Hairpin-Empowered Invasive Reaction Combined with Catalytic Hairpin Assembly Cascade Amplification for the Specific Detection of Single-Nucleotide Polymorphisms.

Single-nucleotide polymorphism (SNP) is widely used in the study of disease-related genes and in the genetic study of animal and plant strains. Therefore, SNP detection is crucial for biomedical diagnosis and treatment as well as for molecular design breeding of animals and plants. In this regard, this article describes a novel technique for detecting SNP using flap endonuclease 1 (FEN 1) as a specific recognition element and catalytic hairpin assembly (CHA) cascade reaction as a signal amplification strategy. The mutant target (MT) was hybridized with a biotin-modified upstream probe and hairpin-type downstream probe (DP) to form a specific three-base overlapping structure. Then, FEN 1 was employed for three-base overlapping structure-specific recognition, namely, the precise SNP site identification and the 5' flap of DP dissociation. After dissociation, the hybridized probes were magnetically separated by a streptavidin-biotin complex. Especially, the ability to establish such a hairpin-type DP provided a powerful tool that could be used to hide the cut sequence (CS) and avoid false-positive signals. The cleaved CS initiated the CHA reaction and allowed superior fluorescence signal generation. Owing to the high specificity of FEN 1 for single base recognition, only the MT could be distinguished from the wild-type target and mismatched DNA. Owing to the dual signal amplification, as low as 0.36 fM MT and 1% mutation abundance from the mixtures could be detected, respectively. Furthermore, it could accurately identify SNPs from human cancer cells, as well as soybean leaf genome extracts. This strategy paves the way for the development of more precise and sensitive tools for diagnosing early onset diseases as well as molecular design breeding tools.

Rationally Designed Dual Base Pair Mismatch Enables Toehold-Mediated Strand Displacement to Efficiently Recognize Single-Nucleotide Polymorphism without Enzymes.

The efficiency of the enzyme-free toehold-mediated strand displacement (TMSD) technique is often insufficient to detect single-nucleotide polymorphism (SNP) that possesses only single base pair mismatch discrimination. Here, we report a novel dual base pair mismatch strategy enabling TMSD biosensing for SNP detection under enzyme-free conditions when coupled with catalytic hairpin assembly (CHA) and fluorescence resonance energy transfer (FRET). The strategy is based on a competitive strand displacement reaction mechanism, affected by the thermodynamic stability originating from rationally designed dual base pair mismatch, for the specific recognition of mutant-type DNA. In particular, enzyme-free nucleic acid circuits, such as CHA, emerge as a powerful method for signal amplification. Eventually, the signal transduction of this proposed biosensor was determined by FRET between streptavidin-coated 605 nm emission quantum dots (605QDs, donor) and Cy5/biotin hybridization (acceptor, from CHA) when incubated with each other. The proposed biosensor displayed high sensitivity to the mutant target (MT) with a detection concentration down to 4.3 fM and led to high discrimination factors for all types of mismatches in multiple sequence contexts. As such, the application of this proposed biosensor to investigate mechanisms of the competitive strand displacement reaction further illustrates the versatility of our dual base pair mismatch strategy, which can be utilized for the creation of a new class of biosensors.

Research on spacecraft in orbit perception based on artificial neural networks and digital twin technology using grating arrays.

In order to improve the safety of spacecraft, the research on artificial neural network and digital twin technology based on, to our best knowledge, a novel fiber Bragg grating (FBG) sensor array is proposed for intelligent sensing monitoring of spacecraft on-orbit collisions. Femtosecond FBG arrays were fabricated on the novel oxide-doped fiber by point-by-point writing technique. The femtosecond FBG is analyzed using the time-dependent perturbation theory of quantum mechanics. The FBG array can achieve high-temperature measurement of 1100 °C and large strain measurement of 15000 µÎµ. The sensing arrays were deployed on the surface of the spacecraft. Constructed the multi-layer perceptron neural network structure and convolutional neural network structure. 1200 samples were trained. Conducted model accuracy testing. The accuracy rate is above 98%, and accuracy verification has been implemented. The digital twin model was designed based on various data such as strain and temperature of the spacecraft structure under impact monitored by FBG sensors. A precise mapping has been formed between the physical entities of spacecraft and digital twins. Empower spacecraft with functions such as self-monitoring, judgment, and response. To ensure the stable and safe operation of spacecraft.

