Reduced fetal growth velocity precedes antepartum fetal death

Abstract

Objectives: To determine whether decreased fetal growth velocity precedes antepartum fetal death and to evaluate whether fetal growth velocity is a better predictor of antepartum fetal death compared to a single fetal biometric measurement at the last available ultrasound scan prior to diagnosis of demise.

Methods: This was a retrospective, longitudinal study of 4285 singleton pregnancies in African-American women who underwent at least two fetal ultrasound examinations between 14 and 32 weeks of gestation and delivered a liveborn neonate (controls; n = 4262) or experienced antepartum fetal death (cases; n = 23). Fetal death was defined as death diagnosed at ≥ 20 weeks of gestation and confirmed by ultrasound examination. Exclusion criteria included congenital anomaly, birth at < 20 weeks of gestation, multiple gestation and intrapartum fetal death. The ultrasound examination performed at the time of fetal demise was not included in the analysis. Percentiles for estimated fetal weight (EFW) and individual biometric parameters were determined according to the Hadlock and Perinatology Research Branch/Eunice Kennedy Shriver National Institute of Child Health and Human Development (PRB/NICHD) fetal growth standards. Fetal growth velocity was defined as the slope of the regression line of the measurement percentiles as a function of gestational age based on two or more measurements in each pregnancy.

Results: Cases had significantly lower growth velocities of EFW (P < 0.001) and of fetal head circumference, biparietal diameter, abdominal circumference and femur length (all P < 0.05) compared to controls, according to the PRB/NICHD and Hadlock growth standards. Fetuses with EFW growth velocity < 10^th percentile of the controls had a 9.4-fold and an 11.2-fold increased risk of antepartum death, based on the Hadlock and customized PRB/NICHD standards, respectively. At a 10% false-positive rate, the sensitivity of EFW growth velocity for predicting antepartum fetal death was 56.5%, compared to 26.1% for a single EFW percentile evaluation at the last available ultrasound examination, according to the customized PRB/NICHD standard.

Conclusions: Given that 74% of antepartum fetal death cases were not diagnosed as small-for-gestational age (EFW < 10^th percentile) at the last ultrasound examination when the fetuses were alive, alternative approaches are needed to improve detection of fetuses at risk of fetal death. Longitudinal sonographic evaluation to determine growth velocity doubles the sensitivity for prediction of antepartum fetal death compared to a single EFW measurement at the last available ultrasound examination, yet the performance is still suboptimal. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Keywords: abdominal circumference; biparietal diameter; customized growth standard; head circumference; small-for-gestational age; stillbirth.

Figure 1.. Longitudinal estimated fetal weight (EFW) percentiles as a function of gestational age.

The figure shows EFW percentiles according to the customized PRB/NICHD growth standard (A), and the Hadlock growth standard (B) for 28 cases of fetal death. There was a downward trend of EFW percentiles with advancing gestation. Only 28.6% (8/28) of cases had an EFW <10^th percentile at the last scan, using either of the two fetal growth standards. The red horizontal line shows the 10^th percentile line.

Figure 2.. Estimated fetal weight (EFW) percentiles at the first and last ultrasound examinations.

The figure shows EFW percentiles before 32 weeks in the study group according to the PRB/NICHD growth standard (A), and the Hadlock growth standard (B). There was no significant difference in the median percentile between cases and controls at the first ultrasound examination. However, the EFW percentiles of cases were lower than those of controls at the last ultrasound examination. IQR: Interquartile range.

Figure 3.. Differences in estimated fetal weight (EFW) percentile velocity between cases and controls.

The figure shows EFW percentile velocity according to the PRB/NICHD standard (A), and the Hadlock standard (B). EFW velocity was calculated as the change in the EFW percentile per week by fitting a linear regression model to the percentile values of each patient. Cases had significantly lower EFW velocity compared to controls, according to the two growth standards.

Figure 4.. Receiver Operating Characteristic (ROC) curve for the prediction of antepartum fetal death by a low growth velocity.

The ROC curves are constructed from EFW percentile velocity data based on the PRB/NICHD growth standard, and the Hadlock growth standards. AUC: area under the ROC curve. 95% confidence intervals are provided.

Figure 5.. Prediction of antepartum fetal death by non-customized percentiles velocity.

ROC curves were obtained based on percentile velocity of estimated fetal weight (EFW), fetal head circumference (HC), biparietal diameter (BPD), abdominal circumference (AC), and femur length (FL) based on non-customized PRB/NICHD (A) and Hadlock (B) standards. AUC: area under the ROC curve. 95% confidence intervals are provided.