Fetal metabolic adaptations to cardiovascular stress in twin-twin transfusion syndrome

Adverse outcomes in monochorionic twins with amniotic fluid abnormalities without TTTS: A Case-Control study

OBJECTIVE

Monochorionic diamniotic (MCDA) twins with amniotic fluid abnormalities that do not meet criteria for twin-twin transfusion syndrome (TTTS) concern physicians and families. This study aimed to describe the natural history of amniotic fluid abnormalities.

METHODS

In this retrospective case-control study, TTTS screening ultrasounds and clinical records throughout all MCDA twin gestations were reviewed between 2018 and 2022 at a tertiary fetal care center. Twin pairs with normal imaging throughout gestation comprised a control group. Cases with fluid abnormalities were divided into four subgroups: (1) isolated polyhydramnios of one twin, (2) isolated oligohydramnios of one twin, (3) subjective physician concern about fluid discrepancy without objectively abnormal fluid in either twin, (4) or selective fetal growth restriction (sFGR) with any of the above fluid abnormalities. Since the aim was to trend unclear fluid findings, twins who flipped from normal imaging to clear diagnostic criteria for TTTS, selective fetal growth restriction (sFGR), or twin-anemia polycythemia sequence (TAPS) within one scan were excluded. Also excluded were gestations with structural anomalies affecting fluid quantity, higher order multiples, and cases with only one scan available.

RESULTS

Of 737 gestations, 300 were excluded for clear diagnostic findings, 19 had a fetal anomaly impacting fluid, 10 were higher order multiples, and 44 had only one scan. Of the remaining 364, 224 had normal imaging and formed the control group, while 140 had fluid abnormalities not diagnostic for TTTS. Twins with fluid abnormalities developed more TTTS (41 %), TAPS (8 %), new-onset sFGR (11 %), and need for laser (36 % vs 0 %, all p < 0.001). Fetal demise (11 % vs 1 %, p < 0.001) and maternal admissions for fetal surveillance (15 % vs 4 % p = 0.001) were seen more often in cases, who also had an earlier gestational age at delivery (33.1 vs 35.1 weeks, p < 0.001) when compared to controls.

CONCLUSIONS

Amniotic fluid abnormalities that do not yet meet criteria for TTTS should be considered a warning sign in MCDA twin pregnancies. These abnormalities are associated with more complications, fetal intervention, fetal demise, and long hospital stays.

Stage-based recipient and donor outcome in twin-to-twin transfusion syndrome treated by fetoscopic laser surgery using Solomon technique

OBJECTIVE

To evaluate twin survival stratified by Quintero stage in patients with twin-to-twin transfusion syndrome (TTTS) after Solomon laser treatment.

METHODS

This was a single-center study at Johns Hopkins Center for Fetal Therapy, investigating a cohort of consecutive twin pregnancies treated with the Solomon laser technique for TTTS. Preoperative Quintero stage, perioperative characteristics and obstetric factors were investigated in relation to neonatal survival of the recipient and donor twins at discharge. Determinants of twin survival were evaluated using univariate logistic regression and cumulative survival probability analyses.

RESULTS

Of 402 pregnancies with TTTS that underwent Solomon laser treatment, 80 (19.9%) were diagnosed with Quintero Stage-I TTTS, 126 (31.3%) with Stage II, 169 (42.0%) with Stage III and 27 (6.7%) with Stage IV. Post-laser twin anemia polycythemia sequence or recurrent TTTS occurred in 19 (4.7%) patients and 11 (2.7%) required repeat laser surgery. Preterm prelabor rupture of membranes occurred in 150 (37.3%) patients and median gestational age at delivery was 32 + 1 weeks. In 303 (75.4%) patients, both twins were alive at discharge; 67/80 (83.8%) were Stage I, 101/126 (80.2%) were Stage II, 113/169 (66.9%) were Stage III and 22/27 (81.5%) were Stage IV (P = 0.062). Donor twin survival was lower than that of recipients in cases with Stage-III TTTS (118/169 (69.8%) vs 145/169 (85.8%) (χ2 = 26.076, P < 0.0001)). Higher intertwin size discordance and absent or reversed umbilical artery (UA) end-diastolic velocity (EDV) were associated with donor demise (Nagelkerke R2, 0.38; P < 0.001). Overall, spontaneous post-laser donor demise occurred in 53 (39.6%) patients, accounting for the majority of all losses. Cumulative donor survival decreased from 92% to 65% when intertwin size discordance was >30% and to 48% when UA-EDV was absent or reversed (P < 0.001).

