Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “TRIPLETS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed2005

Triplet photophysics of gold(III) porphyrins.

Gold porphyrins are often used as electron-accepting chromophores in donor-acceptor complexes for the study of photoinduced electron transfer, and they can also be involved in triplet-triplet energy-transfer interactions with other chromophores. Since the lowest excited singlet state is very short-lived (240 fs), the triplet state is usually the starting point for the transfer reactions, and it is therefore crucial to understand its photophysics. The triplet state of various gold porphyrins has been reported to have a lifetime of around 1.5 ns at room temperature and to have a biexponential decay both in emission and in transient absorption with decay times of around 10 and 100 micros at 80 K. In this paper, the triplet photophysics of two gold porphyrins (Au(III) 5,15-bis(3,5-di-tert-butylphenyl)-2,8,12,18-tetraethyl-3,7,13,17-tetramethylporphyrin and Au(III) 5,10,15,20-tetra(3,5-di-tert-butylphenyl)porphyrin) are studied by steady-state and time-resolved absorption and emission spectroscopy over a wide temperature range (4-300 K). The study reveals the existence of a dark state with an approximate lifetime of 50 ns, which was not previously observed. This state acts as an intermediate between the short-lived singlet and the triplet state manifold. In addition, we present DFT calculations, in which the core electrons of the central metal were replaced by a pseudopotential to account for the relativistic effects, which suggest that the lowest excited singlet state is an optically forbidden ligand-to-metal charge-transfer (LMCT) state. This LMCT state is an obvious candidate for the experimentally observed dark state, and it is shown to dictate the photophysical properties of gold porphyrins by acting as a gate for triplet state formation versus direct return to the ground state.

Light↗
PubMed2006

Conversion of intramolecular singlet electron transfer at room temperature into triplet energy transfer at 77 K: photoisomerization in norbornadiene- and carbazole-labeled poly(aryl ether) dendrimers.

A series of Fréchet-type poly(aryl ether) dendrimers (CZ-Gn-NBD, n = 1-3) with carbazole (CZ) chromophores and a norbornadiene (NBD) group attached to the periphery and the core, respectively, were synthesized, and their photophysical and photochemical properties were investigated. Selective excitation of the carbazole units in CZ-Gn-NBD resulted in a singlet electron transfer from CZ to NBD at room temperature, and an intersystem crossing followed a triplet-triplet energy transfer from CZ to NBD in glassy 2-methyltetrahydrofuran at 77 K. Both singlet electron transfer and triplet energy transfer processes lead to the isomerization of the norbornadiene group into the quadricyclane (CZ-Gn-QC). The efficiencies and the rate constants for singlet electron transfer are approximately 88, 80, and 74% and 1.8 x 10(9), 6.1 x 10(8), and 4.0 x 10(8) s(-1) for generations 1-3, respectively. The quantum yields of the intramolecular photosensitized isomerization are measured to be approximately 0.013, 0.012, and 0.011, and the efficiencies of triplet norbornadiene formation via singlet electron transfer are approximately 0.070, 0.065, and 0.059 for generations 1-3, respectively. The light-harvesting ability of CZ-Gn-NBD increases with the generation due to an increase of the number of peripheral chromophores. In glassy 2-methyltetrahydrofuran at 77 K, the triplet-triplet energy transfer proceeds with efficiencies of approximately 0.86, 0.64, and 0.36 and rate constants of 0.96, 0.25, and 0.08 s(-1) for generations 1-3, respectively. The intramolecular singlet electron transfer and triplet energy transfer in CZ-Gn-NBD proceed mainly via a through-space mechanism involving the proximate donor (folding back conformation) and acceptor groups.

Journal Article↗
PubMed2005

Spectroscopy and photophysics of self-organized zinc porphyrin nanolayers. 3. Fluorescence detected magnetic resonance of triplet States.

