The goal of this clinical trial is to evaluate the effect of laser assisted hatching (LAH) on pregnancy outcomes, with live birth rate as the primary outcome, in advanced age infertile women aged ≥35 years who are undergoing non-donor IVF/ICSI cycles and planning vitrified-warmed embryo transfer. It also aims to monitor the safety of LAH and assess various secondary pregnancy and neonatal outcomes. The main questions it aims to answer are: Does laser assisted hatching improve the live birth rate in advanced age women undergoing vitrified-warmed embryo transfer? Does laser assisted hatching affect secondary outcomes including implantation rate, biochemical pregnancy rate, clinical pregnancy rate, ectopic pregnancy rate, ongoing pregnancy rate, miscarriage rate, multiple pregnancy rate, preterm birth rate, and rates of obstetric and neonatal complications as well as congenital anomalies? Researchers will compare the Laser Assisted Hatching (LAH) Group to the Control Group (without LAH) to see if LAH can improve pregnancy outcomes in the study population. Participants will: * Be randomly assigned to either the LAH Group or the Control Group at a 1:1 ratio, stratified by age (\<40 years/≥40 years) and embryo stage (cleavage stage/blastocyst) using stratified block randomization. * Undergo the first or second frozen-thawed embryo transfer cycle, with transferred embryos meeting the quality criteria (cleavage-stage embryos: Grade I, Grade II, or CP and above; blastocysts: 4BC/CB and above). * Receive embryo vitrification and warming after routine fertilization and culture; LAH Group will undergo LAH (thinning zona pellucida for cleavage-stage embryos, removing 1/4-1/3 of zona pellucida circumference for blastocysts) in G2 medium after embryo thawing, while Control Group will not receive assisted hatching. * Have endometrial preparation by natural, ovulatory, or hormone replacement cycles as appropriate, and 1-2 viable embryos will be transferred under ultrasound guidance within 3 hours after thawing, followed by routine luteal support after transfer. * Complete follow-up at multiple time points: 12-15 days after embryo transfer (serum β-hCG test), 28 days after embryo transfer (transvaginal ultrasound), 12 weeks of gestation (ultrasound), 28 weeks of gestation (ultrasound), and 1 month after delivery (collection of delivery and neonatal information). * Provide demographic, clinical, and embryological baseline data, as well as various outcome data during the study period. * Undergo regular monitoring of vital signs, laboratory test results, and adverse events, with key prevention and control of specific risks related to LAH such as embryo damage and multiple pregnancy.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
916
Laser assisted hatching will be performed on vitrified-warmed embryos prior to embryo transfer according to standard laboratory procedures. For cleavage-stage embryos, the zona pellucida will be thinned; for blastocysts, 1/4-1/3 of the zona pellucida circumference will be removed, and the operation will be performed in G2 medium after embryo thawing.
Live birth rate
Live birth rate is defined as the proportion of all enrolled participants who achieved a live birth, defined as the delivery of a live infant at ≥28 weeks of gestation with any signs of life (e.g., heartbeat, respiration).
Time frame: From enrollment to the delivery (≥28 weeks of gestation)
Ongoing pregnancy rate
The proportion of participants enrolled in the study who experienced an ongoing pregnancy, defined as the confirmation of an intrauterine viable fetus via ultrasound examination at 12 weeks of gestation.
Time frame: From enrollment to 12 weeks of gestation
Biochemical pregnancy rate
The proportion of participants enrolled in the study who experienced a biochemical pregnancy, defined as a serum HCG level ≥25 IU/L measured 14 or 15 days after embryo transfer.
Time frame: From enrollment to 12 days (blastocyst), 14 days (D3), or 15 days (D2) after embryo transfer
Ectopic pregnancy rate
The proportion of participants enrolled in the study who experienced an ectopic pregnancy, defined as the detection of an extrauterine gestational sac (including heterotopic pregnancy) via ultrasound examination after embryo transfer.
Time frame: From enrollment to 28 days after embryo transfer
Neonatal complication rate
The proportion of participants who achieved a live birth and delivered a newborn with neonatal complications.
Time frame: From enrollment to 1 month after delivery
Macrosomia rate
The proportion of participants who achieved a live birth and delivered a newborn with a birth weight of ≥4000g.
Time frame: From enrollment to the delivery
Low birth weight rate
The proportion of participants who achieved a live birth and delivered a newborn with a birth weight of less than 2500g.
Time frame: From enrollment to the delivery
Miscarriage rate
The proportion of participants who experienced a clinical pregnancy and subsequently had a spontaneous pregnancy loss before 28 weeks of gestation.
Time frame: From enrollment to 28 weeks of gestation
Clinical pregnancy rate
The proportion of participants enrolled in the study who experienced a clinical pregnancy, defined as the confirmation of an intrauterine gestational sac via ultrasound examination 28 days after embryo transfer.
Time frame: From enrollment to 28 days after embryo transfer
Preterm birth rate
The proportion of participants who achieved a live birth and delivered between 28 and 36⁺⁶ weeks of gestation.
Time frame: From enrollment to the delivery
Implantation rate
The proportion of all transferred embryos that developed into an intrauterine gestational sac, as confirmed by ultrasound examination 28 days after embryo transfer.
Time frame: From enrollment to 28 days after embryo transfer
Congenital malformation rate
The proportion of participants who achieved a live birth and delivered a newborn diagnosed with a congenital malformation according to the International Classification of Diseases (ICD-10).
Time frame: From enrollment to 1 month after delivery
Multiple pregnancy rate
The proportion of participants enrolled in the study diagnosed with multiple pregnancy, defined as the confirmation of ≥2 intrauterine gestational sacs via ultrasound examination 28 days after embryo transfer.
Time frame: From enrollment to 28 days after embryo transfer
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