A conditional standard for the customized fetal growth trajectory in twin pregnancy.

BACKGROUND: The difference in the birth weights between twins and singletons grows with advancing gestation. Although many fetal weight standards based on ultrasonographic measurements have been created for tracking fetal growth in twin pregnancies, their applicability to other groups is limited by the fact that they are population specific. OBJECTIVE: This study aimed to generate conditional centiles for growth assessment of twin fetuses and to compare them with other population-based growth standards for singleton and twin fetuses. STUDY DESIGN: This was a retrospective, longitudinal study of ultrasound-based estimated fetal weight data of normal twin fetuses delivered after 34 weeks of gestation. Linear mixed effects models that adjusted for maternal characteristics, fetal gender, and chorionicity were used to evaluate the relationship between estimated fetal weight and gestational age. The estimated fetal weight reference values were calculated using conditional centile based on the estimated fetal weight at an earlier gestational age. To compare our results with previous studies, fetal growth curves were generated using a formula we created that included maternal characteristics and the estimated fetal weight at 24 weeks of gestation in these studies. In a subgroup analysis of our low-risk twin babies born at full term, we calculated the number of fetuses who were reclassified as being in the bottom 10th percentile using each of the previous population-based standard. RESULTS: A total of 2644 ultrasounds with a median of 4 scans per fetus from 572 twin pregnancies were included in this analysis. In the cohort, 36% of the fetuses were monochorionic. Maternal age, body mass index, and the interaction between fetal gender and chorionicity were significantly associated with estimated fetal weight. The predicted growth curves matched the growth standard for twins. In our low-risk group, when the singleton standard was used, the incidence of estimated fetal weight <10th percentile was above 20% from gestational week 24 to 38, and this incidence varied when reclassified using other population-based twin standards. CONCLUSION: This conditional growth chart was specifically designed to assess fetal growth in twin pregnancies, but it is generalizable to other populations.

Ablative effect of the interstitial laser setting in the human placental model.

AIM: To assess the impact of laser power and time on interstitial ablation generated by neodymium-doped yttrium aluminium garnet (Nd:YAG) and diode laser in the human placental model. METHODS: The experiment was carried out in a simulation model of interstitial laser ablation on ex-vivo placental tissue. One-hundred and forty-four pieces of fresh placentae were interstitially ablated with Nd:YAG or diode laser at various power (15, 20, 25, 30 W)-time (5, 10, 15 s) combinations. The ablation tissues were evaluated using both sonographic and histopathologic measurements. RESULTS: Laser generator, power, and time significantly affected the ablation size (p < 0.001). The coagulation zone continuously increased with extending time at the power of 15, 20, and 25 W. When adjusting to the power of 30 W, increased time from 10 to 15 s did not induce the larger coagulation diameter. The maximal diameter was obtained at the laser power of 20 W for 15 s. The ablation from the diode laser was greater than that from Nd:YAG laser. The sonographic evaluation overestimated the ablation size by an average of 24%. CONCLUSION: Diode laser destroys greater tissue than Nd:YAG laser. Different power settings of interstitial laser ablation produce diverse patterns of correlation between laser time and coagulation size.

Reference values for fetal Doppler-based cardiocirculatory indices in monochorionic-diamniotic twin pregnancy.

BACKGROUND: Placental anastomoses in monochorionic diamniotic (MCDA) twin pregnancy have a major impact on fetal circulation. This study was designed to define reference ranges of cardiac and vascular Doppler indices in MCDA twin pregnancies. METHODS: This cross-sectional study included 442 uncomplicated MCDA twin fetuses undergoing Doppler ultrasonography at 18-35 weeks of gestation. Left and right myocardial performance index (LV-MPI, RV-MPI), E/A ratio of atrioventricular valves, pulsatility indices of umbilical artery, middle cerebral artery (MCA), and ductus venosus (DV), cerebroplacental ratio, peak systolic velocity of MCA, S/a ratio of DV, and early diastolic filling time of ductus venosus (DV-E) were evaluated under standardized settings. The equation models between Doppler indices and gestational age (GA) were fitted. After adjustment for GA, the correlations between MPI and fetal heart rate (FHR), and between MPI and DV indices were analyzed. RESULTS: Estimated centiles of Doppler indices were derived as a function of GA, being distinct in values from those of singletons. There was no correlation between GA-adjusted MPI and FHR. DV-E was inversely related to LV-MPI. CONCLUSIONS: MCDA twins showed significant changes in some Doppler indices throughout gestation with quantitative differences from singletons, emphasizing the importance of MC twin-specific reference values for clinical application. Further adjustment of MPI for FHR was unnecessary. DV-E is a vascular index indirectly representing fetal diastolic function.

Green Microalgae Strain Improvement for the Production of Sterols and Squalene.

