It is normal to get pregnant after having sex only once together. This is also a good indication that the time of sexual intercourse coincides with the woman’s ovulation period, her fallopian tubes are open and her eggs are mature. The man successfully ejaculated in the woman’s vagina without a condom, and his sperm was of good vitality and quality. The sperm and the egg meet successfully in the fallopian tube to form a fertilized egg, which then successfully implants in the well-developed endometrium of the uterus. That is why this leads to pregnancy in one sitting together.