In this prospective observational cohort study, we pioneered the use of a nomogram to predict the prognosis of patients with FGR. The nomogram, based on abnormal UA Doppler, abnormal MCA Doppler and log10(sFlt-1/PlGF), was verified to have a discriminatory ability (AUC) of 0.79 (95% CI 0.65–0.93) in predicting APO development. Furthermore, the nomogram was validated to have good capability of calibration and clinical application. The results showed that combining ultrasonic and maternal serum biochemical indicators could effectively predict the APO development in pregnancies complicated by FGR, facilitating clinicians to ensure personalized and precise counseling, efficient allocation of resources and optimization of clinical management.
Earlier studies of FGR, retrospective and prospective, have also attempted to look for predictive indexes of APO. There was only one retrospective study which reported multiple factors involving high-risk maternal factors and ultrasound indicators[22]. By comparison, our study was characterized by the prospective design and dataset of perinatal registry data and hospital records. Thanks to this, the information of predictors was acquired at the time of FGR diagnosis, which in our cohort was on average three weeks prior to delivery.
In general, a single factor such as biometric measurement or growth trajectory alone, is not adequately identify the risk of adverse perinatal outcomes. Previous studies suggested that cerebroplacental (CPR) and umbilicocerebral (UCR) ratios on their own are poor prognostic predictors of APO (AUC 0.44 and 0.56, respectively)[23, 24]. Using a slow growth trajectory as stand-alone criterion for FGR was reported not to be associated with a higher risk of APO in a low-risk population[25]. The large Pregnancy Outcome Prediction (POP) study found that EFW < 10th percentile was associated with the risk of neonatal morbidity only when the AC growth velocity was in the lowest decile[26]. In this context, the sFlt-1/PlGF ratio could be used to complement ultrasound examinations. As reported by a small size study, a sFlt-1/PlGF ratio ≥ 86.2 resulted in maximum detection of pregnancies at risk of APO in a cohort of 34 women with FGR diagnosed at < 34 weeks[27]. In the present study, the analysis of only FGR cases provided an opportunity to reconsider the factors that could be integrated into the prognostic nomogram. The nomogram integrates multiple factors, including ultrasonic and serum markers, into a quantitative model and has been shown to perform better (AUC 0.79 and 0.75 in the training and validation cohorts respectively) than some conventional indexes, such as abnormal UA and MCA Doppler.
Previous studies have applied screening models of multiple factors to the general population and demonstrated the ability to identify small-for-gestational-age (SGA) neonates, without much success at delineating those at risk of APO[16, 17, 28]. For example, a competing-risks model, based on maternal factors and biophysical (UtA-PI) and biochemical (PlGF) markers at 11–13 weeks’ gestation, was reported to be effective for prediction of FGR (defined as birth weight < 3rd percentile) in women with preeclampsia[28]. For obstetricians, it is more important to identify the constitutionally small fetus from one who is pathologically growth restricted and at risk for postnatal complications. In our study, the main outcome of APO was the same as the previously reported in the large prospective study[19]. Therefore, it is necessary to provide individualized consultation and surveillance for pregnant women with a nomogram total score > 5.01, as their fetuses may run a higher risk of developing APO in the future.
Our study has important clinical implications as it has demonstrated promising potential value in predicting FGR patients’ prognosis. The nomogram has shown good performance for detecting FGR pregnancies at a higher risk of APO, which require more frequent scans, but also cases at a lower risk that could benefit from a less strict surveillance protocol. As suggested by our results, FGR patients with total points > 5.01 should be closely monitored and appropriate timing of delivery. In pregnancies with total points < 5.01, on the contrary, scan intervals could be extended so that the number of fetal ultrasounds could be reduced to lower parental anxiety and lessen the burden on the healthcare system. Due to our observational study is preliminary, further randomized clinical trials are required to establish a more efficient predictive model for guiding FGR management.
We acknowledge some limitations of this study. First, our study is based on an observational cohort, so the Doppler measurements and biomarker testing were performed as part of routine clinical care rather than as blinded randomized controlled trials (RCTs), which could increase the potential for bias. Second, the small number of cases could introduce some uncertainty in the screening factors, which was illustrated by 95% CI, thus being likely to limit the external validity of our findings. Larger cohorts or RCTs are expected in the future. Finally, some perinatal outcomes had a low incidence, such as bronchopulmonary dysplasia and cystic periventricular leukomalacia, and only 27 cases were severe FGR (ultrasonographic EFW or AC below the 3rd percentile), so the results should be interpreted with caution.
In conclusion, the newly developed nomogram is simple to use and capable of predicting the prognosis in patients with FGR. The combination of ultrasonic and maternal serum biochemical indicators can be applied to identifying FGR with a high probability of APO development, which facilitates patients to benefit from early triage and more intensive monitoring. More well-designed randomized clinical trials are required.