Fluorescence detected magnetic resonance (FDMR) has been applied to approximately 25-nm-thick porphyrin films, containing ordered domains of zinc tetra-(p-octylphenyl)-porphyrin (ZnTOPP) spin-coated onto quartz slides. Illuminating the films at 1.4 K with 457.9-nm light from a continuous wave Ar(+) laser produces at least two different, Jahn-Teller-distorted, ZnTOPP triplet species, labeled i and ii. Microwave-induced magnetic resonance of i and ii in the absence or presence of an externally applied magnetic field affects the fluorescence intensity of ZnTOPP, thus allowing FDMR. For triplet species i, formed in films spin-coated from toluene solution, the zero-field splitting (ZFS) parameters were determined as |D| = (316.9 +/- 0.1) x 10(-4) cm(-1) and |E| = (32.0 +/- 0.5) x 10(-4) cm(-1). By exposure of the spin-coated films to chloroform vapor at room temperature, triplet i is converted into species ii, with |D| = (295 +/- 3) x 10(-4) cm(-1) and |E| = (121 +/- 3) x 10(-4) cm(-1). For the excited triplet state of ZnTOPP in a toluene glass, ZFS parameters with values of |D| = (295 +/- 1) x 10(-4) cm(-1) and |E| = (91 +/- 1) x 10(-4) cm(-1) are found. From a combined study of the FDMR- and microwave-induced fluorescence spectra, i and ii are identified as unligated and ligated ZnTOPP triplet species, respectively. From the asymmetrically shaped zero-field FDMR signals of i, we conclude that the local crystal field perturbations of the stacked molecules are anisotropic. The FDMR results of the ZnTOPP films are compared with those for a film of zinc tetraphenylporphyrin (ZnTPP), which lacks the octyl substituents, and therefore is nonordered. Upon illumination, the ZnTPP films contain only a single, ligated, triplet species with ZFS parameters very similar to those of ligated ZnTOPP. At approximately 5 K, the lifetime of triplet i is considerably shortened compared to that of ZnTOPP in a glass at the same temperature.

Magnetics↗
PubMed2006

Triplet-state and singlet oxygen formation in fluorene-based alternating copolymers.

Data are reported on the triplet states of a series of fluorene-based A-alt-B type alternating copolymers based on pulse radiolysis-energy transfer and flash photolysis experiments. From the pulse radiolysis experiments, spectra are given for eight copolymers involving phenylene, thiophene, benzothiadiazole, and oligothienylenevinylene groups. Quantum yields for triplet-state formation (PhiT) have been obtained by flash photolysis following laser excitation and in one case by photoacoustic calorimetry. In addition, yields of sensitized formation of singlet oxygen have been determined by time-resolved phosphorescence and are, in general, in excellent agreement with the PhiT values. In all cases, the presence of thiophene units is seen to increase intersystem-crossing quantum yields, probably because of the presence of the heavy sulfur atom. However, with the poly[2,7-(9,9-bis(2'-ethylhexyl)fluorene)-alt-1,4-phenylene] (PFP), thiophene S,S-dioxide (PFTSO2) and benzothiadiazole (F8BT) copolymers, low yields of triplet formation are observed. With three of the copolymers, the energies of the triplet states have been determined. With PFP, the triplet energy is virtually identical to that of poly[2,7-(9,9-bis(2'-ethylhexyl)fluorene)]. In contrast, with fluorene-thiophene copolymers PFaT and PF3T, the triplet energies are closer to those of thiophene oligomers, indicating that there is significant conjugation between fluorene and thiophene units but also that there is a more localized triplet state than with the homopolymers.

Algorithms↗
PubMed2006

Asymmetry in platinum acetylide complexes: confinement of the triplet exciton to the lowest energy ligand.

To determine structure-optical property relationships in asymmetric platinum acetylide complexes, we synthesized the compounds trans-Pt(PBu3)2(C[triple bond]CC6H5)(C[triple bond]C-C6H4-C[triple bond]CC6H5) (PE1-2), trans-Pt(PBu3)2(C[triple bond]CC6H5)(C[triple bond]C-C6H4-C[triple bond]C-C6H4-C[triple bond]CC6H5) (PE1-3) and trans-Pt(PBu3)2(C[triple bond]C-C6H4-C[triple bond]CC6H5)(C[triple bond]C-C6H4-C[triple bond]C-C6H4-C[triple bond]CC6H5) (PE2-3) that have different ligands on either side of the platinum and compared their spectroscopic properties to the symmetrical compounds PE1, PE2 and PE3. We measured ground state absorption, fluorescence, phosphorescence and triplet state absorption spectra and performed density functional theory (DFT) calculations of frontier orbitals, lowest lying singlet states, triplet state geometries and energies. The absorption and emission spectra give evidence the singlet exciton is delocalized across the central platinum atom. The phosphorescence from the asymmetric complexes comes from the largest ligand. Time-dependent (TD) DFT calculations show the S1 state has mostly highest occupied molecular orbital (HOMO) --> lowest unoccupied molecular orbital (LUMO) character, with the LUMO delocalized over the chromophore. In the asymmetric chromophores, the LUMO resides on the larger ligand, suggesting the S1 state has interligand charge transfer character. The triplet state geometries obtained from the DFT calculations show distortion on the lowest energy ligand, whereas the other ligand has the ground state geometry. The calculated trend in the triplet state energies agrees very well with the experimental trend. Calculations of triplet state spin density also show the triplet exciton is confined to one ligand. In the asymmetric complexes the spin density is confined to the largest ligand. The results show Kasha's rule applies to these complexes, where the triplet exciton moves to the lowest energy ligand.

