# Fetal Heart Rate Patterns in Monochorionic Twins Following Acute Twin-Twin Transfusion

Authors: Shunji Suzuki; Nao Iwasaki; Shuichi Ono; Miwa Igarashi; Tomoaki Murata
Journal: Obstetrics and Gynecology International
 (2009)

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## Abstract

Background. We present here 2 cases of acute twin-twin transfusion occurred during vaginal labor in monochorionic-diamniotic twin pregnancies. Case. Fetal heart rate tracings showed tachycardia in the donor twin in the first case, while they showed reassuring patterns in both twins in the second case. Conclusion. These differences in changes of fetal heart rate in the donor twins following acute twin-twin transfusion may be resulted from the differences in amount of transfusion and elapsed time.


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## Body

## 1. Introduction

Acute twin-twin transfusion is a problem of short duration and might
result in a difference in hemoglobin concentration at birth between the donor
and the recipient twins without the pathologic findings of chronic twin-twin
transfusion syndrome such as oligohydramnios/polyhydramnios [1, 2]. Acute shifts of blood from one twin to the
other twin are thought to be resulted from blood-pressure differences due to
uterine contractions or changes in fetal positions [1–3].  We present here 2 cases of acute twin-twin
transfusion occurred during vaginal labor in monochorionic-diamniotic twin
pregnancies.  Fetal heart rate tracings
showed tachycardia in the donor twin in the first case, while they showed
reassuring patterns in both twins in the second case.


## 2. Case 1

A 26-year-old gravida 2 para 1 had labor induced by intravenous
administration of oxytocin at 39 weeks’ gestation.  Her monochorionic-diamniotic twin pregnancy
had progressed uneventfully based on weekly ultrasonic examinations.  The amniotic fluid pockets and estimated
fetal growth of both twins were normal at 5 days before the labor.  On admission, her body temperature was36.2°C and blood pressure was 124/78 mmHg.  During
the latent phase of labor, fetal heart rate tracings showed reassuring patterns
in both twins.  At this time, the
base lines of twins A and B were 150 and 150 bpm, respectively, as shown in
Figure 1.  When the cervix was dilated 8 cm, the membranes of twin A were ruptured.
Within 10–20 minutes, the fetal heart rate of twin A was increased to 170–180 bpm with repeated variable decelerations as shown in Figure 2.  Thirty minutes later, a 3138 g male infant (twin
A) with Apgar scores of 8 and 9 at 1 and 5 minutes, respectively, was born.  His hemoglobin concentration was 11.4 g/dL
(normal: 13–22 g/dL) with reticulocyte counts of 2.1% (normal: <7%).  Six minutes after the delivery of the first
twin, a 2720 g male infant (twin B), was delivered
spontaneously with Apgar scores of 9 and 9 at 1 and 5 minutes,
respectively.  His hemoglobin concentration
was 24.0 g/dL.  He required intravenous
infusion of 10% glucose for correction of polycythemia.  The placenta was confirmed as monochorionic
with 2 large superficial arterio-arterial anastomoses and 2 deep arterio-venous
anastomoses.  The growth and hemoglobin
differences between the twins were 13% and 12.6 g/dL, respectively.Figure 1
Fetal heart rate
tracings during labor the latent phase of labor showing reassuring fetal heart
rate patterns in both twins.Figure 2
Fetal heart rate
tracings during the active phase of labor showing the increased baseline of
heart rate with variable decelerations in twin A.


## 3. Case 2

A 37-year-old gravida 2 para 1 had labor induced by intravenous
administration of oxytocin at 38 weeks’ gestation.  Her monochorionic-diamniotic twin pregnancy
had progressed uneventfully based on weekly ultrasonic examinations.  The amniotic fluid pockets and estimated
fetal growth of both twins were normal at 4 days before the labor.  On admission, her body temperature was36.6°C and blood pressure was 136/80 mmHg.  During the labor, fetal heart rate tracings
showed reassuring patterns in both twins.
The base lines of twins A and B were 140 and 145 bpm, respectively.  A 2248 g female infant (twin A) with Apgar
scores of 8 and 9 at 1 and 5 minutes, respectively, was born without
difficulty.  Her hemoglobin concentration
was 11.2 g/dL with reticulocyte counts of 4.7%.
Five minutes after the delivery of the first twin, the second twin, a
2078 g female infant (twin B), was delivered spontaneously with
Apgar scores of 9 and 10 at 1 and 5 minutes, respectively.  His hemoglobin concentration was 24.8 g/dL.  She required intravenous infusion
of 10% glucose for correction of polycythemia.
The placenta was confirmed as monochorionic with 3 large superficial
arterio-arterial anastomoses and 2 deep arterio-venous anastomoses.  The growth and hemoglobin differences between
the twins were 7.6% and 13.6 g/dL, respectively.


## 4. Comment

Although the multiple placental
vascular anastomoses such as these 2 cases are nearly always present in
monochorionic twin pregnancies, the incidence of acute twin-twin transfusion
has been reported to be rare [1–6]. For
example, we have encountered only these 2 cases of acute twin-twin transfusion
(1.5%) in 132 monochorionic-diamniotic twin vaginal labors during the recent
5-year period.Acute twin-twin transfusion is a diagnosisper exclusionem which has been thought to be mediated through large
superficial low-resistance arterio-arterial or veno-venous anastomoses [1–4]. The possible criteria for acute twin-twin transfusion
are: (a) difference in hemoglobin concentration at birth >5 g/dL between
the twins, (b) the absence of pathologic findings of chronic twin-twin
transfusion syndrome such as ologohydramniso/polyhydramnios, and (c) the
absence of findings of twin anemia-polycythemia sequence such as high reticulocyte
count in the donor twin [1–4]. The
current 2 cases were suggested as having acute twin-twin transfusion based on
their clinical findings, although it is not possible to prove these diagnoses
absolutely conclusively.In these cases, we observed 2 patterns of fetal hart rate tracings in
the donor twins.  One showed tachycardia,
and the other showed normocardia.  In some animals, there have been some observations in various fetal cardiovascular responses to fetal blood loss [7, 8].  Yoshihara et al. [7] observed that fetal heart
rate did not change measurably during 40 ml per 2 hours of fetal hemorrhage in pregnant goats
near term.  Brace and Cheung [8] observed
that the heart rate in fetal sheep was elevated by an average of 2 bpm at 3 to 5
hours after the fetal hemorrhage of 30% of their initial blood volume although it did not change
measurably during the
hemorrhage.  These changes have been
observed to be due to the changes in fetal plasma renin activity, arginine
vasopressin, and norepinephrine following fetal blood loss [7, 8]. Therefore, the differences in changes of fetal heart rate in the
donor twins of acute twin-twin transfusion may be resulted from the differences
in amount of transfusion and elapsed time.In the
current 2 cases, there were no measurable changes in fetal heart rate
tracings of the recipient
twins following acute twin-twin transfusion.
In some previous reports [1–4, 9], in addition, there have not been any significant comments
about the fetal heart rate patterns in the recipient twins following acute
twin-twin transfusion.
Therefore, we expect the elucidation of heart rate patterns in the
recipient twins by accumulation of the same case reports.



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*Source: 498530-2009-04-06.xml*