Peter Kovacs, MD, PhD


April 20, 2006


A patient with premature ovarian failure underwent ovum donation and intracytoplasmic sperm injection. Now she has 3 separate gestational sacs. One of the sacs contains 2 embryos (8 weeks crown rump length [CRL] measurement); another sac contains 1 embryo (8 weeks CRL) embryo; and one of the sacs is empty. What is the best way to proceed? Should one of the embryos be terminated? If so, which one should be chosen? Also, which week of gestation is most suitable for the procedure?

Kahraman Ulker, MD

Response from Peter Kovacs, MD, PhD

Response from  Peter Kovacs, MD, PhD 
Visiting Clinical Instructor, Department of Ob/Gyn, Albert Einstein College of Medicine, Bronx, NY; Research and Scientific Coordinator, Kaali Institute, IVF Center, Budapest, Hungary


A multifetal pregnancy is an undesired outcome of assisted reproductive technology (ART). It is associated with increased maternal morbidity (eg, hypertension, diabetes, and operative delivery) and mortality and fetal/neonatal morbidity (eg, preterm delivery, growth retardation, low birth weight, and complications as a result of prematurity) and mortality.

During ART, one has several opportunities to avoid multiple gestations. First, the patients at risk (eg, young patients, good response to stimulation, and availability of several top-quality embryos during in vitro fertilization [IVF]) need to be identified. Controlled ovarian hyperstimulation cycles with multifollicular development can be canceled or converted to IVF. Fewer -- and now more often single -- embryos can be transferred in patients at high risk. A singleton pregnancy may be the desired outcome in cases of certain maternal medical problems, the presence of uterine anomaly, pregnancy following uterine surgery, or for socioeconomic reasons.

As a result of recent efforts, the number of high-order multiple gestations has declined, but still a significant proportion of ART cycles result in twin pregnancies. Most twin pregnancies are dizygotic following IVF; only about 0.4% are monozygotic. The various types of twins (monozygotic vs dizygotic, monoamniotic vs diamniotic) are associated with different antepartum problems. Monozygotic twins further complicate the clinical scenario because they may result in high-order multiple gestations even when a limited number of embryos have been transferred.

When more embryos implant than desired, one faces a difficult dilemma. Should the pregnancy continue and expose the patient to the risks associated with potential prematurity, or should some intervention be offered that reduces the number of fetuses although it also has inherent risks? Some of multifetal pregnancies reduce spontaneously, as the result of miscarriages. If this does not occur, multifetal pregnancy reduction can be offered. Several factors are considered when the decision about the reduction is made. The type of multifetal pregnancy (whether it is monochorionic or dichorionic), any sign of fetal abnormality, results of genetic testing (when available), and technical aspects (which sac can be reached easier with less trauma) are all taken into account. The timing of the reduction is also important. On the one hand, earlier reduction when the uterus is less "irritable" is associated with less risk. On the other hand, a significant proportion of early pregnancies are miscarried spontaneously. One should wait until the fetal heartbeat can be detected (7- 8 weeks), because the risk for a spontaneous pregnancy loss is low after that. Obviously the results of genetic testing, if required, should be available before the decision is made, and the reduction should be scheduled toward the end of the first trimester.

The procedure is usually performed by injecting potassium chloride into the fetal circulation. This could be a problem, however, when vascular anastomosis is present between the fetuses. This is the case with monochorionic twins. The immediate demise of the noninjected twin has been reported with monochorionic twins. Under such circumstances, occlusion of the cord (coagulation or laser ablation) can be attempted, although the risk for premature of rupture of the membranes is higher with this approach.

The case in the question describes an empty sac, a sac with a single embryo, and a third sac with 2 embryos inside. A triplet pregnancy is associated with high risk for perinatal morbidity/mortality; therefore, fetal reduction should be offered to the patient. A monochorionic twin pregnancy is associated with more risks later during the pregnancy as well (twin-to-twin transfusion syndrome, fetal demise, anomalies, and cord entanglement). Therefore, from a technical point of view, it makes more sense to reduce it rather than the singleton. This obviously requires a thorough discussion with the patient. The couple needs to understand what risks the procedure carries (in which the generally reported risk for pregnancy loss is between 5% and 10%), and what risks a multifetal, especially a monochorionic, pregnancy carries.


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