Background
Triplet pregnancies are associated with higher fetal morbidity and mortality risk such as to be delivered by cesarean at < 29 weeks of gestation and to have > or = 1 infants die as well as life-threatening maternal complications such as preterm premature rupture of membranes, preeclampsia, eclampsia, toxemia, placental abruption, excessive bleeding, to require tocolysis, and postpartum hemorrhage [
1,
2]. The incidence of MCDA triplet births is rare compared to other types of triplet pregnancies [
3], and the incidence of spontaneous triplet pregnancies is approximately 1/10,000 [
4]. However, triplet births have increased due to older maternal age at conception and the increased use of assisted reproductive technology, such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), gamete intrafallopian transfer (GIFT), and intracervical insemination (ICI) [
5]. The proportion of triplet pregnancies conceived using assisted reproductive technology versus naturally has increased in recent years (42.5% vs. 17.7%) [
5,
6].
Trichorionic triamniotic (TCTA), dichorionic triamniotic (DCTA), and monochorionic triamniotic (MCTA) triplets are the most common types of triplet pregnancies [
7]. Monochorionic diamniotic (MCDA) and dichorionic diamniotic (DCDA) triplet pregnancies are extremely rare. Fennessy et al. [
8] reported that 58% (31/53), 32% (17/53), 8% (4/53), and 2% (1/53) of triplet pregnancies are TCTA, DCTA, MCTA, and DCDA, respectively.
Due to special chorionic and amniotic properties in MCDA triplets, cord entanglement between two fetuses can increase the incidence of perinatal morbidity and mortality in MCDA triplets. Nearly
10 papers [
7,
9‐
18] related to MCDA triplet pregnancies have been published so far, and the majority have been case reports. However, there is no consensus-based guidance for the perinatal management of MCDA triplet pregnancies. MCDA triplet pregnancies can have good perinatal outcomes with regular prenatal care. Therefore, the antenatal diagnosis, evaluation, and management of MCDA triplet pregnancies are worth further discussion.
We report three cases of MCDA triplet pregnancies at West China Second University Hospital, a tertiary referral center in west China, between January 2012 and December 2017. In addition, we evaluate the perinatal management and outcomes of these MCDA triplets. In our study, the case with regular and intensive prenatal care had a good perinatal outcome, and the case with irregular perinatal care had poor outcomes.
Discussion
Triplet pregnancies are associated with an increased risk of maternal complications, including gestational diabetes mellitus, gestational hypertension, preeclampsia, eclampsia, toxemia, intrahepatic cholestasis of pregnancy, anemia, preterm premature rupture of membranes, placental abruption, excessive bleeding, to require tocolysis, postpartum hemorrhage, and abortion [
1,
19‐
21].
Such pregnancies are also related to poorer neonatal outcomes, such as preterm birth (delivered by cesarean at < 29 weeks of gestation), intrauterine growth restriction, low birth weight, congenital anomalies, fetal death, and to have > or = 1 infants die, neurological disability and other short-and long-term disabilities [
1,
8,
22]. Besides, the fetal loss rate of triplets is nearly 25% [
23].
The prevalence rate of triplet gestations in the United States and Canada has been approximately 154 and 84 per 100,000 live births, respectively, in the last few years [
24]. Moreover, at our hospital, the prevalence rate of triplets was 11.14/10,000, and the proportion of MCDA triplet pregnancies was 4.41% (3/68) between January 2012 and December 2017.
The placentation of monochorionic is characterized by placental vascular anastomoses and thus inter fetal transfusion [
23]. Chorionicity contributes greatly to adverse perinatal outcomes, and monochorionicity is associated with a higher rate of perinatal complications [
5]. The rates of fetal death after 22 weeks and neonatal death in MCTA, DCTA, and TCTA triplet pregnancies are 5.3, 3.2, and 2.1%, respectively [
25]. In Japan, the perinatal mortality rates of monochorionic, dichorionic, trichorionic triplet deliveries are 12.5, 4.4, and 2.0%, respectively [
26]. The incidence of preterm birth before 32 weeks in triplet pregnancies is 24.1-fold higher than that in singleton pregnancies and 3.3-fold higher than that in twin pregnancies [
27]. Nearly 14% of triplets are delivered before 30 weeks, and 61% of triplets are born before 34 weeks [
26]. Compared with singleton pregnancies, triplet pregnancies are nearly four times more expensive [
27]. Therefore, triplet pregnancies are not recommended due to higher fetal morbidity and mortality.
When a triplet pregnancy is diagnosed, management options, including continuing the pregnancy with expectant treatment or elective reduction to twins or a singleton, should be discussed with the couple [
28,
29]. Elective reduction to twins or a singleton requires occlusion of the umbilical vessel by laser photocoagulation, bipolar electrocoagulation and radiofrequency ablation [
30].
When a single embryo splits between 4 and 8 days after fertilization, an MCDA twin pregnancy occurs, and MCTA triplets occur if one of the twins further splits before the 8th day after fertilization [
31]. MCDA triplets are extremely rare and can be diagnosed by ultrasonography. Cord entanglement between two fetuses can increase the incidence of perinatal morbidity and mortality in MCDA triplets. Due to the rarity of MCDA triplet pregnancies, there is no standard management protocol.
To the best of our knowledge, there have been nearly
10 papers [
7,
9‐
18] related to MCDA triplet pregnancies published in English, and the results are summarized in Table
1.
