Duration of freezing embryos and perinatal outcomes
Research type
Research Study
Full title
The impact of duration of freezing of IVF embryos on pregnancy and perinatal outcomes – analysis of U.K. national data
IRAS ID
326303
Contact name
Edwin Amalraj Raja
Contact email
Sponsor organisation
University of Aberdeen
Duration of Study in the UK
0 years, 11 months, 30 days
Research summary
Objective: The aim of the study is to investigate an association between the duration of the embryo(s) storage and having a live birth as well as a healthy baby.
Database: HFEA-linked data on all women who underwent IVF involving fresh and frozen embryos in the UK between 2000 and 2021 will be used. A unique number is given for each woman who undergoes IVF treatment. A complete cycle of IVF for each woman will be identified based on the woman’s ID and cycle ID.
Ethical approval: Ethical approval will be obtained from an NHS Research Ethics Committee
Population: All women who have undergone in-vitro fertilisation treatment in the UK and who have had at least one episode of a frozen embryo transfer will be included in the study. We will exclude those who have had IVF treatment before the age of 18 years old or after 50 years old.
Exposure variable: The length of time an embryo was frozen (in months) will be calculated as the interval between the date of embryo freezing and the date of embryo transfer and will be used as a continuous and categorical variable in separate analyses.
The Outcomes will be 1. Live birth 2. gestational age at birth 3. birthweight at delivery 4. birthweight adjusted for gestational age and gender 5. congenital anomaly.
Statistical analysis
A population-averaged model using Generalized Estimating Equations (GEE) will be used to explore associations between duration of embryo freezing and live birth and perinatal outcomes after frozen embryo transfer. The GEE will estimate the effect assuming an exchangeable correlation structure, and 95% Confidence Intervals (CI) estimated using robust standard errors.REC name
South Central - Oxford C Research Ethics Committee
REC reference
23/SC/0237
Date of REC Opinion
7 Jul 2023
REC opinion
Favourable Opinion