Predictive performance for placental dysfunction related stillbirth of the competing risks model for small‐for‐gestational‐age fetuses

Abstract

Objectives: To examine the predictive performance for placental dysfunction related stillbirths of the competing risks model for small-for-gestational-age (SGA) fetuses based on a combination of maternal risk factors, estimated fetal weight (EFW) and uterine artery pulsatility index (UtA-PI); and second, to compare the performance of this model with that of a stillbirth-specific model using the same biomarkers and with the Royal College of Obstetricians and Gynecologists (RCOG) guideline for the investigation and management of the SGA fetus.Design: Prospective observational study. Setting: Two UK maternity hospitals.Population: A total of 131 514 women with singleton pregnancies attending for routine ultrasound examination at 19-24 weeks of gestation. Methods:The predictive performance for stillbirth achieved by three models was compared.Main Outcome Measure: Placental dysfunction related stillbirth.Results: At 10% false-positive rate, the competing risks model predicted 59%, 66% and 71% of placental dysfunction related stillbirths, at any gestation, at <37 weeks and at <32 weeks, respectively, which were similar to the respective figures of 62%, 70% and 73% for the stillbirth-specific model. At a screen positive rate of 21.8%, as defined by the RCOG guideline, the competing risks model predicted 71%, 76% and 79% of placental dysfunction related stillbirths at any gestation, at <37 weeks and at <32 weeks, respectively, and the respective figures for the RCOG guideline were 40%, 44% and 42%. Conclusion:The predictive performance for placental dysfunction related stillbirths by the competing risks model for SGA was similar to that of the stillbirth-specific model and superior to that of the RCOG guideline.

Competing‐risks model for pre‐eclampsia and adverse pregnancy outcomes

“…Although not quantified previously, it is perhaps unsurprising that the 35-37 weeks' competing-risks model for PE identifies risk for a broader range of pregnancy complications. Our competing-risks model for PE (at multiple gestational ages) 4 shares many predictors with our models for SGA 25,26 and stillbirth 27 , based on shared underlying placental pathophysiology 28 . The association of PE risk with both Cesarean section and NNU admission likely reflects diminishing placental reserve near or at term; term NNU admission most commonly results from perinatal asphyxia 29 .…”

Incidence of stillbirth: effect of deprivation

“…The first stage is screening for PE at 11-13 weeks' gestation and treatment of the high-risk group with aspirin; this is effective in the prevention of preterm PE as well as early SGA in the absence of PE [18][19][20][21][22][23] . The second stage is screening during the routine mid-trimester scan by a combination of maternal risk factors, estimated fetal weight and uterine artery pulsatility index, which identifies a high-risk group that contains a high proportion of placental dysfunction-related stillbirths that occur at 24-37 weeks' gestation; close monitoring of these pregnancies for early diagnosis of SGA fetuses may prevent at least some of such stillbirths by defining the best monitoring approach and timing of delivery 5,24,25 . The third stage is routine ultrasound examination at 36 weeks' gestation because screening at midgestation provides poor prediction of stillbirth at term; the detection rate for term SGA by assessment at 36 weeks' gestation is twice as high as with screening at midgestation 26,27 .…”

“…We have reported previously that the risk for stillbirth has a U‐shaped relationship with maternal age and increases with increasing body mass index, black race, smoking, medical history of chronic hypertension and diabetes mellitus, and a history of previous stillbirth 5,6 . Studies from countries with populations that are of predominantly white race have consistently reported that, in women of black race, the incidence of stillbirth is 2‐fold higher than in white women; the risk for South or East Asians is usually not different from that in white women 6 .…”

“…Stillbirths can be broadly classified into antenatal and intrapartum and are also subdivided into those thought to be the consequence of impaired placentation and those due to other causes or that are unexplained. The rationale for categorizing stillbirths according to the likely underlying cause is that antenatal intervention and preventive strategies can be undertaken more effectively [2][3][4][5] .…”

Competing‐risks model for prediction of small‐for‐gestational‐age neonate at 36 weeks' gestation

“…The Royal College of Obstetricians and Gynaecologists guideline recommends using a risk-scoring system to identify the high-risk group 9 . We have demonstrated recently that this method, implemented at 22 weeks' gestation, has poor performance for the identification of a SGA neonate and stillbirth 10,11 . There is evidence that prediction of SGA is improved when, first, routine third-trimester biometry is used instead of selective sonography based on maternal risk factors and serial measurements of symphysis-fundus height 12 , second, EFW is used instead of fetal abdominal circumference 8,13 and, third, the scan is carried out at 36 weeks rather than at 32 weeks' gestation 8,14,15 .…”