A new study published in Pregnancy found that fewer than 1% of serial fetal monitoring tests in high-risk pregnancies ended with a non-reassuring result, highlighting the importance of tailoring repeated testing to patients’ specific risk factors.
The study did not specifically evaluate fetal and neonatal alloimmune thrombocytopenia (FNAIT), but its findings may offer broader context for families undergoing repeated monitoring during high-risk pregnancies. In FNAIT, decisions about fetal surveillance are often individualized based on each pregnancy’s risk factors.
In the study, patients first received a non-stress test (NST), which monitors the baby’s heart rate. A reactive NST is reassuring, while a nonreactive NST does not necessarily mean something is wrong, but signals that more evaluation is needed. Patients with nonreactive NSTs then received a biophysical profile (BPP), an ultrasound-based test used to assess fetal well-being. Among 19,034 NSTs, 87.3% were reactive, and 96.4% of follow-up BPPs were reassuring.
The research was conducted as a retrospective cohort study of singleton pregnancies that underwent serial antenatal testing at 28 weeks’ gestation or later. The analysis included patients tested across four sites in an academic health system between January 2022 and May 2023.
Repeated fetal monitoring is recommended for many high-risk pregnancy concerns, but some reasons for surveillance may be more likely than others to lead to abnormal results. In this study, researchers focused mainly on abnormal BPP results, the follow-up test used when an NST was nonreactive.
The researchers also looked separately at patients who were referred for surveillance because of only one risk factor, rather than multiple pregnancy complications. In this group, only 0.4% of visits resulted in an abnormal or unclear BPP, and post-term pregnancy was the only indication linked to abnormal BPP results.
Although several testing indications were linked to nonreactive NSTs, only fetal growth restriction, vaginal bleeding and post-term pregnancy were associated with abnormal BPP results. Chronic hypertension, obesity and hypertensive disorders of pregnancy were also linked to nonreactive NSTs, but were not associated with abnormal BPP results.
Read more about FNAIT testing and diagnosis
“As presenting for serial fetal testing remains a significant barrier for many patients, these data can support data-informed patient counseling and help clinicians prioritize those at greatest risk,” the authors wrote.
The study had several limitations. Because researchers did not evaluate later pregnancy or newborn outcomes, the findings cannot show whether abnormal results reflected true fetal risk or whether different monitoring schedules would change outcomes.
Sign up here to get the latest news, perspectives, and information about FNAIT sent directly to your inbox. Registration is free and only takes a minute.