Journal Article↗
PubMed1998

Analysis of strand slippage in DNA polymerase expansions of CAG/CTG triplet repeats associated with neurodegenerative disease.

Lengthy expansions of trinucleotide repeats are found in DNA of patients suffering severe neurodegenerative age-related diseases. Using a synthetic self-priming DNA, containing CAG and CTG repeats implicated in Huntington's disease and several other neurological disorders, we measure the equilibrium distribution of hairpin folding and generate triplet repeat expansions by polymerase-catalyzed extensions of the hairpin folds. Expansions occur by slippage in steps of two CAG triplets when the self-priming sequence (CTG)16(CAG)4 is extended with proofreading-defective Klenow fragment (KF exo-) from Escherichia coli DNA polymerase I. Slippage by two triplets is 20 times more frequent than by one triplet, in accordance with our finding that hairpin loops with even numbers of triplets are 1-2 kcal/mol more stable than their odd-numbered counterparts. By measuring triplet repeat expansions as they evolve over time, individual rate constants for expansion from 4 to 18 CAG repeats are obtained. An empirical expression is derived from the data, enabling the prediction of slippage rates from the ratio of hairpin CTG/CTG interactions to CAG/CTG interactions. Slippage is initiated internally in the hairpin folds in preference to melting inward from the 3' terminus. The same triplet expansions are obtained using proofreading-proficient KF exo+, provided 10-100-fold higher dNTP concentrations are present to counteract the effect of 3'-exonucleolytic proofreading.

Base Sequence↗
PubMed2003

Type I collagen triplet duplication mutation in lethal osteogenesis imperfecta shifts register of alpha chains throughout the helix and disrupts incorporation of mutant helices into fibrils and extracellular matrix.

The majority of collagen mutations causing osteogenesis imperfecta (OI) are glycine substitutions that disrupt formation of the triple helix. A rare type of collagen mutation consists of a duplication or deletion of one or two Gly-X-Y triplets. These mutations shift the register of collagen chains with respect to each other in the helix but do not interrupt the triplet sequence, yet they have severe clinical consequences. We investigated the effect of shifting the register of the collagen helix by a single Gly-X-Y triplet on collagen assembly, stability, and incorporation into fibrils and matrix. These studies utilized a triplet duplication in COL1A1 exon 44 that occurred in the cDNA and gDNA of two siblings with lethal OI. The normal allele encodes three identical Gly-Ala-Hyp triplets at aa 868-876, whereas the mutant allele encodes four. The register shift delays helix formation, causing overmodification. Differential scanning calorimetry yielded a decrease in T(m) of 2 degrees C for helices with one mutant chain and a 6 degrees C decrease in helices with two mutant chains. An in vitro binary co-processing assay of N-proteinase cleavage demonstrated that procollagen with the triplet duplication has slower N-propeptide cleavage than in normal controls or procollagen with proalpha1(I) G832S, G898S, or G997S substitutions, showing that the register shift persists through the entire helix. The register shift disrupts incorporation of mutant collagen into fibrils and matrix. Proband fibrils formed inefficiently in vitro and contained only normal helices and helices with a single mutant chain. Helices with two mutant chains and a significant portion of helices with one mutant chain did not form fibrils. In matrix deposited by proband fibroblasts, mutant chains were abundant in the immaturely cross-linked fraction but constituted a minor fraction of maturely cross-linked chains. The profound effects of shifting the collagen triplet register on chain interactions in the helix and on fibril formation correlate with the severe clinical consequences.

