Reproducibility and Accuracy of 2D and 3D ultrasound parameters in the prediction of birthweight in pregnancies with low serum PAPP-A

  • Zoe Thurlwell

Student thesis: Doctor of Medicine


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 0.99) 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.
Date of Award31 Dec 2021
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorEdward Johnstone (Supervisor) & Jenny Myers (Supervisor)


  • 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

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