Implantation: definition and meaning
Implantation is the moment a fertilized egg, by then a tiny ball of cells called a blastocyst, attaches to and burrows into the lining of the uterus. It usually happens 6 to 10 days after ovulation, most often around day 8 or 9. After implantation the body starts making hCG, the hormone pregnancy tests detect.
What happens during implantation
After an egg is fertilized in a fallopian tube, it divides as it travels toward the uterus for several days. By the time it arrives it is a blastocyst. It then attaches to the thick, nourishing endometrial lining that progesterone prepared during the luteal phase, and gradually embeds into it.
- Day 0: ovulation, the egg is released
- Within about 24 hours: fertilization, if sperm are present
- Days 5 to 6: the blastocyst reaches the uterus
- Days 6 to 10: implantation, most often around day 8 to 9
- A few days later: hCG is high enough for a sensitive home test
Signs of implantation
Most people feel nothing at all. Some notice light implantation bleeding or mild cramping around the time their period would be due, but these signs are unreliable because the same things happen before a normal period. The only way to know is a pregnancy test, ideally from the first day of a missed period.
Want to estimate your own window? Our implantation calculator works it out from your ovulation day or last period.
Implantation and mood
The days around implantation fall in the late luteal phase, when PMS symptoms like tiredness, sore breasts and mood dips are common anyway. Feeling emotional during the two-week wait is normal, and it is not a sign either way.
Frequently asked questions
How long does implantation take?
The process of attaching and embedding takes a few days, starting about 6 to 10 days after ovulation.
Can you feel implantation?
Most people can't. Light cramps or spotting are possible, but they look just like early PMS, so a test is the only reliable answer.
Sources
- NHS: Signs and symptoms of pregnancy
- Wilcox AJ et al. Timing of sexual intercourse in relation to ovulation. NEJM (1995)
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
Implantation calculator: when does implantation happen?Free implantation calculator: see the days implantation would most likely happen this cycle, what implantation bleeding looks like, and when to test.What does implantation bleeding look like?What does implantation bleeding look like? Light pink or brown spotting, no clots, lasting hours to 2 days. How it differs from a period and when to test.
Human chorionic gonadotropin (hCG): definitionhCG is the hormone made after implantation that pregnancy tests detect. How fast it rises, what beta hCG numbers mean, and when a test can turn positive.
Two-week wait (TWW): what it meansThe two-week wait is the time between ovulation and a reliable pregnancy test. What happens in your body, when to test, and kind ways to cope with the wait.When to take a pregnancy test: find your most accurate dayWhen to take a pregnancy test: enter your last period and cycle length to see the earliest testing day and the day a result is most reliable.