1. Reproducibility and accuracy of 2D and 3D ultrasound parameters in the prediction of birthweight in pregnancies with low serum PAPP-A
- Author
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Thurlwell, Zoe, Johnstone, Edward, and Myers, Jenny
- Subjects
Reproducibility of 2D and 3D ultrasound ,Accuracy of 2D and 3D ultrasound ,fractional thigh volume ,Tvol ,Fetal growth ,PAPP-A ,Pregnancy associated plasma protein A - Abstract
Background: Currently used methods to estimate fetal size in the third trimester, are suboptimal in detecting fetal growth restriction. Inclusion of a 3D ultrasound fractional thigh volume within an estimated fetal weight model may provide a more accurate estimate of fetal size. Low first trimester maternal serum Pregnancy associated plasma protein-A (PAPP-A < 0.415MoM / 5th centile) is associated with Small for gestational age (SGA) and placental dysfunction (PD) and this group provides an enriched population to assess the value of fractional thigh volume estimation. SGA is currently defined using birthweight and heavily influenced by skeletal growth in EFW models. Hypothesis, Aims and objectives: Longitudinal fractional thigh volume could provide a more reproducible and accurate assessment of fetal size and growth trajectory in pregnancies complicated by low maternal serum PAPP-A. Methods: New Ultrasound Parameters in Pregnancy 2 (NUPs2) was a prospective, longitudinal cohort study of 112 women with low maternal serum PAPP-A. Measurements of 2D fetal biometry and fractional thigh volume (Tvol) were obtained at 6 weekly scan intervals from 15 weeks until 38 weeks' gestation. Automated volume measurements were obtained using 4D view software (GE Healthcare). Reproducibility and accuracy were assessed using intraclass correlation coefficients (ICC) and BlandAltman Plots. Fetal growth, incorporating Tvol as a measure of non-skeletal growth, was compared in pregnancies associated with and without a low PAPP-A. In addition, multi-level linear regression analyses were used to interrogate the impact of low PAPPA on fetal growth, following adjustment for known important covariates. Results: Tvol measurements were highly reproducible (ICC > 0.99) and have a low measurement error especially in the third trimester. Inclusion of Tvol within an estimated fetal weight (EFW) model provided a more accurate in utero-assessment when compared to birthweight than any 2D EFW model (BPD-AC-Tvol ICC 0.96 [0.93 – 0.98] Versus Hadlock HC-AC-FL ICC 0.93 [0.85 – 0.96]). Findings from this thesis suggest that pregnancies affected by low PAPP-A are associated with a reduction in skeletal growth across gestation compared with a non-low PAPP-A. The reduction in skeletal growth remained consistent for low PAPP-A with and without PD. Reduction of skeletal and adipose growth was also shown in those with PD and low PAPP-A. Discussion: The addition of Tvol, especially in the third trimester, improved the accuracy and reproducibility of EFW models. While within the low PAPP-A cohort, a novel growth pattern of reduced skeletal growth was identified. A subgroup of fetuses within the low PAPP-A cohort were identified as SGA; One cohort with reduced skeletal mass without PD, the other with PD, likely leading to a nutritional deficit leading to a smaller overall size. Therefore, women with low PAPP-A without PD may benefit from alternative scan surveillance, antenatal care and timing of delivery from current practice.
- Published
- 2021