Sinusoidal pattern is indicated by an undulating waveform evenly distributed between 120 and 130 bpm baseline. There is minimal variability. A FHR baseline pattern consisting of a series of cycles that are extremely smooth & regular in amplitude & duration Resembles a perfect letter “S” on its side May be benign Causes: o Fetal anemia o Chronic fetal bleeding o Fetal isoimmunization o Twin-to-twin transfusion o Umbilical cord occlusion o CNS malformations Accelerations: Visually apparent abrupt increase from FHR baseline Term infants: o Onset to peak < 30 seconds; acme ≥ 15 bpm o Duration ≥ 15 seconds < 2 minutes Preterm: o Onset to peak < 30 seconds; acme ≥ 10 bpm o Duration ≥ 10 seconds
Prolonged acceleration duration ≥ 2 minutes < 10 minutes Decelerations: Abrupt: onset to nadir < 30 seconds Gradual: onset to nadir > 30 seconds Basic Tx: o Call for help! o Turn off Pitocin o Position change (lateral or knee-chest) o IV fluid initiation/increase o Oxygen o Notify MD/CNM o Vaginal Exam unless contraindicated (i.e. preterm, placenta previa) with fetal scalp stimulation Early Decels: Visually apparent gradual decrease & return to FHR baseline associated with UC Onset to nadir ≥ 30 seconds Nadir occurs at peak of contractions Cause: HEAD COMPRESSION Late Decels: Visually apparent gradual decrease & return to baseline FHR associated with contractions Onset to nadir ≥ 30 seconds Onset, nadir, and recovery occur after onset, peak and recovery of contraction Caused by UTEROPLACENTAL INSUFFICIENCY; thus, they are always ominous. To optimize uteroplacental blood flow and fetal oxygenation, the pt. should be place in the left lateral position Variable Decels : Visually apparent abrupt decrease from FHR baseline; may occur with or without contractions Onset to beginning of nadir < 30 seconds Decrease ≥ 15 bpm Duration ≥ 15 seconds & < 2 minutes from onset to return to baseline FHR Inherently vary in timing, shape and duration During variable decels, FHR drops below 90 bpm very quickly as fetal blood flow through the umbilical cord is interrupted. FHR returns rapidly to baseline as soon as the cord compression is relieved. Variable decelerations are caused by CORD COMPRESSION. Tx focuses on relieving cord compression. If these interventions fail, C-section must be done. To decrease cord compression, infuse saline into the uterus via an intrauterine pressure catheter and/or reposition the pt. to a position that improves fetal heart rate (not supine). Prolonged decels: Visually apparent decrease in FHR below baseline
Decrease ≥ 15 bpm Duration ≥ 2 minutes & < 10 minutes from onset to return to baseline Fetal heart rate: Normal FHR baseline is 120-160 bpm.
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