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PubMed1998

Triplet energy transfer in bacterial photosynthetic reaction centres.

[3-vinyl]-132-OH-bacteriochlorophyll a has been selectively exchanged against native bacteriochlorophyll a in the monomer binding sites at the A- and B-branch of the photosynthetic reaction centre from Rhodobacter sphaeroides. Transient absorption difference measurements were performed on these samples over a temperature range from 4.2 to 300 K with 20 ns time resolution. Specifically the decay of the primary donor triplet state, 3P870, as well as the rise and decay rates of the carotenoid triplet state, 3Car (spheroidene), were measured. The observed rates revealed a thermally activated carotenoid triplet formation corresponding to the decay of the primary donor triplet state. The activation energies for the triplet energy transfer process were 100(+/-10) cm-1 for reaction centers from wild-type Rhodobacter sphaeroides 2.4.1, with and without exchange of the monomeric bacteriochlorophyll on the electron transfer-active branch, BA. For reaction centers from Rhodobacter sphaeroides R26.1 with both monomers exchanged against [3-vinyl]-132-OH-bacteriochlorophyll a, and subsequent spheroidene reconstitution the activation energy was 460(+/-20) cm-1. These activation energies correspond to the energy difference between the triplet states of the accessory BChl monomer, BB, and the primary donor when native BChl a or [3-vinyl]-132-OH-BChl a is present in the BB binding site. In all samples the 3Car formation rates were bi-phasic over a large temperature range. A fast temperature-independent rate was observed on the wavelength of the carotenoid triplet-triplet absorption which dominated at very low temperatures. Additionally, a slower temperature-independent 3Car formation rate was observed at low temperatures which could be explained with the assumption of heterogeneity in the energy barrier (3BB) and/or the primary donor triplet state (3P870). A tunneling mechanism as proposed earlier by Kolaczkowski (PhD thesis, Brown University, 1989) is not only unnecessary but also incompatible with the available experimental data.

Journal Article↗
PubMed1992

Spectroscopic characterization of triplet forming states in photosystem II.

Fluorescence and electron paramagnetic resonance (EPR) measurements have been applied to characterize chlorophyll triplet formation in the reaction center of photosystem II (PSII). A highly triplet forming state was generated in PSII membranes by chemical double reduction of the primary electron acceptor QA. In triplet forming PSII centers, the steady-state yield of chlorophyll fluorescence decreased to about 70% of the maximal fluorescence yield observed in closed PSII centers in which QA is singly reduced. The results are well interpreted in the framework of a model where the charge state of QA electrostatically controls the yield of primary charge separation [Schatz, G. H., Brock, H., & Holzwarth, A. R. (1988) Biophys. J. 54, 397-405]. Thus, high triplet yield and decreased, although still quite high, fluorescence indicate a charge-neutralized state of PSII in which QA is singly or doubly reduced and protonated or absent. The EPR signal of the triplet primary chlorophyll donor, 3P680, is suppressed by illumination at 77 K concomitant with the formation of a cationic radical (g = 2.0025-2.0027, and 0.92 mT wide) that is stable in the dark. This is attributed to the oxidation of an accessory chlorophyll (Chl) in the vicinity of P680. Electrostatic repulsion between Chl+ and P680+ is likely to prevent primary charge separation, and in turn triplet formation, providing a further example of electrostatic control of primary charge separation. The triplet P680 EPR signal is also suppressed in the presence of oxygen. This effect, which is almost completely reversible by removing the oxygen, is attributed to the interaction of triplet P680 with triplet O2.

Benzyl Viologen↗
PubMed2002

Chlorophyll triplet states associated with photosystem II of thylakoids.

