring and nonreassuring fetal heart rate tracings.

Unfortunately, there was no difference in cesarean delivery rate in the 2 groups enrolled in this study. One of the largest prior studies of fetal pulse oximetry had demonstrated a similar result but did note a reduction in the number of cesareans performed for nonreassuring fetal status in the group of patients whose providers used the fetal oxygen saturation values in their management; that study also found this same group had a higher incidence of cesarean deliveries for labor dystocias.^[2] The current study, however, found no difference in the rates of cesarean deliveries for nonreassuring fetal status or dystocia. More importantly, this study also found no difference in the rates of neonatal morbidity or mortality. Thus, the authors concluded that there was no evidence to support adopting this technology into common practice as a way to improve intrapartum care. Still to be done by the authors was a subgroup analysis of women who had nonreassuring fetal heart rate tracings at the time of randomization.

Notably, another presentation at the meeting by Haydon (Univerisity of California at Irvine, Orange, California) and colleagues^[3] examined whether the administration of oxygen to a laboring woman had an impact on fetal oxygen saturation. It is a little counterintuitive that providing additional oxygen to a healthy woman who already has nearly 100% oxygen saturation of her blood when breathing room air would allow her to deliver any additional oxygen to her fetus. Nevertheless, this study of 24 laboring women with nonreassuring fetal heart rate tracings found that there was a significant increase in the fetal oxygen saturation compared with baseline. This was particularly so for those fetuses with a lower baseline oxygen saturation. For fetuses with a baseline saturation less than 40%, there was a 7% increase in their average oxygen saturation after the mother was given 40% FiO₂ (P = .003) and a 12% rise after the mother was given 100% inspired FiO₂ (P = .001). Whether this increase in fetal oxygen saturation is clinically significant was not explored in this study. Also what is not clear is whether other interventions, such as maternal position change, might have contributed to this improvement in fetal oxygen saturation.

Medscape Ob/Gyn. 2006;11(1) © 2006  Medscape

Cite this: Highlights of the Society of Maternal-Fetal Medicine 26th Annual Clinical Meeting, 2006 - Medscape - Feb 16, 2006.