Fetal heart rate monitoring in nonobstetric surgery: a systematic review of the evidence

Objective: Concern for fetal well-being during maternal nonobstetric surgery may result in obstetricians and other maternity care providers being asked to perform intraoperative fetal heart rate (FHR) monitoring. We systematically reviewed the evidence regarding the use of FHR monitoring during nonobstetric surgery after potential fetal viability (>22 weeks gestational age), and examined the FHR patterns and outcomes reported.

Data sources: A systematic review of the evidence was performed. Sources included databases (MEDLINE, EMBASE, Cochrane, and CENTRAL), hand searching, guidelines, conference proceedings, and literature reviews. Online searching was performed to include literature published from 1966 to May 2019.

Study eligibility criteria: All studies reviewing care of pregnant women undergoing nonobstetric surgery where FHR monitoring was performed intraoperatively. Data were extracted from appropriate full-text articles using a data abstraction form.

Study appraisal and synthesis: Case reports and case series only were identified. A total of 74 cases were reviewed, encompassing maternal general surgery (n = 41, cardiovascular surgery (n = 13) and neurosurgery/orthopedics (n = 20). Median gestational age at time of maternal surgery was 30 weeks (range, 22-36 weeks). In 41 cases, findings of FHR monitoring were not reported. Abnormal tracings were observed in 29 cases, as either reduced variability (n = 13) or fetal bradycardia (n = 17). All but 3 bradycardias reported occurred during maternal cardiac surgery involving aortic clamping and cardiopulmonary bypass. In 1 case, FHR monitoring was not possible because of a surgical pneumoperitoneum; there was 1 fetal tachycardia associated with maternal pyrexia, and three cases in which FHR monitoring was deemed stable or normal. Three preterm infants were delivered simultaneously at the time of general surgery as a result of FHR abnormalities (at 30, 33, and 34 weeks respectively), 2 as a result of fetal bradycardia and 1 because of protracted reduced variablity.

Conclusion: The evidence for intraoperative fetal monitoring is based on case reports and cases series. Maternal cardiac surgery involving cardiopulmonary bypass commonly results in fetal bradycardia, which may be challenging to interpret. Obstetricians should be aware of FHR pattern changes in response to anesthesia and surgery that do not justify iatrogenic preterm cesarean delivery.