The analysis of FDMR thylakoid spectra, determined at multiple emission wavelengths, by a global decomposition technique, has revealed the presence of three previously undescribed triplet populations at emission wavelengths characteristic of Photosystem II chlorophyll/protein complexes. Their zero-field splitting parameters have been determined in order to compare them with the well-studied PSII recombination triplet state. None of these triplets have the zero-field splitting parameters characteristic of the recombination triplet and are therefore probably not generated directly in the reaction center. On the basis of their microwave-induced emission spectra, it is suggested that two are probably generated in the core complex(es) while the third may be generated in the external antenna. These triplets are formed under nonreducing redox conditions, when the recombination triplet is undetectable. It is suggested that they may be involved in the photoinhibitory damage of Photosystem II. The triplet-minus-singlet spectrum associated with the recombination triplet state has been determined for thylakoids after reduction of the secondary acceptors. Its main peak is at 685 nm, slightly red shifted with respect to earlier reports, with a weak signal, of opposite sign at approximately 675 nm. The 685 nm peak indicates that at cryogenic temperatures, the triplet is located on the long-wavelength chlorophyll state present in the reaction center complex of Photosystem II (D1.D2.Cytb(559) complex). From the absence of a clear structure in the 680 nm absorption region, this long-wavelength absorbing state does not appear to be strongly coupled to P(680), though it must be associated with one of the "inner core" pigments recently identified in the photosystem II crystallographic structure [Zouni et al. (2001) Nature 408, 739-743].

Chlorophyll↗
PubMed2005

Quenching of chlorophyll triplet states by carotenoids in reconstituted Lhca4 subunit of peripheral light-harvesting complex of photosystem I.

In this study, triplet quenching, the major photoprotection mechanism in antenna proteins, has been studied in the light-harvesting complex of photosystem I (LHC-I). The ability of carotenoids bound to LHC-I subunit Lhca4, which is characterized by the presence of the red-most absorption components at wavelength >700 nm, to protect the system through quenching of the chlorophyll triplet states, has been probed, by analyzing the induction of carotenoid triplet formation. We have investigated this process at low temperature, when the funneling of the excitation toward the low-lying excited states of the Chls is stronger, by means of optically detected magnetic resonance (ODMR), which is well-suited for investigation of triplet states in photosynthetic systems. The high selectivity and sensitivity of the technique has made it possible to point out the presence of specific interactions between carotenoids forming the triplet states and specific chlorophylls characterized by red-shifted absorption, by detection of the microwave-induced Triplet minus Singlet (T-S) spectra. The effect of the red forms on the efficiency of triplet quenching was specifically probed by using the Asn47His mutant, in which the red forms have been selectively abolished (Morosinotto, T., Breton, J., Bassi, R., and Croce, R. (2003) J. Biol. Chem. 278, 49223-49229). Lack of the red forms yields into a reduced efficiency of the triplet quenching in LHC-I thus suggesting that the "red Chls" play a role in enhancing triplet quenching in LHC-I and, possibly, in the whole photosystem I.

Amino Acid Substitution↗
PubMed1998

Triplet properties and interactions of the primary electron donor and antenna chromophores in membranes of Heliobacterium chlorum, studied with ADMR spectroscopy.

The triplet states of antenna and reaction center bacteriochlorophyll (BChl) g in membranes of Heliobacterium chlorum were studied by optically detected magnetic resonance in zero magnetic field, using absorbance detection. A variety of triplet states was detected, which were all localized on single BChl g chromophores as concluded from a comparison with the triplet state of monomeric BChl g in organic solvents. With the aid of the microwave-induced absorbance difference spectra, we assign a triplet state with zero-field splitting parameters |D| = 727.5 and |E| = 254. 5 MHz to that of the primary donor. The low |E| value indicates that the BChls of the primary donor are monoligated. The intensities of the zero-field transitions were strongly dependent on the redox state of the secondary electron acceptors. A triplet state with |D| = 690-705 MHz and |E| =230 MHz, present under all redox conditions, is associated with antenna BChl g absorbing at 814 nm. Its triplet yield was independent of the redox conditions; we conclude therefore that the antenna chromophores absorbing at 814 nm are not connected with the reaction center at cryogenic temperatures (1.2 K). In addition, relatively strong signals were detected belonging to triplet states with |D| and |E| of 663-680 and 220-227 MHz, respectively, whose amplitudes were dependent on the redox conditions. Triplet states with these zero-field splitting parameters are located on antenna chromophores absorbing between 798-814 nm; their zero-field transitions and absorbance difference spectra indicate a considerable heterogeneity. The concentration of triplet states of antenna chromophores absorbing around 800 nm decreased markedly upon prolonged excitation at 1.2 K. This phenomenon is attributed to quenching of excitations on antenna pigments by stable charge separation in the closely connected reaction center, possibly involving a low-quantum yield menaquinone electron acceptor.