Adult↗
PubMed2005

New insights into DNA triplexes: residual twist and radial difference as measures of base triplet non-isomorphism and their implication to sequence-dependent non-uniform DNA triplex.

DNA triplexes are formed by both isomorphic (structurally alike) and non-isomorphic (structurally dissimilar) base triplets. It is espoused here that (i) the base triplet non-isomorphism may be articulated in structural terms by a residual twist (Delta(t) degrees), the angle formed by line joining the C1'...C1' atoms of the adjacent Hoogsteen or reverse Hoogsteen (RH) base pairs and the difference in base triplet radius (Delta(r) A), and (ii) their influence on DNA triplex is largely mechanistic, leading to the prediction of a high (t + Delta(t))degrees and low (t - Deltat)degrees twist at the successive steps of Hoogsteen or RH duplex of a parallel or antiparallel triplex. Efficacy of this concept is corroborated by molecular dynamics (MD) simulation of an antiparallel DNA triplex comprising alternating non-isomorphic G*GC and T*AT triplets. Conformational changes necessitated by base triplet non-isomorphism are found to induce an alternating (i) high anti and anti glycosyl and (ii) BII and an unusual BIII conformation resulting in a zigzag backbone for the RH strand. Thus, base triplet non-isomorphism causes DNA triplexes into exhibiting sequence-dependent non-uniform conformation. Such structural variations may be relevant in deciphering the specificity of interaction with DNA triplex binding proteins. Seemingly then, residual twist (Delta(t) degrees) and radial difference (Deltar A) suffice as indices to define and monitor the effect of base triplet non-isomorphism in nucleic acid triplexes.

Base Pairing↗
PubMed2005

Hospitalisation for bed rest for women with a triplet pregnancy: an abandoned randomised controlled trial and meta-analysis.

BACKGROUND: This abandoned randomised controlled trial assessed the effects of hospitalisation from 24 to 30 weeks gestation for women with a triplet pregnancy on the risk of preterm birth. METHODS: Women with a triplet pregnancy and no other condition necessitating hospital admission were approached for participation in the study, and randomised to either antenatal hospitalisation (hospitalised group), or to routine antenatal care (control group). The randomisation schedule used variable blocks with stratification by parity, and a researcher not involved with clinical care contacted by telephone to determine treatment allocation by opening the next in a series of consecutively numbered, opaque, sealed envelopes. Primary study outcomes were preterm birth (defined as birth less than 37 weeks gestation) and very preterm birth (defined as birth less than 34 weeks gestation), and the development of maternal pregnancy induced hypertension. The trial was ceased prior to achieving the calculated sample size due to difficulties in recruitment. The results of this randomised controlled trial were then combined with the results of another comparing bed rest in women with a triplet pregnancy. RESULTS: Seven women with a triplet pregnancy were recruited to the trial, with three randomised to the hospitalisation group, and four to the control group. There were no statistically significant differences between the two groups for the primary outcomes birth before 37 weeks (3/3 hospitalisation group versus 4/4 control group; relative risk (RR) not estimable), birth before 34 weeks (3/3 hospitalisation group versus 2/4 control group; RR 2.00 95% Confidence Intervals (CI) 0.75-5.33) and pregnancy induced hypertension (1/3 hospitalisation group versus 1/4 control group; RR 1.33 95%CI 0.13-13.74).When the results of this trial were incorporated into a meta-analysis with the previous randomised controlled trial assessing hospitalisation and bed rest for women with a triplet pregnancy, (total sample size 26 women and 78 infants), there were no statistically significant differences identified between the two groups. CONCLUSION: The results of this trial and meta-analysis suggest no benefit of routine hospitalisation and bed rest for women with a triplet pregnancy to reduce the risk of preterm birth. The adoption or continuation of a policy of routine hospitalisation and bed rest for women with an uncomplicated triplet pregnancy cannot be recommended.

Journal Article↗
PubMed2006

Alpha-internexin is structurally and functionally associated with the neurofilament triplet proteins in the mature CNS.

