Gestational age-specific reference ranges for amniotic fluid assessment in monochorionic diamniotic twin pregnancies

Authors

  • P. DeKoninck,

    1. Fetal Medicine Unit, Department of Obstetrics and Gynecology, University Hospitals Leuven and Research Unit Fetus, Placenta and Neonate, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
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  • J. Deprest,

    1. Fetal Medicine Unit, Department of Obstetrics and Gynecology, University Hospitals Leuven and Research Unit Fetus, Placenta and Neonate, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
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  • P. Lewi,

    1. Fetal Medicine Unit, Department of Obstetrics and Gynecology, University Hospitals Leuven and Research Unit Fetus, Placenta and Neonate, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
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  • J. Richter,

    1. Fetal Medicine Unit, Department of Obstetrics and Gynecology, University Hospitals Leuven and Research Unit Fetus, Placenta and Neonate, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
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  • S. Galjaard,

    1. Fetal Medicine Unit, Department of Obstetrics and Gynecology, University Hospitals Leuven and Research Unit Fetus, Placenta and Neonate, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
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  • J. Van Keirsbilck,

    1. Fetal Medicine Unit, Department of Obstetrics and Gynecology, University Hospitals Leuven and Research Unit Fetus, Placenta and Neonate, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
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  • K. Van Calsteren,

    1. Fetal Medicine Unit, Department of Obstetrics and Gynecology, University Hospitals Leuven and Research Unit Fetus, Placenta and Neonate, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
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  • L. Lewi

    Corresponding author
    • Fetal Medicine Unit, Department of Obstetrics and Gynecology, University Hospitals Leuven and Research Unit Fetus, Placenta and Neonate, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
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Correspondence to: Dr L. Lewi, Department of Obstetrics and Gynecology, University Hospitals Leuven; Department of Development and Regeneration, KU Leuven, Herestraat 49, B-3000 Leuven, Belgium (e-mail: liesbeth.lewi@uzleuven.be)

ABSTRACT

Objectives

To establish gestational age-specific reference ranges for amniotic fluid measurements in monochorionic diamniotic twin pregnancies, to compare them with previously reported singleton and twin reference ranges and to examine the rationale for using a gestational age-dependent cut-off to define polyhydramnios in twin–twin transfusion syndrome, as is the practice in most European centers.

Methods

We retrospectively evaluated amniotic fluid volume in 32 monochorionic diamniotic twin pregnancies that were followed longitudinally at 2-week intervals from the first trimester until birth. Amniotic fluid volume was assessed by measuring the deepest vertical pocket in both amniotic sacs. We used multilevel modeling to estimate the gestational age-specific reference ranges for deepest vertical pocket measurements.

Results

Based on 429 observations in 64 fetuses, we constructed gestational age-specific reference ranges from 11 weeks until term. The deepest pocket increased from the first trimester to reach a maximum at 26 weeks, followed by a gradual decrease towards term. Measurements between 18 and 28 weeks were comparable to those in singleton pregnancies. However, before 18 weeks values were higher, whereas after 28 weeks they were lower, as compared to singleton references.

Conclusion

In monochorionic twin pregnancies, the deepest vertical pocket is a gestational age-dependent measurement. Therefore, a gestational age-dependent definition of polyhydramnios in twin–twin transfusion syndrome, as used by most European centers, seems a logical approach. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.

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