Fetal scalp stimulation is the practice of pinching or rubbing the fetal head through the dilated cervical os. Some also include deliberately moving the fetal head at abdominal examination as a form of fetal stimulation. It has been theorised that such efforts at stimulation can help to differentiate between a well oxygenated fetus and one that is not. According to the theory, any fetus who responds to such stimulation with an acceleration, or a return to normal variability in the heart rate pattern must be well oxygenated. Fetal scalp stimulation has been used as an adjunct to CTG monitoring, to help guide decisions about whether surgical birth is warranted when the CTG is abnormal.
New research from India set out to see whether this theory holds up (Tahmina, Daniel, & Krishnan, 2022). Women with a singleton pregnancy of 37 weeks or more, and a cephalic presenting fetus were randomised. When the CTG was abnormal those in the treatment group were managed by fetal stimulation (abdominal approach if the cervix was less than 3 cm dilate, and a vaginal approach when the cervix 3 or more cm dilated). No attempts at fetal stimulation were used for those in the control group. CTG monitoring was used intermittently (every 2 hours, no details on the duration of monitoring) in both groups. The decision to proceed to caesarean section was at the discretion of the clinician who was aware of which group the woman was assigned to. Other measures such as position changes, intravenous fluids, and oxygen administration were used in both groups*. Cord blood gases were collected at birth for all babies. The number of women needed to ensure the research was adequately powerful was calculated in advance and this number was met in the study.
Data from 164 women in the fetal stimulation treatment group and 163 in the control group were analysed. The use of caesarean section was not statistically different between the two groups, with both being fairly high at 25.6% in the stimulation group and 30.7% in the control group. There were also no differences in cord artery pH, Apgar scores at 1 or 5 minutes, nursery admission rates or length of stay.
While it is true that fetal stimulation was able to induce a change in the fetal heart rate (97% of fetuses responded with a change in their heart rate), this did not lead to improvements in outcome for the mother or the baby. Fetal stimulation therefore joins my list of things that are used as an adjunct to CTG monitoring that either have been shown not to be effective or lack evidence.
Tahmina, S., Daniel, M., & Krishnan, L. (2022). Manual fetal stimulation during intrapartum fetal surveillance: a randomized controlled trial. American Journal of Obstetrics and Gynecology MFM, 4(2), 100574. https://doi.org/10.1016/j.ajogmf.2022.10057
*There is evidence that giving IV fluids or oxygen are at best pointless and at worst may be harmful in the absence of either hypovolaemia or hypoxia. I must write posts about these one day…