2008년 미국불임학회(ASRM) P-228 significant seasonal variability in pregnancy rates in women undergoing IVF was demonstrated. (시험관 시술 시 계절적 변동성과 임신율에는 중요한 상관 관계가 있다.)

K. H. Lee, S. G. Kim, S. J. Kim, S. K. Lee, B. R. Do.
Mamapapa & baby obstetrics and Gynecology, Ulsan, Republic of Korea.

OBJECTIVE

Several studies have investigated seasonal variations during IVF-ET. Their results are contradictory, especially concerning pregnancy rates. The study's aim was to investigate the influence of seasonality in pregnancy rates following IVF-ET.

DESIGN

Retrospective study.

MATERIALS AND METHODS

We retrospectively studied 772 consecutive cycles of 732 women who underwent IVF-ET treatment over a 3-year period (2004 ~ 2006) at our institution. The seasons were defined before analyzing the data, according to the calendar definitions of the seasons in Korea, three months each, as follows: Winter: December ~ February, Spring: March ~ May, Summer: June ~ August, Autumn: September ~ November. We divided with four seasons according to the day when it picks the ovum, and we analyzed a pregnancy rate. Pregnancy rate are compared among different groups using t-test.

RESULTS

The mean±SD age of the patients (winter: 33.7±4.3; spring: 33.8±3.7; summer: 34.0 ±4.0; and autumn: 34.0± 4.1), fertilized oocytes (8.1±4.7; 7.2±4.5; 7.8±5.2; 8.5±6.0) and the embryos transferred (4.0 ± 1.0; 3.9±1.2; 3.9±1.2; 4.0±1.3) were comparable in patients by season. The 772 embryo transfers performed during the study period resulted in 371 pregnancies (48.1%), of which 310 proved to be ongoing pregnancies (40.2%). An Implantation rate of 18.6% was recorded. Average seasonal variability in pregnancy rates was demonstrated. A one-way analysis of variance showed a significant seasonal variability in pregnancy rates: winter: 44.6 (62/139) %; spring: 53.5 (92/172) %; summer: 50.2 (130/259) %; and autumn: 43.1 (87/202) %(P <0.01). Note that the highest pregnancy rates were observed during the spring and the lowest in the autumn.

CONCLUSION

This study demonstrates a significant seasonal variability in the pregnancy rates in IVF-ET. Comparing our analysis of the different seasons, the highest pregnancy rates were found in spring, despite a lower number of retrieved oocytes, fertilized oocytes and embryo transfers. Moreover, there were lower conception rates during autumn, the time period when both retrieved oocytes and fertilized oocytes are at their highest. However, the effectiveness of this study is drawn into question due to the fact that there were no proven correlations established between pregnancy rates and any of the seasonal parameters (including temperature, humidity and other environmental factors). Therefore, further studies are necessary to confirm this predictive parameter and to achieve more precise results in a larger population.