Alpha-internexin, a neuronal intermediate filament protein implicated in neurodegenerative disease, coexists with the neurofilament (NF) triplet proteins (NF-L, NF-M, and NF-H) but has an unknown function. The earlier peak expression of alpha-internexin than the triplet during brain development and its ability to form homopolymers, unlike the triplet, which are obligate heteropolymers, have supported a widely held view that alpha-internexin and neurofilament triplet form separate filament systems. Here, we demonstrate, however, that despite a postnatal decline in expression, alpha-internexin is as abundant as the triplet in the adult CNS and exists in a relatively fixed stoichiometry with these subunits. Alpha-internexin exhibits transport and turnover rates identical to those of triplet proteins in optic axons and colocalizes with NF-M on single neurofilaments by immunogold electron microscopy. Alpha-internexin also coassembles with all three neurofilament proteins into a single network of filaments in quadruple-transfected SW13vim(-) cells. Genetically deleting NF-M alone or together with NF-H in mice dramatically reduces alpha-internexin transport and content in axons throughout the CNS. Moreover, deleting alpha-internexin potentiates the effects of NF-M deletion on NF-H and NF-L transport. Finally, overexpressing a NF-H-LacZ fusion protein in mice induces alpha-internexin and neurofilament triplet to aggregate in neuronal perikarya and greatly reduces their transport and content selectively in axons. Our data show that alpha-internexin and the neurofilament proteins are functionally interdependent. The results strongly support the view that alpha-internexin is a fourth subunit of neurofilaments in the adult CNS, providing a basis for its close relationship with neurofilaments in CNS diseases associated with neurofilament accumulation.

Animals↗
PubMed1991

Differential changes in expression of the neurofilament triplet protein-immunoreactivity in Purkinje cells of the cerebellum during the postnatal development of rats.

By means of peroxidase-anti-peroxidase (PAP) immunohistochemistry with both the neurofilament (NF) triplet (small: 68 K, medium: 150 K, high: 200 K) antisera and the antiserum against spot 35-calbindin, developmental changes in expression of the immunoreactivity for the NF triplet proteins in different domains of the Purkinje cells was examined in the cerebella of postnatal rats. From birth till the postnatal day 6 (P6) the somata and dendrites exhibited moderately positive immunoreaction for small and medium NF subunits. In contrast, the incubation for the high NF subunit resulted in a negative immunoreaction for the somata and dendrites of the Purkinje cells at those stages. On P8 and P10 they were weakly immunoreactive for all NF triplet. Thereafter the intensity of their immunoreaction decreased progressively and the Purkinje cell somata and dendrites were immunonegative for all NF triplet proteins on P21, when the Purkinje cell attained an adult appearance in morphology. On the other hand, the Purkinje cell axons, which can be identified selectively by the positive immunoreaction for the spot 35-calbindin throughout the course of the postnatal development, exhibited positive immunoreactivity for all the NF triplet on the 9th, 21th and 50th postnatal days in the cerebellar white matter. The development of the slow axoplasmic transport and the posttranslational modification of the NF triplet proteins are discussed as possible mechanisms underlying the differential expression of the immunoreactivity for the NF triplet proteins in different domains of the Purkinje cells during postnatal development.

Animals↗
PubMedDate not supplied

[Quantitative comparison of ribosome binding sites of twelve nucleotide sequences from Escherichia coli (RNA- and DNA phages) based on triplet patterns (author's transl)].

The molecular structure of ribosome binding sites of ten phage genes and two messengers of Escherichia coli were compared concerning the signation parts which are presumably used by ribosomes for recognition and binding. With a simple calculation based on triplet patterns sofar unknown agreements between all of these sequences were found. In several cases it was shown that agreements between old sequences are easier recognizable if the purine- and pyrimidine bases are put into the triplets instead of the four A, G, C, and U (T) bases. In such cases "homologous" parts of sequences were recognized with more distinctness. This is true in our case for the double triplet (hexaplet) py-pu-pu-pu-pu-(pu) and the binding site triplet py-pu-pu, which are preceding the initiator. These triplets are in specific positions in all twelve sequences which were compared. The different course of the quaternary and the binary conformity curves (diagram 1) may show for the investigated area that the RNA phage gene-part is organized according to the well known quaternary triplet code. On the contrary the phage phi-gene-part seems to be organized according to a more simple, binary triplet sequence of purine and pyrimidine bases. The binary sequence seems to be the more original, the quaternary the derived one.

Base Sequence↗
PubMed1998

The photobiological differences of gilvocarcins V and M are not related to their transient intermediates and triplet yields.