Solid rocket motor propellant health monitoring based on oxide-doped curved long-period fiber grating.

A kind of curved long-period fiber grating(CLPFG) engraved by CO2 laser based on oxide-doped fiber was designed to monitor the structural integrity of propellant. The mechanical damage characteristics of the propellant were analyzed. The sensor model is constructed and the refractive index modulation characteristics of the CLPFG are analyzed. The strain coupling characteristics and the strain transfer efficiency of the interface between the CLPFG and the propellant are clarified. Propellant modules with implanted CLPFG were fabricated. The novel grating sensor has been effectively coated and structurally packaged. Conducted experiments on strain and temperature of propellant modules. The large strain measurement of propellant from 0 µÎµ to 24000 µÎµ is realized. Solved the thorny problem of large strain measurement for propellants. In addition, the temperature discrimination measurement in the temperature range of 30 ℃ to 250 ℃ can be realized. Sensor exhibit extremely high stability characteristics and has good compatibility with propellants. The sensor implantation and extraction structure has been designed to improve the survival rate of the sensor inside the solid rocket motors (SRM). Sensors can accurately measure the mechanical and thermal state parameters of propellants, providing effective data support for the health management of SRM.

Photonic generation of dual-band triangular chirps utilizing a monolithic integrated mutual injection laser and application in radars.

We propose and demonstrate a dual-band microwave photonic radar scheme based on a monolithic integrated mutual injection laser. Based on the photon-photon resonance (PPR) and the gain switching effect of the integrated laser, the C-/X-band triangular chirp signals with high-quality and comparable power at 4.75-5.25 GHz and 9.5-10.5 GHz are generated. In the current proof-of-concept experiment, the range resolution of the dual-band chirp signals can reach 16.9 cm, compared with the single-band chirp signal that cannot distinguish the targets. Through the application of a single integrated device and a transceiver module sharing a set of antennas, the dual-band microwave photonic radar system scheme improves the system integration.

Equivalent circuit model of the traveling wave electrode for lithium niobate thin film Mach-Zehnder modulators.

We propose an equivalent circuit model of the traveling wave electrode for lithium niobate thin film (TFLN) Mach-Zehnder modulators, in which the distributed capacitance and conformal mapping techniques are applied to calculate the microwave refractive index, microwave loss, and characteristic impedance. Their accuracies are verified by comparing with the results of the finite element method, and the relative errors are less than 3.282%, 1.776%, and 5.334%, respectively. The influence of the electrode's structural parameters on the modulation performances is analyzed, and a 3 dB modulation bandwidth around 84 GHz with an 8-mm-long traveling wave electrode is obtained.

Interface debonding monitoring of solid rocket motor based on femtosecond grating array.

During the whole life cycle of solid rocket motor (SRM), shell damage and propellant interface debonding will occur, which will destroy the structural integrity of SRM. Therefore, it is necessary to monitor the SRM health status, and the existing nondestructive testing technology and the designed optical fiber sensor cannot meet the monitoring requirements. In order to solve this problem, this paper uses femtosecond laser direct writing technology to write high contrast short femtosecond grating array. A new packaging method is proposed to enable the sensor array to measure 9000 µÎµ. It solves the grating chirp phenomenon caused by stress concentration in the SRM, and breaks through the key technology of fiber optic sensor implantation in the SRM. The shell pressure test and strain monitoring inside the SRM during long-term storage are realized. For the first time, the experiments of tearing and shearing specimens were simulated. Compared with the results of computed tomography, it proves the accuracy and progressiveness of implantable optical fiber sensing technology. Combined with theory and experiment, the problem of SRM life cycle health monitoring is solved.