Bacteria↗
PubMed2004

The photoinduced triplet of flavins and its protonation states.

The photogenerated triplet states of riboflavin and flavin mononucleotide (FMN) have been examined by time-resolved electron paramagnetic resonance (EPR) spectroscopy at low temperature (T = 80 K). Because of the high time resolution of the utilized EPR instrumentation, the triplets are for the first time observed in the nonequilibrated electron-spin polarized state and not in their equilibrated forms with the population of the triplet sublevels governed by Boltzmann distribution. The electron-spin polarization pattern directly reflects the anisotropy of the intersystem crossing from the excited singlet-state precursor. Spectral analysis of the resulting enhanced absorptive and emissive EPR signals yields the zero-field splitting parameters, |D| and |E|, and the zero-field populations of the triplet at high accuracy. These parameters are sensitive probes for the protonation state of the flavin's isoalloxazine ring, as becomes evident by a comparison of the spectra recorded at different pH values of the solvent. The three protonation states of the flavins can furthermore be distinguished by the kinetics of the transient EPR signals, which are dominated by spin-lattice relaxation. The fastest decays are observed for the protonated FMN and riboflavin triplets, followed by the deprotonated flavin triplets. Slow decays are measured for the triplet states of neutral FMN and riboflavin. Because proton transfer is found to be slow on the time scale of spin-polarized triplet detection by transient EPR, the pH-dependent spin-relaxation and zero-field splitting parameters offer a novel approach to probe the protonation state of flavins in their singlet ground state through the characterization of their triplet-state properties.

Electron Spin Resonance Spectroscopy↗
PubMed2003

Photolysis of alpha-azidoacetophenones: direct detection of triplet alkyl nitrenes in solution.

We report the first detection of triplet alkyl nitrenes in fluid solution by laser flash photolysis of alpha-azido acetophenone derivatives, 1. Alphazides 1 contain an intramolecular triplet sensitizer, which ensures formation of the triplet alkyl nitrene by bypassing the singlet nitrene intermediate. At room temperature, azides 1 cleave to form benzoyl and methyl azide radicals in competition with triplet energy transfer to form triplet alkyl nitrene. The major photoproduct 3 arises from interception of the triplet alkyl nitrene with benzoyl radicals. The triplet alkyl nitrene intermediates are also trapped with molecular oxygen to yield the corresponding 2-nitrophenylethanone. Laser flash photolysis of 1 reveals that the triplet alkyl nitrenes have absorption around 300 nm. The triplet alkyl nitrenes were further characterized by obtaining their UV and IR spectra in argon matrices. (13)C and (15)N isotope labeling studies allowed us to characterize the C-N stretch of the nitrene intermediate at 1201 cm(-)(1).

Journal Article↗
PubMed2004

Time-resolved resonance Raman study of the triplet states of p-hydroxyacetophenone and the p-hydroxyphenacyl diethyl phosphate phototrigger compound.

