Normal (Reassuring) Antenatal Cardiotocograph
A 35-year-old G3P2 with diet-controlled gestational diabetes attends at 38 weeks of gestation for planned induction of labor. She has no pain, bleeding or fluid loss. The uterus is soft, non-tender and corresponds to dates, and the cervix is closed and uneffaced. Cardiotocography shows a baseline of 135 beats/min, variability of 12 beats/min, present accelerations and no decelerations. Which of the following best describes this tracing?
- A.Recurrent late decelerations
- B.Recurrent early decelerations
- C.Recurrent variable decelerations
- D.Normal reassuring patternCorrect
Explanation
A reassuring antenatal cardiotocograph has four components: a baseline of 110 to 160 beats/min, moderate variability of 6 to 25 beats/min, present accelerations, and absent decelerations. This tracing meets all four criteria, so it is normal and induction can proceed as planned. Variability is generated by the interplay of sympathetic and parasympathetic input to the fetal heart and is the most reliable indicator of adequate central oxygenation and an intact autonomic nervous system. Accelerations, defined as a rise of at least 15 beats/min lasting at least 15 seconds after 32 weeks, further confirm fetal wellbeing. The clinical context also argues against any deceleration pattern: she is not in labor, has no contractions, and the cervix is closed, so there is no head compression, no cord compression during contractions and no contraction-related reduction in placental perfusion. Late decelerations require contractions and indicate uteroplacental insufficiency; early decelerations require head compression in labor; variable decelerations require cord compression. Gestational diabetes does raise the risk of stillbirth and macrosomia, which is why fetal surveillance and timely delivery are planned, but the tracing itself is normal here.
Why each option
- A.
- Late decelerations occur with contractions and indicate uteroplacental insufficiency; there are no contractions and no decelerations on this tracing.
- B.
- Early decelerations arise from fetal head compression during labor; the cervix is closed and she is not in labor.
- C.
- Variable decelerations reflect cord compression, typically during contractions or with oligohydramnios, neither of which is present.
- D.
- Correct. Normal baseline, moderate variability, present accelerations and absent decelerations define a reassuring tracing.
Reference: ACOG Practice Bulletin No. 145, Antepartum Fetal Surveillance, reaffirmed 2023
This is one of 3,306 questions in the MedBoardSA SMLE bank, with timed test mode, tutor mode, and progress tracking by topic.
Practise the full bank