Vitrified-warmed embryo transfer is associated with mean higher singleton birth weight compared to fresh embryo transfer.
OBJECTIVE
To test for differences in birth weight between singletons born after IVF with fresh embryo transfer vs. vitrified-warmed 2PN embryo transfer (vitrification protocol).


METHODS
Retrospective analysis of 464 singleton live births after IVF or ICSI during a 12 year period.


METHODS
University hospital.


METHODS
Fresh embryo transfer, vitrified-warmed 2PN embryo transfer (vitrification protocol).


METHODS
Birth weight standardized as a z-score, adjusting for gestational week at delivery and fetal sex. As a reference, birth weight means from regular deliveries from the same hospital were used. Multivariate regression analysis was used to investigate the relationship between the dependent variable z-score (fetal birth weight) and the independent predictor variables maternal age, weight, height, body mass index, RDS prophylaxis, transfer protocol, number of embryos transferred, indication for IVF treatment and sperm quality.


RESULTS
The mean z-score was significantly lower after fresh transfer (-0.11±92) as compared to vitrification transfer (0.72±83) (p<0.001). Multivariate regression analysis indicated that only maternal height and maternal body mass index, but not type of cryopreservation protocol, was a significant predictor of birth weight.


CONCLUSIONS
In this analysis focusing on 2PN oocytes, vitrified-warmed embryo transfer is associated with mean higher birth weight compared to fresh embryo transfer. Maternal height and body mass index are significant confounders of fetal birth weight and need to be taken into account when studying birth weight differences between ART protocols.
Department of Obstetrics and Gynaecology, Westpfalz-Klinikum, Kaiserslautern Hellmut-Hartert-Str. 1, 67655 Kaiserslautern, Germany. Electronic address: danielbeyer@t-online.de.
Daniel Alexander
DA
Beyer
Department of Gynecological Endocrinology and Reproductive Medicine, University Hospital of Schleswig-Holstein, Campus Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany.
Georg
G
Griesinger
D000328:Adult; D001724:Birth Weight; D015992:Body Mass Index; D015331:Cohort Studies; D015925:Cryopreservation; D004624:Embryo Transfer / Q000009:adverse effects*; D005191:Family Characteristics; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects; D047109:Fetal Development; D005858:Germany; D006785:Hospitals, University; D006801:Humans; D007231:Infant, Newborn; D007247:Infertility, Female / Q000628:therapy*; D007248:Infertility, Male; D008297:Male; D015999:Multivariate Analysis; D011247:Pregnancy; D012189:Retrospective Studies; D020554:Sperm Injections, Intracytoplasmic / Q000009:adverse effects; D058989:Vitrification
ART; IVF/ICSI; Perinatal outcome; Vitrification