Can observed fetal breathing predict successful labor induction?

Objective: To determine if a quantified incidence of fetal breathing activity, observed continuously for 1 h, can aid in the prediction of successful induction of labor at term. Methods: We enrolled gravidas scheduled to undergo indicated induction of labor (study group) and non-laboring gravidas of similar gestational age who were allowed subsequently to enter spontaneous labor (control group) for observation of fetal breathing activity before the onset of labor. Each group received 1 h of continuous ultrasound observation of fetal breathing movements, acquired and analyzed off line by a validated software program. Based on a previously published threshold of fetal breathing movement incidence (4%) associated with a spontaneous onset of labor, power analysis (β = 0.20) required a total minimum enrollment of 24 patients. Main outcome variables included length of labor, the interval to entering spontaneous or induced labor, and success of induction, as defined by entry into active phase of labor. Groups were compared with Student's t test and Chi-square test (P < 0.05, considered significant). Results: Thirty study and 18 control patients had ultrasound observations for fetal breathing movement incidence, rate, and breath interval. The mean incidence of breathing was 24% in the study group and 31% in the control group. A 4% fetal breathing movement incidence was used to divide both groups into 'breathers' (81% study, 95% control) and 'non-breathers' (19% study, 5% control). 'Breather' and 'non-breather' subgroups were similar for success of induction, length of labor, and cervical ripening. The induction and control groups were also similar for the other maternal and fetal variables analyzed. Conclusions: Prospective observation of fetal breathing movement incidence does not improve the prediction of the successful outcome of labor induction at term.