CONCLUSIONS

The Solomon laser technique achieves TTTS resolution and double twin survival in a high proportion of cases. Recipient and donor survival is comparable unless there is significant intertwin size discordance and placental dysfunction. This degree of unequal placental sharing, typically found in Stage-III TTTS, is the primary factor preventing double survival due to a higher rate of donor demise. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

Suture Characteristics after Exposure to Amniotic Fluid from an in vitro Model of Fetal Surgery

INTRODUCTION

Suture tensile properties have only been tested in extrauterine environments. Amniotic fluid (AF) is a complex milieu of enzymes and inflammatory factors. This study tested the mechanical properties of sutures with a variety of inherent properties, after exposure to AF from patients with conditions prompting fetal intervention.

METHODS

AF was obtained from 3 patients with twin-twin transfusion syndrome (TTTS), and 3 patients with neural tube defects. Six types of 2-0 sutures were placed on 1.2 N of tension to mimic placement in vivo, and incubated in AF at 37°C (98.6°F). These included ethylene terephthalate (Ethibond), glycomer 631 (V-Loc), poliglecaprone 25 (Monocryl), poly-4-hydroxybutyrate (Monomax), polydioxanone (PDS), and polyglactin 910 (Vicryl). Failure load, stress, strain, and initial modulus were tested after 24 h of incubation and after 4 weeks, and compared with control (unincubated) sutures using t tests, Kruskal-Wallis tests, and stress-strain curves.

RESULTS

Poliglecaprone 25 and polyglactin 910 dissolve more quickly in AF compared to outside the uterus, disintegrating at 4 weeks. Ethylene terephthalate and PDS experienced little change across 4 weeks of incubation. Glycomer 631 and poly-4-hydroxybutyrate exhibited interesting behavior in AF: glycomer 631 became more deformable at 24 h but later regained toughness by 4 weeks, while poly-4-hydroxybutyrate became tougher and in some cases stronger with time in AF. As a class, braided sutures act more like rigid materials, and monofilaments act like deformable plastics.

CONCLUSION

These findings along with other suture characteristics such as ease of handling and availability may inform fetal intervention teams as they optimize procedures in a relatively new surgical field.

Acute Fetal Metabolomic Changes in Twins Undergoing Fetoscopic Surgery for Twin-Twin Transfusion Syndrome

Fetuses undergo major surgical stress as well as fluid shifts secondary to both twin-twin transfusion (TTTS) as well as the fetoscopic surgery for treatment of TTTS. While the pathophysiology of TTTS is understood, the acute metabolic changes that fetuses experience from fetoscopic surgery are not. We sought to evaluate the changes in recipient metabolomic profile secondary to TTTS surgery. Amniotic fluid was collected at the beginning and end of four TTTS surgical cases performed from 12/2022-2/2023. Samples were immediately processed and evaluated via NMR-based Metabolomics Facility protocol. In univariate analysis, 12 metabolites (glucose, lactate, and 10 key amino acids) showed statistically significant changes between the beginning and end of the surgery. Among these, 11 metabolites decreased at the end, while only lactate increased. Supervised oPLS-DA modeling revealed pyruvate and lactate as the two metabolites most impact on the variance between cases, and that 40% of metabolomic changes could be attributed directly to the timing that the sample was taken (i.e., if pre- or postoperatively). These results indicate significant metabolic changes in the recipient twin during fetoscopic surgery for TTTS. These findings of decreased glucose, increased lactate, and decreased amnio acids would indicate increased catabolism during surgery. This study raises questions regarding optimal maternal and fetal nutrition during surgery and if nutritional status could be optimized to further improve twin survival during fetoscopic surgery.