Cardiotocography (CTG) was introduced in the 1960s to monitor fetal cardiac activity in utero. Its use in the intrapartum period is an attempt to predict fetal acidosis, allowing clinicians to intervene before fetal asphyxia occurs. However, it tends to have poor sensitivity and specificity. When fetal blood sampling (FBS) is used in conjunction with CTG, it results in more accurate determination of fetal acidosis, but even then it does not adequately predict fetal outcome.

ST-analysis of the fetal electrocardiogram (STAN) was introduced in the 2000s. This method analyses fetal ST-segments and T-waves, which are said to change in response to hypoxia before the development of neurological damage. In this article by Becker et al in the September issue of the British Journal of Obstetrics and Gynaecology, they looked at when STAN recommended FBS and whether fetal acidosis was actually present. With continued fine-tuning of STAN criteria, it may redefine intrapartum monitoring.

Summary: http://onlinelibrary.wiley.com/doi/10.1111/j.1471-0528.2011.03027.x/abstract
Full article (requires access to RCSI library):
http://onlinelibrary.wiley.com.proxy.library.rcsi.ie/doi/10.1111/j.1471-0528.2011.03027.x/full
PMID: 21668767