Pico- and nanosecond time-resolved resonance Raman (TR3) spectroscopy have been utilized to study the dynamics and structure of p-hydroxyacetophenone (HA) and the p-hydroxyphenacyl-caged phototrigger compound p-hydroxyphenacyl diethyl phosphate (HPDP) in acetonitrile solution. Transient intermediates were detected and attributed to the triplet states of HA and HPDP. Nanosecond-TR3 measurements were done for two isotopically substituted HA molecules to help better assign the triplet state carbonyl C=O stretching and the ring related vibrational modes. The dynamics of formation and the spectral characteristics for the triplet states were found to be similar for the HA and HPDP. The temporal evolution at very early picosecond time scale indicates there is rapid intersystem crossing (ISC) conversion and subsequent relaxation of the excess energy of the initially produced energetic triplet state. B3LYP/6-311G** density functional theory (DFT) calculations were done to determine the structures and vibrational frequencies for both the triplet and ground states of HA and HPDP. The calculated spectra reproduce the experimental spectra and the observed isotopic shifts reasonably well and were used to make tentative assignments to all the experimentally observed features. The triplet states were found to have extensive conjugated pipi* nature with a single-bond-like carbonyl CO bond. We briefly compare the triplet structure and formation dynamics of HA and HPDP as well as the conformational changes upon going from the ground state to the triplet state. We discuss our present results in relation to the initial pathway for the p-hydroxyphenacyl photodeprotection process. We also compare and discuss the properties of the HA pipi* triplet state relative to the published results of other aromatic carbonyl compounds.

Journal Article↗
PubMed2002

Photochemical properties of the triplet pi,pi* state, anion and ketyl radicals of 5,12-naphthacenequinone in solution studied by laser flash photolysis: electron transfer and phenolic H-atom transfer.

Photochemical properties of the lowest triplet pi,pi* state of 5,12-naphthacenequinone (5,12-NQ) have been investigated in solution by means of nanosecond laser flash photolysis at 295 K. The transient absorption spectrum of triplet 5,12-NQ was measured in CCl4 and the molar absorption coefficient was determined. In CCl4, triplet 5,12-NQ is shown to be quenched by the ground-state 5,12-NQ. In acetonitrile, triplet 5,12-NQ is quenched by 1,2,4,5-tetramethoxybenzene (TMB) via electron transfer to produce the TMB cation and 5,12-NQ anion radicals. The absorption spectrum and the molar absorption coefficient of the 5,12-NQ anion radical were determined based on those of the TMB cation radical. Although triplet 5,12-NQ does not abstract H-atom of ethanol or cyclohexane, H-atom transfer occurs from phenol and p-phenylphenol to triplet 5,12-NQ, producing the 5,12-NQ ketyl radical. The absorption spectrum and the molar absorption coefficient of the 5,12-NQ ketyl radical were determined based on those of the p-phenylphenoxyl radical. It is shown that the quenching rate constants by phenol for triplet 5,12-NQ and other triplet paraquinones previously reported obey a Rehm-Weller relationship. The mechanism for the phenolic H-atom transfer to triplet paraquinones is interpreted in terms of coupled electron and proton transfer.

Anions↗
PubMed1996

Triplet state energy transfer between the primary donor and the carotenoid in Rhodobacter sphaeroides R-26.1 reaction centers exchanged with modified bacteriochlorophyll pigments and reconstituted with spheroidene.

