Which of the following defines tachysystole in the context of labour induction with oxytocin?
- A More than 4 contractions in 10 minutes over two consecutive 10-minute windows
- B More than 5 contractions in 10 minutes, averaged over a 30-minute window ✓
- C Any contraction lasting longer than 90 seconds
- D Contractions exceeding 60 mm Hg peak pressure on intrauterine monitoring
Correct answer: B. More than 5 contractions in 10 minutes, averaged over a 30-minute window
Explanation
Tachysystole is defined as more than five contractions in 10 minutes, averaged over a 30-minute window, irrespective of fetal heart rate status. It applies to spontaneous and stimulated labour alike. The definition deliberately uses an averaging window rather than consecutive windows, and it does not require abnormal fetal heart rate or contraction duration to be present.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.