High-purity linearly frequency-modulated signal generation based on the integrated semiconductor laser subject to the dynamical optoelectrical feedback.

A novel photonic method of linearly frequency-modulated (LFM) signal generation with high purity based on the monolithically integrated semiconductor laser (MISL) subject to the dynamical optoelectrical feedback is proposed and demonstrated in this paper. In this approach, the MISL is firstly operated in period-one state. By introducing the dynamical optoelectrical feedback to modulate the MISL, the generated LFM signals would be constantly optimized as long as the delay of the feedback loop is matched with the repetition period of the LFM signal. In this system, no additional high-speed external modulator, high-frequency electrical LFM oscillator are required, highly simplifying the framework and reducing the power consumption. In the current proof-of-concept experiment, one LFM signal with the bandwidth as large as 5.6 GHz is generated and the corresponding frequency comb contrast can be drastically improved by 51 dB. Furthermore, the effect of the delay mismatch is also discussed in this paper.

Millimeter-wave generation based on a monolithic dual-wavelength DFB laser with four phase-shifted sampled gratings and equivalent chirp technology.

A dual-wavelength DFB laser array based on four phase-shifted grating and equivalent chirp technology is first proposed, fabricated, and experimentally demonstrated. The dual-wavelength emitting is achieved by symmetrically introducing two π phase shifts into a chirped four phase-shifted sampled grating cavity. Meanwhile, the beating signal of the dual-wavelength output is stabilized by applying an electro-absorption modulator integrated at the rear of the cavity. Under different grating chirp rates, a series of RF signals from 66.8 GHz to 73.6 GHz with a linewidth of less than 210 kHz is obtained.

Interleukin-4 activates the PI3K/AKT signaling to promote apoptosis and inhibit the proliferation of granulosa cells.

The inflammatory microenvironment has been demonstrated to play a role in folliculogenesis, ovulation and premature ovarian failure (POF), as well as infertility. In this study, we aimed to explore the role of inflammation in modulating growth and apoptosis in granulosa cells (GCs), the main components of ovarian follicles. ELISA was used to analyze the levels of inflammatory factors (IL-1ß, IL-4, IL-6 and IL-10) in follicular fluid samples and GCs derived from POF patients and healthy normal individuals. CCK-8, flow cytometry and TUNEL assays were used to assess the effect of IL-4 on GC growth and apoptosis. Western blotting was used to examine the effect of IL-4 on the activation of PI3K/Akt, Erk1/2 and Jnk signaling. The results showed that IL-4, IL-1ß and IL-6 levels were increased in follicular fluid samples and GCs derived from POF patients compared with those from healthy individuals. GC growth was weakened when cells were treated with IL-4, while apoptosis was increased. In addition, IL-4 increased the level of p-Akt/Akt in GCs. In addition, LY294002, an inhibitor of PI3K, abolished the effect of IL-4 by inhibiting GC growth and promoting apoptosis. In summary, this study demonstrated that IL-4 levels were increased in POF samples and that IL-4 could inhibit GC growth and induce GC apoptosis by activating PI3K/Akt signaling.

Four-channel all-optical wavelength conversion unit based on nonlinear effect of three-section monolithically integrated semiconductor lasers.

A simple and highly efficient four-channel all-optical wavelength conversion based on four-wave mixing effect of the directly modulated three-section monolithically integrated semiconductor laser is proposed and experimentally investigated. For this wavelength conversion unit, the spacing of the wavelength can be adjusted by tuning the bias current of the lasers and setting it to be 0.4 nm (50 GHz) as a demonstration is this work. A 50 Mbps 16-QAM signal centers at 4-8 GHz is experimentally switched to a targeted path. Up- or downconversion depends on a wavelength-selective switch, and the conversion efficiency can reach up to -2 to 0 dB. This work provides a new technology for photonic radio-frequency switching matrix and contributes to the integrated implementation of satellite transponders.