The dynamics of triplet energy transfer between the primary donor and the carotenoid were measured on several photosynthetic bacterial reaction center preparations from Rhodobacter sphaeroides: (a) wild-type strain 2.4.1, (b) strain R-26.1, (c) strain R-26.1 exchanged with 13(2)-hydroxy-[Zn]-bacteriochlorophyll at the accessory bacteriochlorophyll (BChl) sites and reconstituted with spheroidene and (d) strain R-26.1 exchanged with [3-vinyl]-13(2)-hydroxy-bacteriochlorophyll at the accessory BChl sites and reconstituted with spheroidene. The rise and decay times of the primary donor and carotenoid triplet-triplet absorption signals were monitored in the visible wavelength region between 538 and 555 nm as a function of temperature from 4 to 300 K. For the samples containing carotenoids, all of the decay times correspond well to the previously observed times for spheroidene (5 +/- 2 microseconds). The rise times of the carotenoid triplets were found in all cases to be biexponential and comprised of a strongly temperature-dependent component and a temperature-independent component. From a comparison of the behavior of the carotenoid-containing samples with that from the reaction center of the carotenoidless mutant Rb. sphaeroides R-26.1, the temperature-independent component has been assigned to the buildup of the primary donor triplet state resulting from charge recombination in the reaction center. Arrhenius plots of the buildup of the carotenoid triplet states were used to determine the activation energies for triplet energy transfer from the primary donor to the carotenoid. A model for the process of triplet energy transfer that is consistent with the data suggests that the activation barrier is strongly dependent on the triplet state energy of the accessory BChl pigment, BChlB.

Bacteriochlorophylls↗
PubMed1997

G triplets located throughout a class of small vertebrate introns enforce intron borders and regulate splice site selection.

Splicing of small introns in lower eucaryotes can be distinguished from vertebrate splicing by the inability of such introns to be expanded and by the inability of splice site mutations to cause exon skipping-properties suggesting that the intron rather than the exon is the unit of recognition. Vertebrates do contain small introns. To see if they possess properties similar to small introns in lower eucaryotes, we studied the small second intron from the human alpha-globin gene. Mutation of the 5' splice site of this intron resulted in in vivo intron inclusion, not exon skipping, suggesting the presence of intron bridging interactions. The intron had an unusual base composition reflective of a sequence bias present in a collection of small human introns in which multiple G triplets stud the interior of the introns. Each G triplet represented a minimal sequence element additively contributing to maximal splicing efficiency and spliceosome assembly. More importantly, G triplets proximal to a duplicated splice site caused preferential utilization of the 5' splice site upstream of the triplets or the 3' splice site downstream of the triplets; i.e., sequences containing G triplets were preferentially used as introns when a choice was possible. Thus, G triplets internal to a small intron have the ability to affect splice site decisions at both ends of the intron. Each G triplet additively contributed to splice site selectivity. We suggest that G triplets are a common component of human 5' splice sites and aid in the definition of exon-intron borders as well as overall splicing efficiency. In addition, our data suggest that such intronic elements may be characteristic of small introns and represent an intronic equivalent to the exon enhancers that facilitate recognition of both ends of an exon during exon definition.

Animals↗
PubMed2004

Analysis of triplet repeat replication by two-dimensional gel electrophoresis.

Expansions of triplet repeats are responsible for more than 15 hereditary neurological disorders in humans. Triplet repeats are fairly stable when the number of elementary units is under approx 30, but become polymorphic in length with a clear bias for expansions when this threshold is exceeded. This results in the rapid addition of hundreds or even thousands of extra repeats and, ultimately, disease. The mechanisms of triplet repeat expansions are not yet understood. The role of several genetic processes, including replication, recombination, and repair, was suggested. However, given the swift accumulation of extra DNA material, DNA replication seems to be an intuitive candidate for generating expansions. Numerous data point to the aberrant replication of triplet repeats as a cause of triplet repeat expansions. Direct experimental proof of aberrant replication through triplet repeats was lacking. This encouraged us to study the mode of replication fork progression through triplet repeats in vivo. We analyzed the effects of triplet repeats on replication of bacterial or yeast plasmids using an approach called two-dimensional neutral/neutral gel electrophoresis of replication intermediates. This technique, originally developed for mapping replication origins, is also instrumental in defining replication pause sites. Using this technique, we were able to unambiguously demonstrate that expandable triplet repeats attenuate replication fork progression in vivo and get some insights into the mechanisms of repeat expansions.

Electrophoresis, Gel, Two-Dimensional↗
PubMedDate not supplied

Bimolecular hydrogen abstraction from phenols by aromatic ketone triplets.

