Fetoscopy and Risk of Iatrogenic Preterm Premature Rupture of Membranes: Not as High as It May Seem (in Experienced Hands)

delivery. While we are not aware of any sufficiently large clinical series reporting the perinatal outcome of fetuses with lower urinary tract obstruction managed expectantly, there is abundant information on other types of malformation. For instance, neural tube defects present rates of preterm delivery of up to 38% [3] . Along the same lines, congenital diaphragmatic hernia, which was not analyzed in the review by Beck et al. [1] , has been reported to be associated with up to 29% of PPROM in pregnancies managed expectantly [4] . With these numbers in mind, the 40–47% [4, 5] reported for cases managed with tracheal occlusion indeed suggests a clear impact of fetoscopy, but not as impressively high as it may seem without any baseline comparison. A second important message of Beck et al.’s review [1] is that the diameter of the fetoscopic instrument is an independent predictor of the risk of PPROM. This is interesting information which had not been previously demonstrated. Again, however, the statement requires some qualification in the sense that the analysis included a wide range of diameters (0.8–5 mm). Thus, while it is certainly true that 1-mm instruments are associated with a substantially lower risk of PPROM than those of 5 mm, the impact of changes in fractions of mm could possibly be negligible. This is relevant because in clinical practice we may easily be tempted to reduce the outer diameter of the trocar. Indeed, going from 10 to 8 French may proIn this issue of Fetal and Diagnostic Therapy , Beck et al. [1] publish an interesting systematic review on the factors influencing the risk of preterm premature rupture of membranes (PPROM) in fetoscopy. While this is a difficult task considering the scarcity of consistent information among published papers, the authors manage to extract some very interesting conclusions. The manuscript provides important messages, which add to the body of knowledge in the field of fetoscopy. However, these messages must be interpreted properly in order to be translated into clinical practice and patient counseling. Firstly, the analysis confirms previously reported figures that fetoscopy is associated with a relatively high rate of PPROM, up to 30%, defined as that occurring earlier than the 37th week of gestation. However, the correct interpretation of these numbers is that, after all, fetoscopy is possibly not associated with a huge increase in the rate of PPROM. Indeed, we must remember that we are dealing with abnormal pregnancies. Twin monochorionic pregnancies are the clearest example of this. In a multicenter prospective study including over 200 monochorionic twin pregnancies, baseline risk of spontaneous PPROM in those not complicated by twin-to-twin transfusion syndrome was 25% [2] . In the case of shunting for urinary tract obstruction, it is possible that the increase is more important. However, fetal malformations are associated with an increased risk of PPROM and preterm Published online: January 31, 2012