Multiple pregnancies significantly increase the incidence of severe fetal and maternal complications. It is difficult to decide whether MFPR or not while considering the risk of abortion.The aim of this research was to compare the pregnancy and obstetric outcomes of different reduction tactics and anticipation management in DCTA and TCTA pregnancies.
DCTA pregnancies have many associated risks, such as premature delivery, selective growth restriction, and fetal malformations. Monochorionic twins are associated with single placental bed vascular anastomoses, such as TTTS and selective intrauterine growth restriction [16–17]. These adverse pregnancy and obstetric outcomes have led to search for a favorable fetal reduction strategy for reducing the occurrence of the aforementioned adverse events. However, although MFPR can reduce the premature delivery rate, the miscarriage rate will increase correspondingly. Therefore, no consensus exists on whether MFPR should be performed and the optimal number of fetal reductions in DCTA pregnancies[18]. Some research has shown that MFPR to singleton in DCTA may improve the pregnancy outcomes and positively alter gestational week, related to infant mortality and disability[9, 18,19–21].
A systematic review of different treatment strategies in DCTA suggested that anticipation management is a reasonable option When survival rates are prioritized.Conversely, if minimizing the rate of severe premature delivery is the top priority,the best desirable choice is to reduce the number of fetuses [20]. The research of Chaveeva et al. supports the conclusion that embryo reduction increases the miscarriage rate but reduces the premature delivery rate in DCTA pregnancy [21]. However, our research found that the complete miscarriage rate was significantly reduced from 29.41 to 2.63% in DCTA reduction to singleton than DCTA-anticipation management group. In addition, there was no significant difference in the complete miscarriage rate between TCTA reduction and anticipation management groups. And in this study, the complete miscarriage rate after reduction was lower than previous addressed. This finding demonstrates that DCTA reduction to singleton may be an effective choice during the 6–8 weeks gestational period.
Because of the vascular anastomosis between monochorionic twins [22], when reducing one of the monochorionic twins, more caution should be undertaken while performing fetal reduction surgery, and the complete miscarriage rate of TCTA- anticipation management was significantly lower than that of DCTA-anticipation management in our study.
There were significant differences between the subgroups of participants who underwent MFPR to singleton compared to those who choose MFPR to twin or anticipation management in DCTA and TCTA pregnancies, which shows that DCTA reduction to singleton improved pregnancy and obstetric outcomes by obviously reducing the risks of premature delivery and LBW,and obviously raising gestational week and average birth weight in DCTA and TCTA pregnancies. Thus, we didn’t advocate anticipation management for DCTA pregnancy.
Potassium chloride injection is not recommended for monochorionic pregnancy because the remaining fetus can be embolized by the drug through vascular anastomosis in the common placenta[23]. However, the laser technique of intrafetal interstitia to remove one monochorionic twin can also imperil the remaining twin [24]. Chaveeva et al. reported 61 pregnant women with DCTA whose pregancies were reduced to dichorionic twins pregnancy by intrafetal laser ablation;although 3% of cases of miscarriage occurred after reduction, nearly half of the cases occurred within two weeks after reduction [15]. Other studies show that the mechanical method of intracardiac puncture and aspiration is an effective and feasible MFPR method for reducing adverse pregnancy outcomes, including those in monochorionic twin pregnancies [25–28]. Therefore, we adopted the mechanical method of intracardiac puncture and aspiration to reduce the fetus during the 6–8 weeks gestational period.
The miscarriage rate of DCTA-anticipation management group was obviously higher than DCTA reduction to singleton group, although the mechanism of miscarriage is not clear. Some researchers think the relative lack of adequate uterine cavity and blood provision is related to spontaneous fetal reduction in multifetal pregnancy [29]. However, we also found that pregnancy loss occurs after embryo reduction in DCTA and TCTA pregnancies. Compared TCTA reduction to twin with DCTA reduction to twin group, TCTA reduction to twin group would obtain the proportion of two babies is significantly higher than that of DCTA reduction to twin group. This dramatically higher singleton survival rate and dramatically lower twin survival rate in DCTA pregrancy is consistent with the findings of Li et al [26]. According to some studies, the related mechanism of miscarriage caused by fetal reduction in DCTA may be considered as follows: firstly, injuries and infections caused by fetal reduction surgery in cases where miscarriage occurred within 2 weeks of fetal reduction. Secondly, the necrotic embryonic placental tissue causing the inflammation reaction is reabsorbed, which could cause miscarriage several weeks or months after fetal reduction [30, 31]. Therefore, when considering reducing the complications of pregnancy and adverse obstetric outcomes and choosing to reduce fetuses to dichorionic twins in DCTA pregnancies, couples should be informed about the higher risk of pregnancy loss. There was no significant difference in cesarean section rate and the percentage of boy between the three subgroups in DCTA and TCTA pregnancies. The main reason why there is no difference in the rate of cesarean section may be due to human factors rather than medical needs.
Due to the unique characteristics of monochorionic twin pregnancies in terms of the placental structure, some studies conclude that monochorionic twins have dramatically worse outcomes than dichorionic twins [24, 32–33]. This may be attributable to the complications associated with monochorionic twins, including TTTS, TAPS, and SIGR, which are detrimental to maternal and fetal health. Liu et al.'s study shows that the pregnancy and obstetric outcomes of DCTA-monochorionic twin pregnancies are relatively worse than those retaining a single fetus but without statistical difference. It is concluded that compared with reducing one fetus in monochorionic twins, reduction with a separate placenta might be an acceptable reduction strategy with a relatively lower miscarriage rate, despite the potential risks to monochorionic twins[19]. However, this research found that the complete miscarriage rate of the DCTA reduction to twin group is slightly higher than that of the DCTA reduction to singleton group, but there is no significant difference. Therefore, regarding the choice of DCTA to twin pregnancy, we must weigh the pros and cons and solicit the choice of couples, informing patients of the risks and benefits of reduction to one or two or anticipation management.
This was a single-center retrospective comparative study, and some of the statistically insignificant results may be due to the limited number of patients in some subgroups.The Eligible patients are not randomly assigned to each group, so the results of the study may have some deviations. Due to different wishes and internal factors of the family,and ethical considerations, some couples may choose to undergo MFPR or not, and this research is unlikely to be suitable for randomized controlled trials. Some of the data were collected through telephonic interviews with women who had been pregnant many years before thereby the data could be prone to recall bias.Some of the strengths of our study i nclude the relatively abundant reduction data, an extended research time frame, strict inclusion criteria, and detailed statistical methods. All reduction operations were performed by several highly skilled doctors in our center, thereby preventing significant differences in surgical results.