Absolute rate constants for hydrogen abstraction from 4-methylphenol (para-cresol) by the lowest triplet states of 24 aromatic ketones have been determined in acetonitrile solution at 23 degrees C, and the results combined with previously reported data for roughly a dozen other compounds under identical conditions. The ketones studied include various ring-substituted benzophenones and acetophenones, alpha,alpha,alpha-trifluoroacetophenone and its 4-methoxy analog, 2-benzoylthiophene, 2-acetonaphthone, and various other polycyclic aromatic ketones such as fluorenone, xanthone and thioxanthone, and encompass n,pi*, pi,pi*(CT) and arenoid pi,pi* lowest triplets with (triplet) reduction potentials (E(red)*) varying from about -10 to -38 kcal mol(-1). The 4-methylphenoxyl radical is observed as the product of triplet quenching in almost every case, along with the corresponding hemipinacol radical in most instances. Hammett plots for the acetophenones and benzophenones are quite different, but plots of log k(Q) vs E(red)* reveal a common behavior for most of the compounds studied. The results are consistent with reaction via two mechanisms: a simple electron-transfer mechanism, which applies to the n,pi* triplet ketones and those pi,pi* triplets that possess particularly low reduction potentials, and a coupled electron-/proton-transfer mechanism involving the intermediacy of a hydrogen-bonded exciplex, which applies to the pi,pi* ketone triplets. Ketones with lowest charge-transfer pi,pi* states exhibit rate constants that vary only slightly with triplet reduction potential over the full range investigated; this is due to the compensating effect of substituents on triplet state basicity and reduction potential, which both play a role in quenching by the hydrogen-bonded exciplex mechanism. Ketones with arenoid pi,pi* states exhibit the fall-off in rate constant that is typical of photoinduced electron transfer reactions, but it occurs at a much higher potential than would be normally expected due to the effects of hydrogen-bonding on the rate of electron-transfer within the exciplex.

Calorimetry↗
PubMed2000

Cutaneous capillary hemangiomas of the eyelid, scalp, and digits in premature triplets.

PURPOSE: To document the unique occurrence of multiple cutaneous capillary hemangiomas in healthy triplets. METHODS: Case reports. RESULTS: Triplets born 6 weeks prematurely were noted at birth to have classic cutaneous capillary hemangiomas that enlarged in the first few months of life. At 3 months of age, triplet #1 manifested a small capillary hemangioma on the left index finger and a large hemangioma that involved the entire left upper eyelid and completely occluded the visual axis. Triplet #2 had a small hemangioma on the thumb and a large hemangioma on the scalp of the forehead. Triplet #3 displayed only a minor hemangioma of the right upper eyelid that did not threaten her vision. The parents of the triplets admitted having a history of periocular capillary hemangioma that spontaneously resolved. Triplet #1 was managed with oral corticosteroids, with dramatic regression of the mass and exposure of the visual axis. CONCLUSIONS: Cutaneous capillary hemangioma is usually a sporadic condition. We found this tumor in premature triplets whose parents had a history of a similar tumor. This suggests that hereditary and environmental factors may play a role in the development of this tumor. We advise that medical and family histories be obtained in all children with cutaneous capillary hemangioma.

Eyelids↗
PubMed1997

Rising trizygotic triplet rates in Japan, 1975-1994.

