Implantation is one of the most dramatic biological events of your entire pregnancy — fertilization being the first. You may not even notice that implantation is happening, although some women experience period-like cramping and a little spotting.
Either way, implantation silently marks the making of an embryo even before you know for sure that you're expecting.
What is implantation during pregnancy?
Implantation is when an embryo burrows deep into the lining of the uterus, where it can then begin to grow. Implantation happens after fertilization, which is when sperm meets egg. Fertilization takes place in the fallopian tube, according to the American College of Obstetricians and Gynecologists (ACOG).[1] Then, as the embryo begins to divide, it travels down the fallopian tube before coming to implant in the lining of the uterus.
From a medical perspective, successful implantation is the true start of pregnancy, says Tarun Jain, M.D., a reproductive endocrinologist, fertility specialist and associate professor at Feinberg School of Medicine and a member of the What To Expect Medical Review Board.
Once the embryo is implanted, it starts releasing hormones that prepare your body for baby, turning off your period, building up the placenta and possibly making you feel crampy and tired.
When does implantation occur?
Implantation occurs about eight to nine days after fertilization, though it can happen as early as six days and as late as 12 days after ovulation.
Put another way: “If a woman has a regular 28-day menstrual cycle, ovulation typically occurs around day 14 of the cycle, and implantation may occur between days 20 to 26,” Dr. Jain says.
What are the signs and symptoms of implantation?
Some women notice signs of implantation, while others do not. “Not experiencing signs of implantation does not necessarily mean that you are not pregnant,” Dr. Jain says. “Many women do not experience any symptoms of implantation, and still go on to have healthy pregnancies.”
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That said, signs of implantation can include:
Light bleeding
The difference between implantation symptoms and your period can be confusing, especially because in both instances, the blood is shed from the uterine lining. “The light bleeding that occurs during implantation is caused by the mild erosion of the uterine lining as the embryo implants.” Dr. Jain says.
While most women don't experience implantation bleeding, some will, with up to 25 percent of them experiencing light, spotty blood, according to the Cleveland Clinic.[2] This blood usually starts out pink and turns brown, and unlike your period, it won't flow or contain clots. It should stop within a day or two.
Abdominal cramps
Many women don't have any symptoms of implantation, but the subsequent hormonal shifts can cause cramps. Implantation cramps should last only a day or so at most, and you'll probably notice them around the time your period is due.
You might think the cramps are caused by the embryo actually attaching to your uterine lining, but that’s not quite true, Dr. Jain explains. “The cramping that you feel is caused by the stretching of the uterine muscles as the embryo implants.”
While abdominal cramps are never fun, minor implantation cramps in early pregnancy are very common and shouldn't be as uncomfortable as those you might get before and during your period.
Instead, you might feel a prickly or tingling sensation in your abdomen, as well as light pressure. Check in with your practitioner if you feel intense pain.
Other possible signs
Implantation isn't exactly painful, but very early pregnancy — no matter how joyful — can make you feel sick.
While implantation itself is not to blame for the symptoms below, the cascade of hormonal changes helping your body launch a new life can leave you feeling temporarily weak and woozy.
Besides cramping and light bleeding, some women report:
- Swollen breasts
- Low energy
- Headaches
What is an implantation dip?
During the second half of the menstrual cycle, a woman's temperature starts to rise and goes up about 1 degree Fahrenheit at the time of fertilization, where it remains elevated throughout her pregnancy.
If your temperature drops back down, it could mean that your period is on its way, implantation didn't occur and you're not pregnant.
When should you take a pregnancy test?
Implantation is an important but easy-to-miss event. Because it can cause light spotting, some women mistake it for their menstrual cycle. If your period doesn't come and you are wondering whether or not you are actually pregnant, take a home pregnancy test or see your practitioner for confirmation.
Although you'll probably be understandably anxious to take a test as soon as possible, your best bet is to wait until about 19 days after fertilization.
Human chorionic gonadotropin (hCG) production begins when the embryo implants in your uterus, and by 19 days after fertilization, hCG levels have built up enough to be detectable in your urine.
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