From the Research
CST intervals should be determined based on individual risk factors and pregnancy progression, with weekly testing starting at around 32 weeks gestation for high-risk pregnancies, and more frequent testing for conditions like preeclampsia, intrauterine growth restriction, or diabetes. The frequency of Contraction Stress Test (CST) intervals is crucial for monitoring high-risk pregnancies. According to the most recent and highest quality study available, which is from 2023 1, the interpretation of cardiotocography signals, including those from CST, is subject to high interobserver variability, and the development of reliable computer-aided systems is still ongoing. However, this study does not directly address the frequency of CST intervals. Looking at other studies, the 1995 study 2 mentions that the CST should not be the only form of testing to follow high-risk pregnancies, but its proved efficacy and close correlation with intrapartum monitoring make it an essential tool. The 2008 study 3 provides an overview of antenatal fetal assessment methods, including the CST, but does not specify the optimal testing frequency. The 1975 study 4 used the CST to evaluate fetal reserve prior to labor and found that a negative CST appears to be a reliable guide to the ability of the fetus to tolerate labor if it ensues within 1 week. However, this study does not provide information on the optimal testing frequency. The 1986 study 5 investigated the use of oxytocin nasal spray for the induction of contractions in the CST and found that the application of 8 IU of oxytocin nasal spray is sufficient to induce in about 95% of the cases an oxytocin-challenge-test. However, this study does not address the frequency of CST intervals. In clinical practice, the frequency of CST intervals is typically determined based on individual risk factors and pregnancy progression. For example:
- Weekly testing starting at around 32 weeks gestation for high-risk pregnancies
- Twice-weekly testing for conditions like preeclampsia, intrauterine growth restriction, or diabetes
- Testing every 2-3 days for post-term pregnancies (beyond 41 weeks) It is essential to consult with an obstetrician to determine the appropriate CST interval for a specific situation, as individual risk factors and pregnancy progression will influence the optimal testing schedule.