When does implantation occur? Timing and symptoms

If you might be pregnant and you have bleeding or pain, the timing in this guide cannot tell you what is causing it. The NHS treats bleeding in pregnancy as an emergency when it comes with severe abdominal pain, pain in the shoulder, or feeling sick, faint or dizzy, and when it is heavy enough to soak a period pad soon after you put it on (NHS, "Vaginal bleeding in pregnancy", 2026). In the UK, call the emergency number or go to A&E, the hospital emergency department; in the US, call the emergency number or go to the nearest emergency room. The box above shows the emergency and urgent numbers for where you are, and get help now lists the other symptoms that need checking straight away.

When does implantation occur?

Implantation is when the early embryo attaches to the lining of the uterus, and when it occurs has been measured directly in one study. Wilcox, Baird and Weinberg collected daily urine samples for up to six months from 221 women who had stopped contraception to conceive. They found the day of ovulation from hormone measurements and took implantation to be the day the pregnancy hormone hCG first appeared in urine. Among the 141 pregnancies that lasted at least six weeks, hCG first appeared 6 to 12 days after ovulation, and in 118 of them, 84 in 100, it appeared on day 8, 9 or 10 (Wilcox et al., 1999). The authors conclude that in most successful pregnancies implantation happens 8 to 10 days after ovulation.

When implantation happens on a calendar depends on when you ovulate. ACOG's guidance on due dates assumes ovulation on day 14 of a 28-day cycle (ACOG Committee Opinion 700, 2017). On that cycle, 6 to 12 days after ovulation is cycle day 20 to 26, and the most common days, 8 to 10, are cycle days 22 to 24, all before a period would be due on day 29. That is our arithmetic, and it shifts with the length of your cycle. The ovulation calculator estimates the day you ovulate, and the pregnancy test calculator, which doubles as an implantation calculator, works out the implantation window from it.

When does implantation happen, according to other health bodies? They give rounder figures. The US Office on Women's Health says implantation usually happens about 10 days after conception, and that in up to 10 in 100 women it does not happen until after the first day of a missed period (Office on Women's Health, 2025). The NHS says hCG starts to be produced around 6 days after fertilization (NHS, "Doing a pregnancy test", 2022). The figures count from different starting points, ovulation, conception and fertilization, and only the Wilcox study reports days it measured.

How many days after ovulation, conception or sex

After ovulation

How many days after ovulation does implantation occur? In the Wilcox study, 6 to 12, most often 8 to 10 (Wilcox et al., 1999). How long after ovulation does implantation occur, and how many days after ovulation is implantation? The same 6 to 12 days for the pregnancies in that study that continued, and most often 8 to 10.

After conception

How long after conception does implantation occur? The Office on Women's Health says about 10 days (Office on Women's Health, 2025), and the NHS dates the first hCG to around 6 days after fertilization (NHS, "Doing a pregnancy test", 2022). The sources cited here do not give the gap between ovulation and fertilization, so the counts from conception and from ovulation cannot be lined up exactly. A review of how implantation works describes its first stage as beginning about 2 to 4 days after the early embryo, at the stage called a morula, enters the cavity of the uterus (Kim and Kim, 2017).

After sex

How long after sex does implantation occur? Sex has to come before ovulation or on the day: in a study of 221 women, Wilcox, Weinberg and Baird found conception only from intercourse during the six days ending on the day of ovulation (Wilcox et al., 1995). Adding the 6 to 12 days from ovulation to implantation, implantation would fall roughly 6 to 17 days after the sex that led to a pregnancy. That is our arithmetic on two studies, not a figure either of them gives. How many days after sex does implantation occur? A range, not a day.

What implantation is

What is implantation? It is the process by which the early embryo, at the stage called a blastocyst, attaches to the lining of the uterus and then grows into it. As it does, the blastocyst separates into the cells that become the embryo and the outer cells that become the placenta (Kim and Kim, 2017). MedlinePlus says the placenta starts making hCG after the fertilized egg attaches to the inside wall of the uterus (MedlinePlus, "Pregnancy Test", 2026), which is why implantation has to come before a positive test. hCG levels covers the hormone.

The stages of implantation

Kim and Kim's review describes three stages of implantation (Kim and Kim, 2017):

1. Apposition: the blastocyst makes contact with the implantation site on the lining of the uterus.
2. Adhesion: cells on its outer layer, the trophoblast, attach to the surface of the lining.
3. Invasion: trophoblast cells cross the membrane beneath that surface and move into the tissue below it.

The 4 stages of implantation are searched for often, but the review cited here describes three, and none of the other sources on this page gives a four-stage version.

