Contribution of fetal weight estimation in twin pregnancies: a prospective study

Introduction

Ultrasonography is an essential tool in the management of twin pregnancies. Fetal weight estimation is useful to anticipate neonatal care in case of prematurity, growth restriction or growth discordance.

Objective 

The aim of this study was to evaluate the accuracy of ultrasound fetal weight prediction in twin pregnancies.

Methods

Fifty patients with an ultrasonography within 4 days before birth were studied. Estimated fetal weight (EFW) was compared with birth weight (BW). Fetal hypotrophyand growthdiscordance superior or equal to 25 % between the first and the second twin were recorded.

Results 

Absolute differences between EFW and BW were similar for both twins (155 g [72–337.5] for T1 and 150g [100–266.5] for T2).
Mean absolute percentage error was 7.7% (2.5-14.76gr) for T1 and7.55% (3.37-11.85gr) for T2.
Mean absolute percentage error was superior to 10% for 20% of T1 and 18% of T2with no significant difference.
Chorionicity, gestational age as well as fetal presentation did not influence fetal weight estimation
T1 correlation coefficient is 0.87; T2 correlation coefficient is 0.89.
PN de J1 = 415,57+ 0,846*PFE de J1
PN de J2 = 65,68+0,963*PFE de J2
Ultrasonography in the diagnosis of hypotrophy had a sensitivity of 90.32%, a specificity of 78.94%, a positive predictive value (PPV) of 83.5% and a negative predictive value (NPV) of 87.5%. For the prediction of growth discordance, sensitivity was 76.9%, specificity 81.8%, PPV 50% and NPV 93.5%.

Conclusion 

Fetal weight can be accurately predicted in twin pregnancies.
The contribution of ultrasonography in the diagnosis of hypotrophyand growth discordance is mainly due to a high NPV.

Keywords

Twin pregnancies; weight estimation