Neonatal outcome of 99 children conceived after transfer of vitrified day 5 embryos compared to children born after intracytoplasmic sperm injection.

introduction: Since the vitrification technique is increasedly used and controlled
outcome studies are still scarce, it is important to collect follow-up data
on children conceived with this method in order to evaluate the potential toxicity
of the cryoprotectants to the embryo and future child. The major objective
of this study was to determine if the vitrification procedure might affect health
outcome of children at birth. The applied vitrification technique was the same in
all conceptions (VIT). A control group of children born after intracytoplasmic
sperm injection (ICSI) with fresh embryo transfer on day 5 was included in
order to determine whether potential differences in children's outcome could be
exclusively attributed to the vitrification procedure.
Material and Methods: A prospective longitudinal follow-up study on medical
outcome of all children born after vitrification and after ICSI at the Centre
for Reproductive Medicine of the UZ Brussel has been undertaken since March
2008. Data on pregnancy and birth were obtained through written questionnaires.
The children were examined and checked for possible major anomalies
at 2 months of age by trained clinical geneticists. Malformations were classified
according to criteria previously defined in our centre. A major malformation
causes functional impairment and/or requires surgical correction. Mean
term, birthweight, major malformations, perinatal death rate and the number of
neonatal hospitalizations were compared for both groups. Statistical analysis
included the Student's t test and the Fisher's exact test for comparing continuous
and categorical variables, respectively.
Results: Between March 2008 and November 2010, 6301 embryos were vitrified
on day 5 in 2080 ICSI cycles. Of these, 2180 embryos were thawed in 1380
cycles. 325 women presented positive HCG values resulting in 91 still ongoing
pregnancies and 99 liveborn children.
Medical outcome of these 99 children (84 singletons, 12 twins and 3 triplets)
born after VIT were compared with 402 children (305 singletons, 91 twins and
6 triplets) conceived after intracytoplasmic sperm injection (ICSI) in our centre
between March 2008 and November 2010. Mean birth weight ± standard
deviation reached 3396 ± 737 g in VIT singletons and 3241 ± 624 g in ICSI
singletons. Mean birth weight for VIT singletons was 155 g higher compared to
ICSI singletons (p = 0.057). Correcting birth weight data for sex and gestational
age through standard deviation scores showed a slight but statistically significant
difference between VIT and ICSI singletons (p = 0.047). Mean standard
deviation score ± standard deviation for the weight at birth was -0.03 ± 1.62 in
VIT singletons and -0.40 ± 1.45 in ICSI singletons. No statistically significant
differences regarding mean term, prematurity (term <37w), very prematurity
(term <32w), low birthweight (<2500g), very low birthweight (<1500g),
perinatal death rate and major malformations in singletons and multiples were
observed. One VIT boy born at 39 weeks presented a major malformation (a
hypoplastic left heart) and died at the age of 5 months. Malformation rate in
liveborn VIT children was 1/99 compared to 11/402 in ICSI children (p = 0.48).
VIT singleton neonates (19/84) were more frequently hospitalized compared to
ICSI neonates (40/305) (p = 0.039). Neonatal hospitalization was not significantly
different for VIT and ICSI multiples.
Conclusion: Neonatal outcome after vitrification of day 5 embryos is reassuring.
However, further evaluation of these preliminary data on the medical outcome
of newborn children born after transfer of vitrified embryos in a larger
and long-term follow-up study is needed.

Publication year:2011

Keywords:Neonatel outcome