Simple multi-band linearly frequency-modulated signal generation with a multiplying bandwidth based on a gain-switching laser.

Multi-band linearly frequency-modulated (LFM) signal generation with a multiplying bandwidth is proposed and experimentally demonstrated. It is a simple photonics method based on the gain-switching state in a distributed feedback semiconductor laser without a complex external modulator and high-speed electrical amplifiers. With N comb lines, the carrier frequency and bandwidth of generated LFM signals are N times those of the reference signal. (N is the number of comb lines.) The number of bands and time-bandwidth products (TBWPs) of the generated signals could be easily adjusted by tuning the reference signal from an arbitrary waveform generator. Three-band LFM signals with carrier frequencies ranging from the X-band to K-band are given as an example, and the TBWP up to 20000. The results of auto-correlations of the generated waveforms are also given.

Interaction of air pollution and meteorological factors on IVF outcomes: A multicenter study in China.

BACKGROUND: Previous studies revealed associations between air-pollutant exposure and in vitro fertilization (IVF) outcomes. However, modification effects of air pollution on IVF outcomes by meteorological conditions remain elusive. METHODS: This multicenter retrospective cohort study included 15,217 women from five northern Chinese cities during 2015-2020. Daily average concentrations of air pollutants (PM2.5, PM10, O3, NO2, SO2, and CO) and meteorological factors (temperature, relative humidity, wind speed, and sunshine duration) during different exposure windows were calculated as individual approximate exposure. Generalized estimating equations models and stratified analyses were conducted to assess the associations of air pollution and meteorological conditions with IVF outcomes and estimate potential interactions. RESULTS: Positive associations of wind speed and sunshine duration with pregnancy outcomes were detected. In addition, we observed that embryo transfer in spring and summer had a higher likelihood to achieve a live birth compared with winter. Exposure to PM2.5, SO2, and O3 was adversely correlated with pregnancy outcomes in fresh IVF cycles, and the associations were modified by air temperature, relative humidity, and wind speed. The inverse associations of PM2.5 and SO2 exposure with biochemical pregnancy were stronger at lower temperatures and humidity. Negative associations of PM2.5 with clinical pregnancy were only significant at lower temperatures and wind speeds. Moreover, the effects of O3 on live birth were enhanced by higher wind speed. CONCLUSIONS: Our results suggested that the associations between air-pollutant exposure and IVF outcomes were modified by meteorological conditions, especially temperature and wind speed. Women undergoing IVF treatment should be advised to reduce outdoor time when the air quality was poor, particularly at lower temperatures.

Hydrophobically Associating Polyacrylamide "Water-in-Water" Emulsion Prepared by Aqueous Dispersion Polymerization: Synthesis, Characterization and Rheological Behavior.

The hydrophobically associating polyacrylamide (HAPAM) is an important kind of water-soluble polymer, which is widely used as a rheology modifier in many fields. However, HAPAM products prepared in a traditional method show disadvantages including poor water solubility and the need for hydrocarbon solvents and appropriate surfactants, which lead to environmental pollution and increased costs. To solve these problems, we reported a novel kind of HAPAM "water-in-water" (w/w) emulsion and its solution properties. In this work, a series of cationic hydrophobic monomers with different alkyl chain lengths were synthesized and characterized. Then, HAPAM w/w emulsions were prepared by the aqueous dispersion polymerization of acrylamide, 2-methylacryloylxyethyl trimethyl ammonium chloride and a hydrophobic monomer. All these emulsions can be stored more than 6 months, showing excellent stability. An optical microscopy observation showed that the particle morphology and the particle size of the HAPAM emulsion were more regular and bigger than the emulsion without the hydrophobic monomer. The solubility tests showed that such HAPAM w/w emulsions have excellent solubility, which took no more than 180 s to dilute and achieve a homogeneous and clear solution. The rheology measurements showed that the HAPAM association increases with a hydrophobe concentration or the length of hydrophobic alkyl chains, resulting in better shear and temperature resistances. The total reduced viscosity was 124.42 mPa·s for cw101, 69.81 mPa·s for cw6-1, 55.38 mPa·s for cw8-0.25, 48.95 mPa·s for cw12-0.25 and 28 mPa·s for cw16-0.25 when the temperature increased from 30 °C to 90 °C. The cw8-2.0 that contains a 2 mol% hydrophobe monomer has the lowest value at 19.12 mPa·s due to the best association. Based on the excellent stability, solubility and rheological properties, we believe that these HAPAM w/w emulsions could find widespread applications.

