How long does conception take following intercourse? The answer to this question depends almost entirely upon what point the woman is in her monthly cycle. If intercourse occurs when the woman isn't ovulating or close to ovulating, conception won't occur at all, but if she has just ovulated, is ovulating, or is about to ovulate, conception can occur anywhere from almost immediately after ejaculation to a full three days later.
Ovulation is the process by which an egg is released from a woman's ovary and sent down the fallopian tube toward the uterus. At the same time hormonal shifts cause the lining of the uterus to thicken, preparing it to support a fertilized egg. The egg can survive for about 24 hours in the fallopian tube, and it's during this time that it's ripe to be fertilized by sperm. Most women begin ovulating approximately 14 days after the start of their last period.
Sperm can breach the cervix less than 90 seconds after ejaculation, and can be found in the fallopian tubes as soon as five minutes after ejaculation. If the woman has already ovulated, and there is a viable egg waiting in one of the fallopian tubes, conception occurs as soon as a sperm fertilizes the egg. If ovulation occurs before intercourse, a healthy egg can survive for approximately 12 to 24 hours in the fallopian tube waiting to be fertilized. If fertilization does not occur in that time period, the unfertilized egg continues its journey to the uterus, where it is absorbed by the uterine lining, and then flushed out of the body during the woman's next period about 12 to 16 days after ovulation. If ejaculation occurs before ovulation, sperm can survive in the fallopian tubes for up to two to three days, waiting to fertilize the coming egg.
After the sperm has fertilized the egg, the cells of the fertilized egg, or zygote, begin to multiply. The zygote also travels the remaining length of the fallopian tube to the uterus, a process that can take up to four days after ovulation, and then implants into the uterine lining, which can occur up to a week after ovulation.