Sterols and squalene are essential biomolecules required for the homeostasis of eukaryotic membrane permeability and fluidity. Both compounds have beneficial effects on human health. As the current sources of sterols and squalene are plant and shark oils, microalgae are suggested as more sustainable sources. Nonetheless, the high costs of production and processing still hinder the commercialization of algal cultivation. Strain improvement for higher product yield and tolerance to harsh environments is an attractive way to reduce costs. Being an intermediate in sterol synthesis, squalene is converted to squalene epoxide by squalene epoxidase. This step is inhibited by terbinafine, a commonly used antifungal drug. In yeasts, some terbinafine-resistant strains overproduced sterols, but similar microalgae strains have not been reported. Mutants that exhibit greater tolerance to terbinafine might accumulate increased sterols and squalene content, along with the ability to tolerate the drug and other stresses, which are beneficial for outdoor cultivation. To explore this possibility, terbinafine-resistant mutants were isolated in the model green microalga Chlamydomonas reinhardtii using UV mutagenesis. Three mutants were identified and all of them exhibited approximately 50 percent overproduction of sterols. Under terbinafine treatment, one of the mutants also accumulated around 50 percent higher levels of squalene. The higher accumulation of pigments and triacylglycerol were also observed. Along with resistance to terbinafine, this mutant also exhibited higher resistance to oxidative stress. Altogether, resistance to terbinafine can be used to screen for strains with increased levels of sterols or squalene in green microalgae without growth compromise.

Morphology, intrafetal vascular pattern, and umbilical artery Doppler indices of acardiac twins.

BACKGROUND: Twin reversed arterial perfusion (TRAP) sequence consists of acardiac twin (A) paradoxically perfused by pump twin (P) through an umbilical artery (UA). We proposed characterization of acardiac twins with intrafetal vascular pattern (IVP), and assessed its correlation with morphology and UA Doppler indices. METHODS: We prospectively evaluated 21 cases of TRAP sequence. Morphology (acardia vs hemicardia) and IVP (simple vs complex) of acardiac twins were characterized with ultrasound and color Doppler. Twins weight ratio (A/P Wt) and UA Doppler indices of acardiac and pump twins including (1) difference of systolic/diastolic ratio (UA ∆S/D), (2) difference of resistance index (UA ∆RI), and (3) ratio of pulsatility index (UA PI A/P) were calculated. RESULTS: The median (min, max) gestational age at diagnosis was 18 (11, 27) weeks. Acardia (n = 14) were associated with simple IVP (n = 16) (P < .05). After exclusion of acardia with complex IVP (n = 1), the A/P Wt, UA ∆S/D, UA ∆RI, and UA PI A/P of acardia with simple IVP (n = 13), hemicardia with simple IVP (n = 3), and hemicardia with complex IVP (n = 4) were not significantly different (P > .05). CONCLUSIONS: Most of acardiac twins were acardia with simple IVP. Morphology and IVP of acardiac twins were not associated with UA Doppler indices.

Simulation-based fetal shunting training.

OBJECTIVES: To develop a simulation model and assess the learning curve of fetal shunting. METHODS: Three staff and three trainees performed fetal shunting on a model using the fetal bladder stent. The model was evaluated according to various sources of validity evidence. The number of procedures to reach competency was determined by the learning curve-cumulative summation (LC-CUSUM) and CUSUM analysis. The learning and control phases were defined as the periods before and after passing the level of competency, respectively. RESULTS: The model was validated to be constructive in the educational process. A total of 600 procedures were carried out with an overall success rate of 94.2% and no significant difference between staff and trainees. The average number of procedures to reach competency was 47. Total procedural time decreased after passing the level of competency. Although the trainees required a longer procedural time in the learning phase than the staff did, there was no significant between-group difference in the control phase. CONCLUSIONS: Using this model, the estimated number of procedures to achieve competency was 47, as substantiated by the increased procedural success and reduced procedural time in the control phase. Training on this simulation model may improve technical performance.

Advanced ultrasound for prenatal interventions.

Ultrasound is an integral part of prenatal interventions. Doppler studies and 3-dimensional ultrasound (3DUS) are frequently used to determine whether fetal surgery is required. The operator's experience remains crucial for reducing procedure-related morbidity. Real-time 3DUS (or 4DUS) can simultaneously display the needle tip in three orthogonal planes, providing reassurance that no fetal parts are in the path. In experienced hands, 4DUS guidance may not be more effective than B-mode, but its value for less-experienced operators remains to be determined. Recent developments in needle, shunt, and video endoscopic technologies may compliment the use of image-guided in utero procedures. Future developments of higher-dimensional transducers and image software may improve the utility of ultrasound for invasive obstetric interventions.