Table 1The character of the included study
| 41 | 3 | 2 | not mention | 13 | 28 | CS | No | Selective feticide of the conjoined twins was conducted at 16 gestational weeks, the normal triplet died at 28 weeks weighing 1010 g | Yes |
| 33 | 3 | 1 | not mention | 17 | 31 | CS | No | Spontaneous cessation of blood flow to the acardiac fetus at 23 weeks, another two fetuses were alive and well. | Yes |
| 32 | 1 | 0 | Yes | 25–26 | 30 | CS | No | Three healthy triplets | Yes |
| 22 | 1 | 0 | Yes | 11 | Termination of pregnancy | No | / | not mention |
| 20 | 1 | 0 | Yes | 21 | Termination of pregnancy | No | / | No |
| 38 | 1 | 0 | No (ART) | 12 + 3 | 17 | VD | No | selective feticide of the conjoined fetuses, then the membrane ruptured the day after the feticide and inevitable abortion | No |
| 34 | 1 | 0 | Yes | 12 | 35 | CS | No | Three healthy newborns | Yes |
| 34 | 1 | 0 | No (ART) | 8 + 2 | 33 | CS | decreased platelet count | Three healthy and survival infants | Yes |
| 41 | 1 | 0 | No (ART) | 25 | 30 + 5 | CS | severe hyponatraemia associated with pre-eclampsia | Three healthy triplets | not mention |
| 30 | 2 | 1 | not mention | Histology of the placenta | 27 + 6 | CS | No | A live pump twin and two conjoined acardiac TRAP recipients | No |
| 25 | 1 | 0 | not mention | 34+ | 34+ | CS | respiratory distress | One alive male fetus and two female dead fetus | No |
Our cases |
No. 1 | 28 | 3 | 0 | Yes | 13 + 4 | 32 + 5 | CS | No | Three healthy and survival newborns | Yes |
No. 2 | 27 | 3 | 0 | Yes | 18 + 5 | 32 + 3 | CS | No | Three healthy and survival infants | Yes |
No. 3 | 20 | 2 | 0 | Yes | 12+ | 28 + 3 | CS | lung infection and heart failure | Three survival male babies, the parents give up further treatment | Yes |
Most of the cases were diagnosed by ultrasound in the first trimester or early second trimester, especially in Suizu's report [
10], where MCDA triplet pregnancies were diagnosed around 9 weeks. Four cases of conjoined twins in MCDA triplet pregnancies have been reported [
12,
14,
16,
18]. In May’s study, the MCDA triplets consisted of two conjoined acardiac twins and one surviving fetus with a normal heart. The live newborn was delivered by cesarean section at 27 + 6 weeks and was discharged from the NICU after a 14.5-week stay [
12]. Two cases were reported of MCDA triplets in which the conjoined twins underwent selective feticide at 16 gestational weeks; however, in one case, intrauterine demise of the normal triplet occurred at 28 weeks [
14], and in the other case, the membranes ruptured the day after the procedure, resulting in an inevitable abortion [
16]. Sellami’s case report [
18] describes xipho-omphalopagus conjoined twins in an MCDA triplet pregnancy that was terminated at 21 weeks. Sepulveda [
15] reported an acardiac fetus complicating an MCDA triplet pregnancy. The blood flow of the acardiac fetus spontaneously ceased at 23 weeks, while the other two fetuses remained alive and well. Four cases of MCDA triplet pregnancies with regular prenatal care had good perinatal outcomes. These 12 healthy infants remained healthy without any other major complications during follow-up after birth [
7,
10,
11,
17]. One case with no regular antenatal care was misdiagnosed as a twin pregnancy, and MCDA triplets were established during the cesarean section; one live fetus and two dead fetuses were delivered at 34+ gestational weeks [
13]. Detailed information on these cases is provided in Table
1.
In our study, the cases with careful and regular prenatal care had good perinatal outcomes, and six healthy babies remained well without any short-or long-term abnormalities. Conversely, the case (case 3) with no regular antenatal care during pregnancy had a poor outcome.
It is true that some of the conditions discussed from cited papers couldn’t be prevented even with regular prenatal care. However, from this data in Table
1, we can see most of the cases were diagnosed by ultrasound in the first trimester or early second trimester and conjoined twins were common in MCDA triplets. Besides, we also can see that for most MCDA triplet pregnancies with regular prenatal care had good perinatal outcomes expect some uncontrollable and unavoidable factors.
Conclusion
Taking together the above-published articles and our cases, we conclude that intensive prenatal care by a multidisciplinary team is important for obtaining a better perinatal outcome. In addition, umbilical cord entanglement between two fetuses sharing the same amniotic sac was found in most of our MCDA triplets, which can increase the incidence of perinatal morbidity and mortality. MCDA triplet pregnancies with cord entanglement can be successfully managed by early diagnosis, regular antenatal care, close prenatal monitoring, sufficient communication, and elective delivery.
Therefore, it is very important for women with an MCDA triplet pregnancy to obtain intensive prenatal care, which can help obstetricians adjust perinatal evaluations and management strategies in a timely manner to avoid adverse perinatal complications. Weekly ultrasounds are recommended after 28 gestational weeks. It is better for women with MCDA triplet pregnancies to be admitted to the hospital at 28–30 weeks and complete fetal lung maturation. A histopathological examination of the placenta to confirm the chorionicity and amnionicity of an MCDA triplet pregnancy is necessary after delivery.
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