Low-power RF signal detection with wideband range based on an optically injected optoelectronic oscillator.

A novel method to detect a low-power radio-frequency (RF) signal with ultra-wide frequency range based on an optically injected optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The optical injection to a distributed feedback (DFB) laser has the advantages of amplifying one sideband of the modulated optical signal selectively and a wide tunable frequency range. The detection upper range that reaches up to 26 GHz and can be improved theoretically. To the best of the authors' knowledge, this is the widest detection range based on an OEO. At the same time, the detection characteristics are good. The sensitivity of the system is -92 dBm and the maximum gain is 12.18 dB at 15.047 GHz. Considering the real application of the detection system, the properties such as dynamic range and performance for detecting a modulated RF signal are also investigated.

Comparative clinical outcome following individualized follitropin delta dosing in Chinese women undergoing ovarian stimulation for in vitro fertilization /intracytoplasmic sperm injection.

BACKGROUND: To compare the efficacy and safety of follitropin delta in its individualized fixed-dose regimen with follitropin alfa in a conventional adjustable dosing regimen in Chinese women.  METHODS: This was a subgroup analysis of the randomized, multi-center, assessor-blind, non-inferiority trial (GRAPE) including 759 Chinese women (aged 20-40 years) recruited in 16 reproductive medicine clinics in China. Women were randomized in a 1:1 ratio to be treated with either follitropin delta dose based on anti-Müllerian hormone (AMH) and body weight or conventional dosing with follitropin alfa following a gonadotropin-releasing hormone (GnRH) antagonist protocol. The primary outcome was ongoing pregnancy rate assessed 10-11 weeks after embryo transfer in the fresh cycle (non-inferiority margin -10.0%). RESULTS: 378 in the follitropin delta group and 381 in the follitropin alfa group were randomized and exposed. Non-inferiority was confirmed with respect to ongoing pregnancy with rates of 31.0% vs. 25.7% for follitropin delta compared to follitropin alfa, estimated mean difference of 5.1% (95% confidence interval (CI) -1.3% to 11.5%). The clinical pregnancy rate (35.4% vs. 31.5%, P = 0.239) and live birth rate (31.0% vs. 25.5%, P = 0.101) were comparable between the follitropin delta group and the follitropin alfa group. Overall, the individualized follitropin delta treatment resulted in fewer oocytes retrieved compared to follitropin alfa treatment (10.3 ± 6.2 vs. 12.5 ± 7.5, P < 0.001), which was mainly due to fewer oocytes (10.5 ± 6.4 vs. 13.9 ± 7.8) in women with AMH ≥ 15 pmol/L. Accordingly there was a lower incidence of early ovarian hyper-stimulation syndrome (OHSS) and/or preventive interventions (6.1% vs. 11.0%, P = 0.013). A daily follitropin delta dose of 10.2 µg (95% CI: 9.3-11.2 µg) was estimated to provide the same number of oocytes retrieved as a starting dose of 150 IU/d of follitropin alfa. CONCLUSION: Follitropin delta in its individualized fixed-dose regimen showed similar efficacy and improved safety compared with follitropin alfa in a conventional adjustable dosing regimen in Chinese women. CLINICAL TRIAL REGISTRATION NUMBER: NCT03296527.

Grass Carp Reovirus triggers autophagy enhancing virus replication via the Akt/mTOR pathway.