The transient absorption spectra of the intermediates produced by the 355 nm laser excitation of gilvocarcin derivatives have been investigated in various solvents. The spectra consist of a triplet-triplet absorption in the visible region and a residual absorption observed between 340 and 700 nm due to a long-lived species, assigned to the radical cation. A broad-fast decaying band with a maximum at around 700 nm attributed to the solvated electron is also seen in solutions containing a low DMSO/water volume ratio and at 266 nm irradiation of a 50% methanol/water solvent mixture. The molar absorption coefficient of the triplet state of gilvocarcin V (GV) and gilvocarcin M (GM), determined by the energy transfer method, is independent of the solvent properties and has a value of 3.0 x 10(4)/Mcm. The triplet decay rate constants for both drugs are between 1 and 5 x 10(4)/s. A similar initial yield and triplet decay rate constant of GV were observed in the presence of 3.4 mM thymine. Thus, a quenching rate constant of the GV's triplet state by thymine is estimated to be lower than 10(6)/Ms. The triplet quantum yields of both antibiotics determined by using the comparative method are higher in dimethylsulfoxide (DMSO) (0.18) than are those corresponding to 25% DMSO/water (0.06). The decrease in phi T in the presence of water could be attributed to an enhanced internal conversion rate constant from the S1 state or to an increase in the photoionization yield. The similarity of the transient intermediates and their yields for GV and GM suggest that their photobiological differences are due to other factors such as DNA binding constants, preferential localization of the drugs in the cell or the enhanced reactivity of the vinyl group toward cellular components.

Aminoglycosides↗
PubMed2004

Targeted first-trimester prenatal diagnosis before fetal reduction in triplet gestations and subsequent outcome.

OBJECTIVE: To assess the feasibility of targeted first-trimester ultrasound evaluation in triplet gestations and to report the outcome in reduced and expectantly managed triplets. METHODS: This was a retrospective analysis of 127 triplets at 11-14 weeks with targeted ultrasound examination including nuchal translucency (NT) screening. RESULTS: One or more abnormal findings were observed in 33 of 381 fetuses (8.7%), including increased NT (n = 18), malformations (n = 4), aneuploidy (n = 3), relative intrauterine growth restriction (n = 2) or spontaneous demise (n = 13). Of 63 patients (49%) who chose reduction, selective termination due to abnormal findings was performed in 13 fetuses. The rates of complete abortion <24 weeks were 9.8% and 3.2% for those with expectant management and fetal reduction, respectively. Expectantly managed triplets delivered significantly earlier (31.1 +/- 3.8 vs. 35.6 +/- 3.3 weeks) (P < 0.01) with a lower mean birth weight (1483 +/- 552 g vs. 2305 +/- 557 g) (P < 0.01) and a lower number of liveborn fetuses (85.6% vs. 97.4%) (P < 0.01) than those reduced. CONCLUSION: Targeted first-trimester ultrasound is feasible and reliable in triplet gestations and should be an integral part of the counseling process. It results in more accurate selection for those who consider fetal reduction. Our data further support fetal reduction as a valuable strategy to improve perinatal outcome in triplet pregnancies.

Adult↗
PubMed1994

Perinatal outcome of triplet pregnancies following assisted reproduction.

PURPOSE: This collaborative work was undertaken to assess perinatal outcome of in vivo conceived triplets to those following in vitro fertilization and assisted reproductive technologies (ART). METHODS: 151 triplets were examined; 56 delivered following ART, 55 following ovulation induction by gonadotropins (GN), 27 following clomiphene citrate (CC), and 13 conceived spontaneously. RESULTS: Mean gestational length of triplets following ART (33.2 wks) was not different from those conceived following GN (33.4 wks) or CC (34.2 wks), but was significantly shorter compared to triplets following spontaneous conception (35.3 wks). Mean fetal birthweight following ART (1743 g) did not differ significantly from that following GN (1683 g) or CC (1863 g) but was significantly lower compared to those delivered after spontaneous conception (1963 g). Although no difference was found in the incidence of low birthweight infants between the groups studied, the incidence of very low birthweight newborns (<1500 g) following ART or GN was significantly higher than following spontaneous conceptions (30.6%, 30.3% vs 10.3%). Differences in perinatal mortality were not significantly different between the groups examined (77.9, 60.6, 111.0, 25.6/1000 for ART, GN, CC, and spontaneous conceptions respectively). CONCLUSION: In conclusion, a similar perinatal outcome was shown for triplets conceived following ART and those following ovulation induction by GN, suggesting that the in vitro conditions as such were not the main contributing factor influencing the clinical outcome but rather the GN treatment. Triplets conceived spontaneously have a better outcome compared to those following ovulation induction or ART in terms of gestational length and birthweight.

