MPR for monochorionic diamniotic twins
Most of the literature on MPR from twin to singleton gestations reports on intrathoracic potassium chloride injection used in dichorionic diamniotic twins.
MPR in monochorionic diamniotic twins is reserved in the United States for monochorionic pregnancies in which there are severe fetal anomalies, severe growth restriction, or other significant complications. It is performed in such cases around 20 weeks gestation. However, given the significant risks of monochorionic twin pregnancies, we also have been offering MPR electively and earlier in pregnancy. While many modalities of intrafetal cord occlusion exist, RFA at the cord insertion site into the fetal abdomen is our preferred technique.
In our retrospective review of 315 monochorionic diamniotic twin gestations, the 14 patients who had RFA electively had no pregnancy losses and a significantly lower rate of preterm birth at less than 37-weeks gestation, compared with 301 ongoing monochorionic diamniotic twin pregnancies (29% vs. 76%).5 Reduction with RFA, performed at a mean gestational age of 15 weeks, also eliminated the risks unique to monochorionic twins, such as twin-to-twin transfusion syndrome and twin-anemia polycythemia sequence. (Of the ongoing twin gestations, 12% required medically indicated RFA, fetoscopic laser ablation, and/or amnioreduction; 4% had unintended loss of one fetus; and 4% had unintended loss of both fetuses before 24 weeks’ gestation. Fewer than 70% of the ongoing twin gestations had none of the significant adverse outcomes unique to monochorionic twins.)
Interestingly, there were still a couple of cases of fetal growth restriction in patients who underwent elective MPR – a rate higher than that seen in singleton gestations – most likely because of the early timing of the procedure.
Our numbers of MPRs in this review were small, but the data offer at least preliminary evidence that planned elective RFA before 17 weeks gestation may be offered to patients who do not want to assume the risks of monochorionic diamniotic twin pregnancies.
Counseling in twin pregnancies
We perform thorough, early assessments of fetal anatomy in our twin pregnancies, and we undertake thorough medical and obstetrical histories to uncover birth complications or medical conditions that would increase risks of preeclampsia, preterm birth, fetal growth restriction, and other complications.
Because monochorionic gestations are at particularly high risk for heart defects, we also routinely perform fetal echocardiography in these pregnancies.
Genetic testing is offered to all twin pregnancies, and as mentioned above, we especially counsel those considering MPR that such testing provides useful information.
Patients are made aware of the option of MPR and receive nondirective counseling. It is the patient’s choice. We recognize that elective termination is a controversial procedure, but we believe that the option of MPR should be available to patients who want to improve outcomes for their pregnancy.
When anomalies are discovered and selective termination is chosen, we usually try to perform MPR as early as possible. After 16 weeks, we’ve found, the rate of pregnancy loss increases slightly.
Dr. Stone is the Ellen and Howard C. Katz Chairman’s Chair, and Dr. DeBolt is a clinical fellow in maternal-fetal medicine, in the Raquel and Jaime Gilinski Department of Obstetrics, Gynecology, and Reproductive Science at the Icahn School of Medicine at Mount Sinai, New York.
References
1. Martin JA and Osterman MJK. National Center of Health Statistics. NCHS Data Brief, 2019;no 351.
2. Manasa GR et al. Am J Obstet Gynecol MFM 2021;3:100447.
3. Vieira LA et al. Am J. Obstet Gynecol. 2019;221:253.e1-8.
4. Di Mascio et al. Ultrasound Obstet Gynecol 2020 Nov;56(5):647-55.
5. Ferrara L et al. Am J Obstet Gynecol. 2008 Oct;199(4):408.e1-4.