Autophagy impacts the replication cycle of many viruses. Grass Carp Reovirus (GCRV) is an agent that seriously affects the development of the grass carp aquaculture industry. The role of autophagy in GCRV infection is not clearly understood. In this study, we identified that GCRV infection triggered autophagy in CIK cells, which was demonstrated by transmission electron microscopy, the conversion of LC3B I to LC3B II and the level of autophagy substrate p62. Furthermore, we found that GCRV infection activated Akt-mTOR signaling pathway, and the conversion of LC3B I to LC3B II was increased by inhibiting mTOR with rapamycin (Rap) but decreased by activating Akt with insulin. We then assessed the effects of autophagy on GCRV replication. We found that inducing autophagy with Rap promoted GCRV proliferation but inhibiting autophagy with 3 MA or CQ inhibited GCRV replication in CIK cells. Moreover, it was found that enhancing Akt-mTOR activity by insulin, GCRV VP7 protein and viral titers of GCRV were decreased. Collectively, these results indicated that GCRV infection induced autophagy involved in GCRV replication via the Akt-mTOR signal pathway. Thus, new insights into GCRV pathogenesis and antiviral treatment strategies are provided.

Adverse obstetric and perinatal outcomes in 2333 singleton pregnancies conceived after different endometrial preparation protocols: a retrospective study in China.

BACKGROUP: Frozen-thawed embryo transfer is rising worldwide. One adverse effect of programmed frozen embryo transfer (FET) reported in some studies is an increased risk of adverse obstetric and perinatal outcomes. Meanwhile, body mass index (BMI) also has adverse effect on obstetric and perinatal outcomes. In this study, we investigated that the influence of different endometrial preparation protocols on obstetric and perinatal outcomes and the role of BMI in it. METHOD: This retrospective cohort study included 2333 singleton deliveries after frozen-thaw embryo transfer at our centre between 2014 and 2021, including 550 cycles with programmed FET, 1783 cycles with true natural cycle FET (tNC-FET). In further analysis according to BMI grouped by Asian criterion, group A (18.5 kg/m2 ≤ BMI < 24.00 kg/m2) included 1257 subjects, group B (24 kg/m2 ≤ BMI < 28.00 kg/m2) included 503 subjects and group C (BMI ≥ 28 kg/m2) included 573 subjects. Baseline characteristics of the two groups were compared and analyzed. Binary logistic regression analyses were performed to explore the association between obstetric and perinatal outcomes and endometrial preparation protocols. RESULTS: There were no significant differences in the placenta previa, gestational diabetes mellitus(GDM), preterm premature rupture of membranes (PPROM), cesarean section (CS) and macrosomia between the tNC-FET and programmed FET groups (P > 0.05). The programmed FET cycles were associated to a higher risk of pregnancy-induced hypertension (PIH) compared with the tNC-FET cycles (7.3% vs 4.4%, crude OR 1.71[1.16-2.54]; adjusted OR 1.845[1.03-3.30]). After dividing the patients into three groups according to the BMI, The programmed FET cycles were associated to a higher risk of PIH in group C (14.4% vs 6.2%, crude OR 2.55 [1.42-4.55]; adjusted OR 4.71 [1.77-12.55]) compared with the tNC-FET cycles. But there was no statistically significant difference in group A and group B. Programmed FET group compared with the tNC-FET group, the risk of PIH increase as the body mass index increase. CONCLUSION: This study showed a tendency toward increasing risk of PIH in programmed FET cycle compared with the tNC-FET cycle, and the risk of PIH increases as BMI increases. Increased risk of preterm birth and low birth weight is linked to increased risk of PIH.

Serum anti-Müllerian hormone levels are associated with early miscarriage in the IVF/ICSI fresh cycle.

