What is implantation bleeding?
After fertilisation, the egg divides as it travels along the fallopian tube for a few days and then reaches the womb. About 6-12 days after ovulation, most often around days 8-10, it attaches to the lining of the womb (endometrium). During this attachment (implantation), small blood vessels in the lining may be disturbed and a small amount of blood can pass from the vagina. This is called implantation bleeding.
Implantation bleeding does not happen in every pregnancy. Some women notice light spotting at this time, while many have none at all. Having no bleeding does not mean you are not pregnant or that something is wrong. Implantation bleeding is harmless and needs no treatment; what matters is making sure the spotting is not due to another cause.
Why is it confused with a period?
Implantation happens very close to the time a period is due. In a regular 28-day cycle, ovulation is around day 14 and implantation follows one to one and a half weeks later, just before the expected period. That is why many women read this spotting as "an early or light period". In women with irregular cycles, timing is even less helpful.
In general, these differences can be a guide:
- Amount: implantation bleeding is usually just spotting, often noticed only when wiping or on a panty liner. A period usually builds up and needs pads or tampons.
- Colour: implantation bleeding is mostly light pink or brown. Period blood is usually red from the first days.
- Duration: implantation bleeding lasts from a few hours to a day or two and stops on its own. A period usually lasts 3-7 days.
- Clots: clots are not expected with implantation bleeding; small clots can occur during a period.
- Cramps: mild pelvic tightness can occur around implantation; period cramps are often stronger.
These features are only clues. Some periods are light, and some pregnancies have heavier bleeding early on. You cannot tell whether you are pregnant from the appearance of the bleeding; a pregnancy test answers that question. For other early signs, see our article on the early signs of pregnancy.
When should you test after spotting?
Pregnancy tests measure beta-hCG, the hormone produced after the embryo implants. A test taken during or straight after the spotting may be negative because the hormone has not yet risen enough.
- Home urine test: most reliable from the first day of a missed period. Waiting a few days after the spotting and using first-morning urine lowers the chance of a false negative. If the test is negative and your period does not start, repeat it in 2-3 days.
- Blood beta-hCG: more sensitive, can detect pregnancy about 10-12 days after ovulation and gives a number. When there is bleeding in early pregnancy, your doctor may want to see how the level changes over about 48 hours.
You can work out a suitable test date from your last period with our when to take a pregnancy test tool. How beta-hCG results are interpreted is explained in our article on beta-hCG levels.
Other causes of bleeding in early pregnancy
Not every bleed after a positive test is implantation bleeding. Spotting or bleeding in the first three months is common, and in many women the pregnancy continues normally. Even so, the cause can only be found by examination and ultrasound, so any bleeding in early pregnancy should be reported to a doctor. Possible causes include:
- Changes in the cervix: in pregnancy the blood supply to the neck of the womb (cervix) increases and the tissue becomes more delicate. Light spotting after sex or a pelvic examination is often due to this. Cervical polyps or infections can also cause bleeding.
- Subchorionic haematoma: a small collection of blood between the membranes around the pregnancy sac and the wall of the womb. It is seen on ultrasound and often resolves with time, but needs follow-up.
- Threatened miscarriage: bleeding while the pregnancy is ongoing, sometimes with mild cramps. Many pregnancies with a heartbeat on ultrasound continue without problems despite bleeding. If bleeding becomes heavier, with cramps stronger than period pain or passing of tissue, a miscarriage may be happening.
- Ectopic pregnancy: the embryo implants outside the womb, most often in a fallopian tube. Light, irregular, often brown bleeding with one-sided pelvic pain is a common picture, which is why it can be confused with implantation bleeding. Untreated, it can rupture the tube and cause internal bleeding, so early diagnosis matters. See our page on ectopic pregnancy for details.
- Molar pregnancy: a rare condition caused by abnormal growth of placental tissue. It may present with bleeding, marked nausea and vomiting and higher than expected beta-hCG levels; it is diagnosed by ultrasound and tissue examination.
When there is bleeding with a positive test, the doctor usually performs a transvaginal ultrasound to check whether the pregnancy is inside the womb and may repeat the beta-hCG test. In the very early weeks the pregnancy sac may not yet be visible. In that case it is followed as a "pregnancy of unknown location", and a repeat assessment a few days later may be needed before a clear answer can be given.
Bleeding after IVF embryo transfer
Light spotting can occur in the days after embryo transfer. It may be due to contact with the cervix during transfer, vaginal progesterone medicines or implantation. On the other hand, bleeding can also start when pregnancy has not occurred. So spotting after transfer should not, on its own, be read as either a good or a bad sign.
Even if you bleed, do not stop your progesterone support or other medicines on your own; let your treatment team know and wait for the planned test date. Because the trigger injection contains hCG, early home tests can be misleading; a blood test is preferred after IVF.
Rh-negative blood group
If your blood group is Rh negative and you have bleeding in pregnancy, always tell your doctor. In some situations an anti-D injection (Rh immunoglobulin) is given to stop the mother developing antibodies against the baby's blood group. Whether it is needed is decided by your doctor, taking into account the stage of pregnancy and the cause of bleeding.
When should you see a doctor?
If you might be pregnant or have a positive test, seek care without delay, going to the emergency department if necessary, if you have:
- Heavy bleeding that soaks a pad, or bleeding with clots
- One-sided, severe or worsening pelvic pain
- Pain at the tip of the shoulder (a possible sign of internal bleeding)
- Dizziness, fainting or feeling faint, or a racing heart
- Fever or a foul-smelling discharge
- Passing of tissue
Even without these signs, tell your doctor about any bleeding with a positive test. Early assessment is advised if you have had an ectopic pregnancy before, have had surgery on your tubes, conceived with IVF or conceived with an intrauterine device (coil) in place. You should also be examined if your test is negative but your period is still late, or if you have repeated spotting between periods.
Frequently Asked Questions
How long does implantation bleeding last?
Will a test be positive straight after implantation bleeding?
Can red bleeding with clots be implantation bleeding?
Is implantation bleeding harmful to the baby?
I had spotting but my test is negative. Could I still be pregnant?
I bled after embryo transfer. Should I stop my medicines?
Sources
The information on this website is for general information only and does not replace a medical consultation.
