DÄ internationalArchive50/2010Inconsistent Terminology

Correspondence

Inconsistent Terminology

Dtsch Arztebl Int 2010; 107(50): 902. DOI: 10.3238/arztebl.2010.0902a

Zollner, U; Rehn, M; Dietl, J

LNSLNS

We noticed some inconsistencies in the terminology used in the review article by Dudenhausen et al, which we wish to clarify. In twin pregnancies, a distinction is made—depending on placentation and zygosity—between dichorionic (two placentas) and monochorionic (one placenta) pregnancies and dizygous (non-identical/biovular) and monozygous (identical) twins.

We make a plea for using the terms zygosity and chorionicity correctly.

To monitor the pregnancy and antenatal care, determining zygosity is irrelevant and sonographically impossible (in dichorionic placentation); it is exclusively chorionicity that is important. A monochorionic twin pregnancy can develop only from monozygous twins, whereas a dichorionic pregnancy can, as Dudenhausen and Maier mentioned, develop from two different fertilized ova (dizygous) or a single ovum (monozygous) that has divided at a very early stage.

The statement “monozygous twins have a thin membrane, dizygous twins have a thick membrane” is therefore incorrect. Monochorionic twins have a thin membrane, and dichorionic twins (which may be monozygous or dizygous) have a thick membrane. Diagnostic evaluation by ultrasonography can determine the zygosity with any degree of certainty therefore only in monochorionic twins, not in dichorionic twins (exception: if the twins are not the same sex).

Further, we wish to point out that fetofetal transfusion syndrome (FFTS) with a stuck twin is not mild FFTS (Figure 2), but according to the criteria set out by Quintero et al. (1), it is severe FFTS.

DOI: 10.3238/arztebl.2010.0902a

PD Dr. med. Ursula Zollner

Dr. med. Monika Rehn

Prof. Dr. med. Johannes Dietl

Universitäts-Frauenklinik Würzburg

Josef-Schneider-Str. 4

97080 Würzburg, Germany

E-Mail: zollner_u@klinik.uni-wuerzburg.de

1.
Quintero RA, Morales WJ, Allen MH, Bornick PW, Johnson PK,
Kruger M: Staging of twin-twin transfusion syndrome. J Perinatol 1999; 19(8): 550–5. MEDLINE
2.
Dudenhausen JW, Maier RF: Perinatal problems in multiple births. Dtsch Arztebl Int 2010; 107(38): 663–8. VOLLTEXT
1.Quintero RA, Morales WJ, Allen MH, Bornick PW, Johnson PK,
Kruger M: Staging of twin-twin transfusion syndrome. J Perinatol 1999; 19(8): 550–5. MEDLINE
2.Dudenhausen JW, Maier RF: Perinatal problems in multiple births. Dtsch Arztebl Int 2010; 107(38): 663–8. VOLLTEXT