Birth Weight↗
PubMed2002

Triplet placentas: reference values for weights.

The occurrence of twins, triplets, and other multiple births increased significantly between 1970 and 2000 in the United States and other industrialized countries. The number of triplet placentas submitted for examination as pathologic specimens has also markedly increased, but no reference values are published for triplet weights. We examined 196 normal triplet placentas. Specimens with associated conditions known to affect the weights of the placentas were excluded. The gestational ages ranged between 20 and 38 weeks. Mean weights for different gestational ages are summarized as follows: 253 g for 20 weeks, 319 g for 22 weeks, 406 g for 24 weeks, 509 g for 26 weeks, 621 g for 28 weeks, 738 g for 30 weeks, 855 g for 32 weeks, 965 g for 34 weeks, 1,065 g for 36 weeks, and 1,147 g for 38 weeks. Weight gain of triplet placentas appears to parallel that of twin placentas. The mean values of placental weights for triplets at each gestational age are less than triple those of singleton weights for the same duration of gestation. The placental weights in multiple gestations do not increase proportionately with the number of fetuses.

Female↗
PubMed1996

Prenatal determination of chorionicity in triplet pregnancy by ultrasonographic examination of the ipsilon zone.

OBJECTIVE: To determine chorionicity in triplet pregnancies by ultrasonographic assessment of the ipsilon zone, the junction of the three interfetal membranes. METHODS: The thickness of the component membranes in the ipsilon zone was studied to determine chorionicity in 28 triplet pregnancies, by retrospective examination of the ultrasonographic images taken at 9-24 weeks' gestation, and in 20 consecutive triplet pregnancies followed prospectively by targeted ultrasonography at 8-21 weeks' gestation. Prenatal ultrasonographic findings were compared with those obtained from the records of the infertility centers or referring hospitals (the number of gestational sacs and live embryos in each sac seen by transvaginal scanning at 6-7 weeks' gestation). RESULTS: Of the 28 triplet pregnancies with appropriate images demonstrating the ipsilon zone, 22 were classified as trichorionic, five dichorionic, and one monochorionic. This classification was correct in all but one trichorionic pregnancy, which was misclassified as dichorionic. In the prospective subset (n = 20) there were 16 trichorionic and four dichorionic triplet pregnancies. The ipsilon zone was not present in one case in which the interfetal membrane did not intersect. In the remaining 19 pregnancies, there was a complete correlation between the findings at the ipsilon zone and transvaginal ultrasonography at 6-7 weeks. CONCLUSION: Ultrasonographic assessment of the ipsilon zone is useful for predicting chorionicity in triplet pregnancies.

Chorion↗
PubMed2005

Prophylactic cerclage in the management of triplet pregnancies.

OBJECTIVE: The purpose of this study was to determine if prophylactic cerclage improves pregnancy outcome in women with triplet pregnancies without a history of cervical insufficiency. STUDY DESIGN: Triplet pregnancies with > or = 1 day of outpatient surveillance beginning before 32 weeks' gestation were identified from a database of women in the US who received outpatient preterm labor surveillance services between January 1990 and May 2004. Triplet pregnancies managed with prophylactic cerclage were compared with triplet pregnancies in which cerclage was not placed. Patients with a diagnosis of cervical insufficiency in a previous or in the index pregnancy were excluded from analysis. The primary outcome was incidence of preterm birth before 32 weeks. Groups were compared using Fisher exact test, and Student t test with 2-sided P values < .05 considered statistically significant. RESULTS: Three thousand two hundred seventy-eight triplet pregnancies met criteria for inclusion, of which 248 women (7.6%) received prophylactic cerclage. No significant differences were seen in mean gestational age at delivery, incidence of preterm birth before 32 weeks, birth weight, or neonatal days in the hospital. This study had 80% power to detect a 30% reduction in the primary outcome. CONCLUSION: Prophylactic cerclage did not result in improved pregnancy or neonatal outcomes in triplet pregnancies without a history of cervical insufficiency.

Adult↗