What is Implantation Bleeding and When Does It Occur?

When a fertilized egg moves down the fallopian tubes and into the uterus, anywhere from six to 12 days after conception, it secures itself to the uterine wall in what’s known as implantation. This process can affect small blood vessels in the walls of the uterus, causing bleeding that appears externally as small amounts of pink, reddish, brown or black discharge.

Implantation bleeding is common, occurring in approximately 25 percent of pregnancies. For many women, this is the first sign that they’re pregnant. However, it can be hard to know whether what you’re experiencing is implantation bleeding or just a light period.

How to Distinguish Implantation Bleeding from a Period

There are certain characteristics to look for and some steps you can take to determine the cause of your spotting or light bleeding, including:

  • Menstrual bleeding tends to start heavy and taper off over 3-5 days, whereas implantation bleeding is light and lasts 24-48 hours.
  • Menstrual blood is typically bright red for at least some of the days of your period. Implantation bleeding is more often brown, pink or black.
  • A regular period may be accompanied by intense cramping. With implantation, there’s little or no cramping.
  • Implantation bleeding typically occurs before you’d normally expect your period to start.
  • If it has been more than two weeks since you had sex, it’s unlikely that you’re experiencing implantation bleeding.
  • Implantation bleeding may be accompanied by symptoms like nausea, headache, breast tenderness, and low backache.
  • If you suspect you might be pregnant, you can wait a few days and then take a pregnancy test.

When to Contact Your Doctor

Vaginal bleeding can be caused by a variety of things, including a pelvic exam, sex or an infection. In many cases, it turns out to be of no concern. However, unexpected bleeding is nevertheless a good reason to talk with your doctor, who may want to perform a vaginal ultrasound.

In particular, you should seek prompt medical attention if you experience any of the following symptoms which can indicate an ectopic pregnancy or miscarriage:

  • Bleeding bright red blood
  • Passing clots
  • Significant cramping
  • Feeling dizzy or especially tired following a positive pregnancy test

If these occur at night, you can call your doctor’s office and speak with the on-call physician. Or, if you feel the situation is urgent, you can go to the emergency room for evaluation.


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