Implantation symptoms: what the evidence shows

Implantation symptoms and signs of implantation are listed on many websites, usually as spotting, cramps, sore breasts, nausea, mood changes and a dip in temperature. The health bodies cited here describe one: light bleeding. The NHS lists a bleed similar to a very light period, with some spotting or only a little blood, around the time a period is due, and calls it implantation bleeding (NHS, "Signs and symptoms that might mean you're pregnant", 2026). ACOG says light bleeding or spotting can occur 1 to 2 weeks after fertilization, when the fertilized egg implants in the lining of the uterus (ACOG, "Bleeding During Pregnancy", 2021). Neither gives a way to tell it from other bleeding, and implantation bleeding, sometimes searched as implantation spotting, covers what is known about it.

The other symptoms of implantation on those lists appear on the NHS's list of early signs of pregnancy, which it says usually start at around 4 to 6 weeks (NHS, "Signs and symptoms that might mean you're pregnant", 2026). None of the NHS, ACOG, FDA, MedlinePlus or Office on Women's Health pages cited here attributes nausea, breast changes or mood changes to implantation itself, and none of the sources cited here describes an implantation dip in body temperature. Early pregnancy symptoms sets out the full list of signs and when they tend to start.

Symptoms before implantation

Fertilization symptoms before implantation are a common search. Before implantation the pregnancy hormone hCG is not yet being made: the FDA says it appears shortly after the embryo attaches to the wall of the uterus (FDA, 2019), and the NHS says it starts to be produced around 6 days after fertilization (NHS, "Doing a pregnancy test", 2022). None of the sources cited here describes symptoms caused by fertilization.

Implantation cramps

Implantation cramps, or implantation cramping, are searched for almost as often as implantation symptoms, but no NHS, ACOG, FDA, MedlinePlus or Office on Women's Health page cited here describes cramping caused by implantation. What has been measured is cramping in early pregnancy in general. In a US study that followed couples from before conception, 341 women with a positive home test recorded their symptoms every day from 2 to 7 weeks after conception, and 85 in 100 recorded lower abdominal cramping at some point (Sapra et al., 2016). The study reports cramping over those weeks, not on the day of implantation, so it cannot show whether any of it came from implantation.

Can you feel implantation?

What does implantation feel like, what do implantation cramps feel like, and what does implantation cramping feel like? The sources cited here do not say. The study that timed implantation recorded a hormone appearing in urine, not sensations (Wilcox et al., 1999), and implantation pain as a separate symptom is not described by any of the health bodies cited here.

Implantation cramps vs period cramps

Implantation cramps vs period cramps cannot be told apart from the sources cited here, and the timing makes it harder: on a 28-day cycle, implantation falls a few days before a period would be due. Cramping in early pregnancy compares period cramps with early pregnancy cramps using what the NHS and Mayo Clinic say. Pain is also a reason to get advice. The NHS advises calling your maternity unit straight away if stomach pain in pregnancy comes with vaginal bleeding or spotting, and says the symptoms of an ectopic pregnancy typically appear between 4 and 12 weeks and can include tummy pain and bleeding, pain in the tip of the shoulder and discomfort when peeing or pooing (NHS, "Stomach pain in pregnancy", 2024).

From implantation to a positive test

How long after implantation does hCG rise? MedlinePlus says the placenta starts making hCG after the fertilized egg attaches, and that levels then keep rising for ten weeks, almost doubling every three days (MedlinePlus, "Pregnancy Test", 2026). The FDA says that with a 28-day cycle, hCG can be detected in urine 12 to 15 days after ovulation (FDA, 2019).

So how soon after implantation can I test, and how long after implantation can you test? Set beside the Wilcox figures of 6 to 12 days for implantation, the FDA's 12 to 15 days puts a positive urine test a few days after implantation rather than on the same day. That is our reading of two separate sources; neither gives a number of days after implantation, so how many days after implantation can you test, or how long after implantation can I test, has no measured answer. The NHS says most tests can be done from the first day of a missed period, and that some very sensitive tests can be used before it (NHS, "Doing a pregnancy test", 2022). Because implantation can come late, the Office on Women's Health says a home test can be accurate as soon as 1 day after a missed period for some women but not for others (Office on Women's Health, 2025).

How soon can you take a pregnancy test compares the UK and US advice on timing, and the pregnancy test calculator gives the earliest day a home test is reliable from your dates.

When to get help

Any bleeding in pregnancy is worth reporting: ACOG advises contacting your ob-gyn if you have any bleeding at any time during pregnancy, and says vaginal bleeding is sometimes the only sign of an ectopic pregnancy (ACOG, "Bleeding During Pregnancy", 2021). The NHS advises getting urgent help for light bleeding or spotting even with no pain or mild tummy pain, and gives the emergency signs in the paragraph at the top of this guide (NHS, "Vaginal bleeding in pregnancy", 2026). Bleeding in early pregnancy sets out who to contact where you are.

This guide is information, not a diagnosis or a recommendation of treatment, and it is no substitute for your own clinician. See the medical disclaimer.