Zygosity of triplet births in Japan was estimated by Allen's equation with the assumption that the rate of dizygotic (DZ) triplets reflects that of twins. Whereas the DZ triplet rate increased during the period from 1975 to 1994, reflecting the increase in the DZ twinning rate in the period, monozygotic (MZ) triplet rates remained constant from 1975 (28 per million births) to 1994 (23). The trizygotic (TZ) triplet rate gradually increased from 1975 (18) up to 1985 (29), and rapidly increased thereafter to 1994 (202). The higher TZ triplet rate since 1986 is most likely attributed to the higher proportion of mothers treated with ovulation-inducing hormones and partially to in-vitro fertilization in Japan. As for maternal age, MZ triplet rates remained nearly constant for all the maternal age groups except the youngest and the oldest ones. On the other hand, TZ triplet rates increased up to the age group of 30-34 years and decreased thereafter in almost every year. The TZ rate in the age group of 30-34 years slowly increased from 1975 to 1988 (63 per million births) and rapidly increased thereafter (314 in 1994). The TZ rate was statistically significantly higher in the period 1986-1994 than in the period 1975-1985 in each of the nine districts in Japan. Geographical variations in the TZ rates in the latest period have drastically changed from those during the period from 1955-1959 and in 1974.

Adult↗
PubMed1991

Influence of clinical variables on triplet birth weight.

The small size of most reported triplet series has resulted in conflicting statements about the influence of several clinical variables on triplet birth weight. Therefore, obstetrical and neonatal data were collected on 196 mothers and their 580 infants (8 stillbirths excluded). Gestational age was based on the date of fertilization in 13 IVF triplets and on the date of ovulation in 90 medically induced triplets. Obstetrical and ultrasonic criteria were used to estimate the date of confinement in 93 spontaneous triplets. Birth weight appeared to be higher in males and with higher maternal parity, independent of gestational age. The apparent effect of medical technologies such as ovulation induction or IVF on combined triplet birth weight disappeared when maternal parity and fetal gender were controlled. Preeclampsia, maternal race and zygosity were not significantly associated with birth weight. While birth order did not significantly effect ultimate birth weight, the heaviest triplet did present first more often than would be expected by chance alone. Future evaluation of neonatal outcome data in multifetal gestations should control for gestational age, fetal gender and maternal parity. It appears that triplet birth weight is not affected by etiology, which is important given the significant impact of medical technologies.

Analysis of Variance↗
PubMedDate not supplied

Triplet morbidity and mortality in a large case series.

OBJECTIVE: A significant increase in the triplet birth rate has occurred recently. This rise is of concern, as these infants are historically reported to be at risk of adverse outcome. Thus, we examined the outcome of triplet births in a large contemporary case series. STUDY DESIGN: Since 1993, detailed clinical data have been collected on all patients admitted to our Neonatal Intensive Care Unit. We retrospectively analyzed this database to examine triplet outcome. RESULTS: A total of 51 consecutive sets of triplets were born over a 9-year period. The mean birth weight for triplets was 1789+/-505 g, mean gestational age was 32.6+/-2.7 weeks, with discordancy present in 17.6% of neonates. Complications of prematurity were infrequent. Triplet survival to discharge was 96%. CONCLUSIONS: This large contemporary case series of triplets demonstrates excellent survival with low associated morbidity. These data suggest that there may no longer be medical justification for offering selective fetal reduction to parents with triplet pregnancies.

Adult↗
PubMed1995

Intrauterine growth of triplets as estimated from liveborn birth weight data.

This study was conducted to estimate intrauterine growth of triplet pregnancies from liveborn birth weights. During the years 1975-92, 109 sets of triplets were born at our hospital. Ten sets were excluded because of either major fetal anomalies or fetal death of one or more of the fetuses. The remaining 99 sets of triplets consisted of 297 newborns that were weighted immediately after birth. The mean birth weight was plotted against gestational week. The estimated intrauterine growth of triplets, in contrast to singletons, exhibited neither an acceleration phase during the third trimester, nor a flattening of the growth curve during the last few weeks of the third trimester. The mean birth weight of triplets was slightly below the 10th centile for singletons at 38 weeks' gestation or later. We conclude that the growth of triplet fetuses as estimated from liveborn birth weights is slower than that of singletons. The diagnosis of intrauterine growth retardation in triplet pregnancies should be based on growth curves to be devised for triplet pregnancies.

Bias↗