Implications of assisted reproductive technologies on term singleton birth weight: an analysis of 25,777 children in the national assisted reproduction registry of Japan.
OBJECTIVE
To evaluate the implications of assisted reproductive technologies (ART) on neonatal birth weight.


METHODS
A retrospective study using analysis of covariance and multiple logistic regression analysis of the Japanese ART registry.


METHODS
Japanese institutions providing ART treatment.


METHODS
A total of 25,777 singleton neonates reaching term gestation following ART during the years 2007-2008, with 11,374 achieved through fresh embryo transfers (fresh ET) and 14,403 achieved through frozen-thawed embryo transfers (FET).


METHODS
None.


METHODS
Birth weight.


RESULTS
The mean birth weight after FET was significantly higher compared with fresh ET and all Japanese births (3,100.7 ± 387.2 g, 3,009.8 ± 376.8 g, and 3,059.6 ± 369.6 g, respectively). The risk for low birth weight in FET was significantly lower compared with fresh ET. In fresh ET, ovarian stimulations were associated with about twofold risk of low birth weight compared with natural cycle. Regarding to the duration of embryonic culture, the risks resulting from a shorter culturing time were significantly higher compared with a longer culturing time in fresh ET.


CONCLUSIONS
The best method of embryo transfer for fetal growth was FET after extended culturing until blastocyst stage. However, further investigations should be performed to understand the safety of ART treatment.
Division of Reproductive Medicine, National Center for Child Health and Development, Tokyo, Japan. nakadiam@gmail.com
Akira
A
Nakashima
Ryuichiro
R
Araki
Hirohiko
H
Tani
Osamu
O
Ishihara
Akira
A
Kuwahara
Minoru
M
Irahara
Yasunori
Y
Yoshimura
Takeshi
T
Kuramoto
Hidekazu
H
Saito
Aritoshi
A
Nakaza
Tetsuro
T
Sakumoto
D001724:Birth Weight; D005260:Female; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007246:Infertility / Q000453:epidemiology* / Q000628:therapy*; D007564:Japan / Q000453:epidemiology; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D015995:Prevalence; D012042:Registries; D027724:Reproductive Techniques, Assisted / Q000706:statistics & numerical data*; D012307:Risk Factors