BACKGROUND: Anti-Müllerian hormone (AMH) is used as a biomarker to estimate ovarian reserve. The relationship between AMH and early miscarriage of in vitro fertilization (IVF) is still inconclusive. This study aimed to explore whether serum AMH levels are associated with early miscarriage rates after in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) with fresh embryo transfer (ET). METHODS: This retrospective cohort study included 2246 patients undergoing their first oocyte retrievals for IVF/ICSI with fresh embryos transferred to Tianjin Central Hospital of Gynecology Obstetrics between May 2018 and March 2020. The serum AMH levels of the patients were measured within 12 months before the IVF/ICSI cycles. All women were divided into a low-AMH group, medium-AMH group and high-AMH group. Binary logistic regression was applied to confirm whether the serum AMH level was associated with the risk of early miscarriage independent of potential confounders, such as age, body mass index (BMI), duration of infertility, main diagnosis, history of internal medicine diseases, number of oocytes retrieved and high-quality embryo rate. RESULTS: The early miscarriage rate was significantly lower in the medium-AMH group than in either the low-AMH or high-AMH group among young (< 35 years) women (P = 0.015). In women above 35 years of age, the early miscarriage rates in the three AMH groups were not significantly different. Young women with high serum AMH levels had a significantly higher risk of early miscarriage regardless of age or other potential confounders (adjusted odds ratio (OR) 2.382, 95% confidence interval (CI) 1.246 to 4.553, P = 0.009). The results remained similar after restricting the analysis to women without polycystic ovary syndrome (PCOS). CONCLUSIONS: With a high AMH level, young women had a higher risk of early miscarriage than women with a medium AMH level in their first IVF/ICSI treatment. In young women, serum AMH levels were independently associated with the risk of early miscarriage after IVF-ET treatment. Serum AMH levels might be a valuable marker to estimate the risk of early miscarriage. It is worth noting to the clinical value of AMH.

Previous caesarean delivery and the presence of caesarean scar defects could affect pregnancy outcomes after in vitro fertilization frozen-thawed embryo transfer: a retrospective cohort study.

BACKGROUND: Due to various iatrogenic and social factors, the global caesarean delivery (CD) rate has risen sharply in the past 30 years. It is more complicated and dangerous for women with a scarred uterus to experience pregnancy again than for women with a previous vaginal delivery (VD). In this study we investigated the impact of previous caesarean delivery (CD) and caesarean scar defects (CSDs) on pregnancy outcomes after in vitro fertilization frozen-thawed embryo transfer (IVF-FET). METHODS: We conducted a retrospective cohort study that included 1122 women aged < 40 years who had a history of only one parturition (after 28 weeks of pregnancy) and who underwent their first FET cycle between January 2014 and January 2020. Patients were divided into the CD group, VD group, and CSD group. Thereafter, according to the number of transferred embryos, the CD, VD, and CSD groups were divided into the single embryo transfer (SET) group and the double embryo transfer (DET) group. Outcome measures in this study were live birth, clinical pregnancy, multiple pregnancy, ectopic pregnancy, pregnancy loss, pregnancy complications, preterm birth, and neonatal birth weight. Multivariate logistic regression was performed to evaluate the relationship between pregnancy outcomes and CD. RESULTS: In SET patients, the clinical pregnancy and live birth rates were decreased in the CSD group compared with the VD and CD groups. In DET patients, the clinical pregnancy and live birth rates were significantly lower in theCSD group than in the CD and VD groups. After adjustment for confounders, previous CD and CSD were associated with a significantly lower clinical pregnancy rate and live birth rate than previous VD in the total sample. This effect was observed in DET patients, but not in SET patients. Additionally, DET patients with previous CD had a significantly higher multiple pregnancy rate (AOR = 0.47, 95% CI = 0.29, 0.75, P = 0.002) than those with previous VD, but no significant associations were observed in CSD and multiple pregnancies (AOR = 0.55, 95% CI = 0.23, 1.34, P = 0.192) between DET patients with CD and those with VD after adjusting for potential confounders. CONCLUSIONS: Our study showed that during an FET cycle, previous CD and the presence of a CSD could negatively affect pregnancy outcomes especially in DET patients.