Health of Frozen Transferred Versus Fresh Transferred Children
Health of Frozen Transferred Versus Fresh Transferred Children
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.
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.
Inclusion Criteria:

 -  Live babies born from the first transfer of both freeze-only and fresh embryo transfer
 group from our Freeze-only study.

 -  Parents agree to participate in the study.

 Exclusion Criteria:

 -  Babies died after perinatal period.