Implantation—the process of the egg implanting in the uterine wall—is the part of the conception process that feels like the true beginning of pregnancy. Even though your gynecologist considers the first day of your pregnancy the first day of your last menstrual period, your pregnancy isn’t really “real” until the embryo has implanted in the uterine wall. But when, exactly, does implantation occur? Is it right after you have sex? Days, hours, or weeks later?
Although women who track their cycles can often detect the date of ovulation, there is no way to tell exactly when or if an egg implants (wouldn’t that be nice?!). Implantation most often occurs nine days after ovulation, but it can sometimes happen earlier or later than that. To understand why it takes so long, let’s review the process of conception, day by day.
About five days before ovulation marks the beginning of your fertile window. Because of the lifespan of sperm, sex up to five days before ovulation can result in conception.
Anywhere from three days to one day before ovulation, levels of luteinizing hormone will surge, sending a message to your ovaries that it’s time to release an egg. You can use an ovulation test to detect the LH surge.
During ovulation, an egg is released from the ovary into the fallopian tube, where it begins its journey to the uterus. As soon as the egg is released, the clock starts ticking: a sperm must find and fertilize the egg within 24 hours in order for conception to occur. If a sperm manages to find and penetrate an egg during its journey down the fallopian tube, the egg changes instantaneously to prevent any other sperm from entering.
During fertilization, the genetic material in the sperm and egg combine to create a new cell—called a blastocyst. The blastocyst begins to divide rapidly as it continues traveling down the fallopian tube towards the uterus. This journey takes about three days.
After the blastocyst reaches reaches the uterus, it can take another few days to implant itself in the uterine wall. Around 30 percent of women experience light bleeding around this time, but there is no evidence that implantation bleeding is an actual phenomenon. This bleeding, if it occurs, can last from several hours to a couple days. Most of the time, implantation occurs about nine days after ovulation, but it can occur as early as seven days or as late as 12 days after ovulation. Once implantation is complete, the cervix becomes closed with a mucus plug.
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