Health of Frozen Transferred Versus Fresh Transferred Children
Condition: Infertility; IVF
MeSH terms: Infertility
Study type: Observational

Summary: 
      In order to give strong recommendation on the efficacy and safety of fresh versus frozen
      embryo transfer, we conduct this study in order to investigate the physical and mental
      development of children from fresh versus frozen embryo transfer. Based on our Freeze-only
      study (Vuong et al., 2018), the women without polycystic ovary syndrome undergoing the first
      or second IVF were randomly assigned to receive either fresh or frozen embryos on day 3 after
      oocyte retrieval, which leads to the similarity in characteristics of these two groups.
      Hence, the result from analysing these offsprings would be preciously valuable.
    

Detailed description: 
      Since the first live birth after the transfer of a frozen-thawed embryo reported in 1984,
      cryopreservation has been considered as an enormous revolution in assisted reproductive
      technology (ART). It is observed that the trend of ART cycles using frozen embryo transfer is
      on the increase, which leads to a great deal number of children born from frozen embryos.
      This is the commencement of 2 embryo transfer strategies, the first one is transferring the
      fresh embryos, the other is freezing all the embryos and transfer them in the next cycle.

      Comparing these two strategies, up till now, there are 4 published randomized control trials
      (RCTs) indicating different methods for certain groups of patients (Chen et al., 2016; Shi et
      al., 2018; Vuong et al., 2018; Wei et al., 2019). Regarding the efficacy, the freeze-all
      strategy outweighs the fresh embryo transfer in women with polycystic ovary syndrome (PCOS).
      While that efficacy gets a controversy in non-PCOS or ovulatory patients; two groups of
      authors indicated that these 2 strategies are equally effective, while the other group claims
      that the better result goes to cycles with frozen embryos. In term of safety, the rate of
      ovarian hyperstimulation syndrome (OHSS) is the equivalent or lower in the freeze-all group,
      which implies the important role of embryo-freezing in avoiding maternal risk. The question
      that whether freezing the embryos exerts effect on offspring is not thoroughly understood.
      The mostly used parameter in evaluating the safety of children is the perinatal status of
      infants, not the development of these children.

      Searching literature, in 2010, S. Pelkonen published a large cohort study indicating that
      freezing the embryos do not change the rate of prematurity, low birthweight and being small
      for gestational age (Pelkonen et al., 2010). Looking further in our freeze-only study, our
      sub-analysis indicates that the livebirth weight of infants born from frozen embryos is 300
      gram heavier than that from fresh embryos (Vuong et al., 2018). Following 4 studies comparing
      fresh and frozen embryo transfer, children from frozen embryos are similar or higher in term
      of newborn weight, and there is no study investigate the onward development of childrens born
      from these two strategies. The only proof on the development of children born from fresh
      verus frozen embryo is from one study with no randomization which states that children from
      fresh and frozen embryos share similar academic performance at the age 15-16 (Spangmose et
      al., 2019). We found no study investigate the impact of different embryo transfer strategies
      on the growth of children resulting from either fresh or frozen embryos.

      In order to give strong recommendation on the efficacy and safety of fresh versus frozen
      embryo transfer, we conduct this study in order to investigate the physical and mental
      development of children from fresh versus frozen embryo transfer. Based on our Freeze-only
      study (Vuong et al., 2018), the women without polycystic ovary syndrome undergoing the first
      or second IVF were randomly assigned to receive either fresh or frozen embryos on day 3 after
      oocyte retrieval, which leads to the similarity in characteristics of these two groups.
      Hence, the result from analysing these offsprings would be preciously valuable.
    

Intervention name(s): Developmental score according to The Ages & Stages Questionnaires®, Third Edition - ASQ®-3; Physical development and General Health; Developmental Red flags
Intervention type(s): Other; Other; Other
Intervention description(s): Ages & Stages Questionnaires®, Third Edition (ASQ®-3) is a developmental screening tool designed for use by early educators and health care professionals. It relies on parents as experts, is easy-to-use, family-friendly and creates the snapshot needed to catch delays and celebrate milestones.; Physical development and General health examination; Developmental Red flags Questionnaires
Observational model: Other
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Live babies born following the frozen embryo transfer and fresh embryo transfer from our
        Freeze-only study (NCT02471573)
      
Keywords: Fresh transfer, freeze-only, ASQ-3, health of children