Key result
Uncomplicated MCDA twins show ~58% higher cord blood BNP at birth versus singletons.
Why the study?
Cardiovascular dysfunction occurs in complicated monochorionic diamniotic pregnancies, but whether hemodynamic changes occur in uncomplicated monochorionic diamniotic twins was unknown.
Does uncomplicated monochorionic diamniotic twin pregnancy alter fetal cardiac structure, function, and cord blood BNP levels at delivery compared with gestational age-matched low-risk singleton pregnancy?
Cohort (n=300)
Yes
Does uncomplicated monochorionic diamniotic twin pregnancy alter fetal cardiac structure, function, and cord blood BNP levels at delivery compared with gestational age-matched low-risk singleton pregnancy?
Uncomplicated monochorionic diamniotic twin fetuses have normal overall cardiac z-scores allowing the use of singleton nomograms, but exhibit adaptive atrial dilatation, concentric ventricular hypertrophy, enhanced longitudinal systolic function, and elevated birth BNP levels due to in utero volume and pressure overload.
Answers are grounded in this paper and cite their sources.
Supports use of singleton nomograms in uncomplicated MCDA twins; leaves open whether BNP elevation and hypertrophy affect postnatal outcomes.
Cardiovascular dysfunction has been reported in complicated monochorionic diamniotic (MCDA) pregnancies; however, little is known whether hemodynamic changes occur in uncomplicated MCDA twins. A prospective observational study was conducted including 100 uncomplicated MCDA twins matched by gestational age to 200 low-risk singletons. Echocardiography was performed at 26–30 weeks gestation and cord blood B-type natriuretic peptide (BNP) was measured at delivery. In both groups, z-scores for echocardiographic parameters were within normal ranges; however the monochorionic group had larger atrial areas (mean (standard deviation) right atria-to-heart ratio: 17.0 (2) vs. 15.9 (1); p = 0.018; left atria-to-heart ratio: 17.0 (3) vs. 15.8 (2); p < 0.001) and signs of concentric hypertrophy (right relative wall thickness: 0.66 (0.12) vs. 0.56 (0.11); p < 0.001; left relative wall thickness: 0.69 (0.14) vs. 0.58 (0.12); p < 0.001). Longitudinal function was increased in twins, leading to higher tricuspid annular plane systolic excursion (6.9 mm (0.9) vs. 5.9 mm (0.7); p < 0.001) and mitral annular plane systolic excursion (4.9 mm (0.8) vs. 4.4 mm (1.1); p < 0.001. BNP levels at birth were also higher in MCDA twins (median [interquartile range]: 20.81 pg/mL [16.69–34.01] vs. 13.14 pg/mL [9.17–19.84]; p < 0.001). Thus, uncomplicated MCDA fetuses have normal cardiac shape and function, but signs of cardiac adaptation were identified by echocardiographic and biochemical parameters, when compared with singletons.
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Torres et al. (2020) conducted a cohort in Uncomplicated monochorionic diamniotic (MCDA) twin pregnancies (n=300). Uncomplicated monochorionic diamniotic (MCDA) twin pregnancy vs. Gestational age-matched low-risk singleton pregnancy was evaluated on Cord blood B-type natriuretic peptide (BNP) at delivery (pg/mL) (p=<0.001). Uncomplicated MCDA twin fetuses exhibited higher cord blood BNP levels at birth (20.81 vs 13.14 pg/mL; p<0.001), larger atrial areas, and concentric hypertrophy compared with singletons.
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