Multifetal Pregnancy Reduction – First or Second Trimester

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The incidence of multifetal pregnancies has increased dramatically over the past two decades, mainly because of the widespread use of ovulation induction agents and assisted reproduction techniques. These techniques have been a matter of concern since twin and higher order pregnancies have long been associated with an increased risk of maternal complications as well as a high prevalence of prenatal and neonatal morbidity and mortality [1-5].

In the USA, between 1973 and 1990, twin births increased from 1 in 55 births to 1 in 40, and the rate of triplets and higher rose from 1 in 3323 to 1 in 1343 [6].

The procedure of multifetal pregnancy reduction has, in recent years, become both clinically and ethically accepted as a therapeutic option in pregnancies with four or more fetuses ([7-16] and in multifetal pregnancies in which one or more of the fetuses has congenital abnormalities [8,17]. In cases of triplet gestations, however, this option remains controversial [7, 13,14, 16, 18-20]. Reports of the improving outcome of triplet pregnancies [21,22], the failure to demonstrate an improvement in the outcome of triplet pregnancies reduced to twins as compared with those managed expectantly [18,19], and the procedure-related risk of losing the entire pregnancy [13,24] have complicated the clinical and ethical discussion surrounding this procedure in triplet gestations.

Consideration of the clinical options and the ethical issues involved in the management of triplet or higher order gestations should include the probability of achieving a successful pregnancy outcome if an expectant management policy is undertaken. Dickey et al. [24] reported that when three viable embryos were diagnosed at first trimester ultrasound, the probability of delivering triplets and twins was 68.4 and 21%, respectively. This outcome was influenced by the chronological age of the mother.

The pregnancy loss subsequent to fetal reduction has been reported as ranging from O to 40% [25]. However, in recent reports the reduction of triplets to twins resulted in a fairly consistent fetal loss of 6-8% [10,13,16, 19].

Several methods of multifetal pregnancy reduction have been proposed. Some authors have used transcervical aspiration of the gestational sac [26,27]. This method, however, was thought to be associated with an increased incidence of fetal loss due to infection caused by introduction of bacteria from the cervix, or due to cervical incompetence brought about by cervical dilatation [12].

Fetal reduction very early in gestation (6 to 8 weeks) by the transvaginal puncture and embryo aspiration also reported with fairly good pregnancy outcome. However, this method might have some theoretical limitations, such as, (1) using general anesthesia, (2) the possibility of spontaneous fetal reduction at this stage of gestation, (3) the inability to perform early fetal screening, such as, nuchal translucency test, which is done later on in pregnancy, and (4) the possibility of increasing infections. Multifetal pregnancy reduction using intrathoracic injection of potassium chloride, by both the transabdominal and the transvaginal approaches, has been reported [7,8, 10, 13-16,23,26,27]. No method has yet been proven to be superior to the others [14, 16].

Although several techniques ofMPR have been reported, however, the most popular is the intrathoracic inj action of potassium chloride by the transabdominal approach at 10-12 weeks gestation. It has been reported that MPR performed at later weeks of pregnancy may be accompanied by increased risk of pregnancy loss IfMPR, performed at around 14 weeks gestation, is not accompanied by greater risk to the pregnancy, it is logical to perform a detailed ultrasonographic fetal anomaly scan prior to the reduction This will allow the reduction to be performed more selectively and will decrease the chance of delivery of a chromosomal or structurally abnormal fetus.

References:

References

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