Contribution of fetal growth restriction to stillbirth in twin compared to singleton gestations.

Alicia Martínez-Varea1, Josep Domenech2, SmritiPrasad3, Asma Khalil3

1 Department of Obstetrics and Gynaecology, La Fe University and Polytechnic Hospital, Valencia, Spain.

2 Department of Economics and Social Sciences, UniversitatPolitecnica de Valencia, Valencia, Spain.

3 Fetal Medicine Unit, St George's University Hospitals NHS Foundation Trust, London, United Kingdom. 

INTRODUCTION

The objectives of this study were:

We also compared the association between FGR and stillbirth in twin pregnancies, according to the use of twin compared to singleton reference standards.

MATERIALS AND METHODS

This was a retrospective cohort study of pregnancies receiving obstetric care and delivering at St George's Hospital. 

All pregnancies from June 1999-December 2022 were included. Exclusion criteria included deficient data regarding gestational age at birth, miscarriage or livebirth ≤23+6 weeks, and termination of pregnancy. FGR and small for gestational age (SGA) were defined as birthweight <5th and <10th centile, respectively. The four study groups were early and late stillbirths in singleton and multiple pregnancies. Logistic regression assessed potential associations between FGR and stillbirth.

RESULTS

Among 96,166 singleton pregnancies, 507 (0.53%) were stillborn. Of 3,989 fetuses from multiple pregnancies, 61 (1.53%) were stillborn.

FGR and SGA were both risk factors for stillbirth in singleton pregnancies (OR 8.67 [95%CI 7.26−10.34] and 6.31 [5.29−7.52], respectively). Similarly, FGR and SGA were strong risk factors for stillbirth in multiple pregnancies (OR 23.77 [13.44−42.03]) and 20.26 [11.17−36.75]). 

In singletons, 59.8% of early stillbirths were SGA, and 44.7% of late stillbirths were SGA. FGR was a stronger risk factor for early stillbirth among singleton pregnancies (OR early13.32 [CI 10.32−17.20] vs (OR late stillbirth 5.61 [4.27−7.37], p<0.001). In multiple pregnancies, FGR was also a stronger risk factor for early stillbirth (OR early 37.04 [15.33−89.52] vs OR late stillbirth 22.92 [7.87−66.75], p<0.001). 

In multiple pregnancies, a greater proportion of fetuses were diagnosed as SGA when the singleton compared to the twin-specific chart was used (49.3% 11.1%). FGR was a stronger risk factor for stillbirth when diagnosed by twin compared with singleton charts (OR 23.77 [13.44−42.03] vs 5.97 [3.21−11.08], p=0.042). Interestingly, FGR was a stronger risk factor for early stillbirth when diagnosed with twin compared to singleton charts (OR 37.04 [15.33−89.52] vs OR 5.78 [2.48−13.45], p=0.029). 

CONCLUSIONS

In multiple pregnancies, FGR is a stronger risk factor for stillbirth than in singletons, in particular for early stillbirth. FGR diagnosed using twin charts is a stronger risk factor for stillbirth than FGR diagnosed using singleton charts.