When a man ejaculates and then reinserts his penis into the vagina, the possibility of pregnancy cannot be ruled out in the absence of contraceptive measures. Whether you ejaculate in vitro and then re-insert it into the female vagina, or wear a condom and then remove it after ejaculation and then re-insert it, there may be residual semen and secretions on the penis, and residual semen in the vas deferens after ejaculation, which can be carried into the female vagina with the insertion, leading to pregnancy. Therefore, it is best not to insert without contraception after ejaculation if there is no plan to become pregnant. If you are unsure, you can test for pregnancy with a pregnancy test 10 days after intercourse.