**Conflict of interest**

techniques, they are associated with a lower technical failure rate (13 vs. 35%), lower rate of preterm birth or rupture of membranes before 32 weeks (23 vs. 58%), and higher rate of

**Figure 11.** Upper image: Acardiac twin with retrograde flow in the umbilical cord. Lower image: Normal recipient twin.

There are some doubts about the optimal time to do the treatment. Performing any procedure before the obliteration of the coelomic cavity increases the risk of talipes and miscarriage [136]; therefore, most of the authors perform the intervention between 13 and 16 weeks [124]. In one study in which the median gestational age at intervention (intrafetal laser ablation) was 13.2 weeks, there was a 41% mortality rate in the first 72 h after the procedure; therefore, surgery before 13 weeks of gestation should be avoided [136]. Some studies showed that expectant management could be offered in special cases. Jelin et al. [125] found a 100% survival when the acardiac twin had less than 50% of the pump twin's weight. Other studies suggested that discordance between crown-rump length of the pump twin and upper pole-rump length of the TRAP twin could be potential predictors of pregnancy

The optimal approach should be an early diagnosis and a proper parental counseling and an intrafetal intervention, by laser or RFA in 13–16 weeks. The expectant management could be

considered if the TRAP twin is smaller (about half the size) than the pump twin.

clinical success (77 vs. 50%) [135].

142 Multiple Pregnancy - New Challenges

Adapted from ultrasound Obstet Gynecol. Pagani et al. [124].

outcome [137].

There are no conflicts of interest in this chapter.
