Background: Human chorionic gonadotropin (hCG) is synthesized by trophoblast cells and play a critical effect in early pregnancy. The serum hCG concentration is significantly higher in early gestation period achieved through in vitro maturation (IVM) than that by traditional IVF. Since IVM does not involve ovarian hyperstimulation, we wonder whether the number of oocyte retrieved affect the hCG concentration in early pregnancy achieved by IVM. Methods: The retrospective analysis involved 51 women who delivered singletons were analyzed. The number of oocyte retrieved and the maternal hCG concentration were collected and analyzed. Results: 51 women had delivered singletons through IVM. The mean number of oocytes retrieved was 16.78 \pm 11.23, and the hCG concentration was 614.47 \pm 445.50 IU/L and 10930.20 \pm 7223.17 IU/L at day 14 and 21, respectively. After confounding factors adjusted, the concentration of serum hCG at day 14 and 21 associated significantly with the number of oocyte retrieved. The result of crude linear regression analysis exhibited a positive relationship between the number of oocyte retrieved and the hCG concentration in early gestation. Conclusions: Our results suggested that the number of oocyte retrieved associated positively with the serum hCG level in female with early pregnancies that underwent IVM.