Implantation symptoms explained

If you're hoping to have a baby, implantation is a big step in the process. You have an egg fertilized, it's growing, and it's burrowing into your uterus where it'll continue to develop. Implantation even signals your body to produce all those baby-supporting hormones.

You can think of it as the official start of your pregnancy! Read on to find out more about the process.

What is implantation?

Implantation happens when the fertilized egg (called an embryo at this point) moves down the fallopian tube, enters the uterine cavity, and starts to burrow in the lining of your uterus. During the trip, it continues dividing into more and more cells until it's composed of a mass of about 200 to 300 cells. At this point the embryo is called a blastocyst, and it attaches to the lining of your uterus, where the cells will divide further into your baby and the placenta. (If it doesn't implant, you'll have a menstrual period.)

When implantation does happen, your body starts producing the hormone hCG, which will result in a positive pregnancy test. During the first 30 days after implantation, hCG concentration doubles every 29 to 53 hours.

When does implantation occur?

According to the American College of Obstetricians and Gynecologists,Opens a new window implantation symptoms can occur a week or two after ovulation, as the fertilized egg implants in the lining of the uterus.

The thing is, we don't always know when ovulation occurs. If you have an average 28-day cycle, ovulation (when one of your ovaries releases an egg) usually happens about two weeks after the beginning of your last period. But women's cycles vary from 21 to 35 days, making it difficult to pinpoint ovulation and implantation unless you're being monitored by a fertility doctor.

"Getting pregnant can be tricky, and timing is everything!" says Courtney Marsh, M.D., director of Obstetrics and Gynecology and division director of Reproductive Endocrinology at the University of Kansas Health System.

How long does implantation take?

It takes about three to four days for the egg to be transported through the fallopian tube to the uterus. It's helped along by finger-like, hairy projections within the tubes as well as muscular contractions. Once the embryo reaches the uterine cavity, implantation takes only a day or two, three at the most.

Implantation symptoms

Implantation symptoms can be very subtle. In fact, you may not notice any at all.

"Though some may notice implantation bleeding, most women will be completely unaware that implantation is occurring," says Sasha Hakman, M.D., an ob-gyn and reproductive endocrinology and infertility specialist in Phoenix.

Making it even harder to detect, some implantation signs can mimic signs of PMS or ovulation symptoms. And a few are also early pregnancy signs.

If you do have implantation symptoms, they may be:

• Light cramping. Implantation cramps are similar to menstrual cramps but milder. You may feel them in the middle of your lower abdomen and/or lower back.
• Slight bleeding. Implantation bleeding happens as the embryo embeds into the lining of the uterus, which is filled with blood vessels and tissue. Because of the timing, you might think you're getting your period. But the bleeding will stay light, last only a day or two, and be light pink or brown, not red like your period.
• Nausea and/or bloating
• Breast tenderness
• Lower back pain
• Mood swings
• Headaches

How soon after implantation can I take a pregnancy test?

A pregnancy test relies on the presence of human chorionic gonadotropin (hCG) in your urine. Your body produces small amounts of this hormone as early as six days after conception. When your body produces enough hCG to appear in your bloodstream and urine, it's possible to get a positive result on a test. According to the U.S. Food & Drug Administration (FDA) if you have a 28-day menstrual cycle, you can detect hCG in your urine 12 to 15 days after ovulation.

Some pregnancy test manufacturers say they provide results even before your period is due, but for accuracy it's best to wait until the first day of your missed period. That's when you would be 4 weeks pregnant, and there's more hCG in your body. Even then might not be long enough to get an accurate result, though.

"Because many women have irregular periods, and women may miscalculate when their period is due, 10 to 20 pregnant women out of every 100 will not detect their pregnancy on the first day of their missed period," explains the FDA.

If you think you've experienced implantation and want definitive results, wait a couple of weeks and take the test the morning of your expected period. If you're just too eager to wait, you can take it earlier and then repeat it in a week or so if you get a negative pregnancy test.

Also, says Marsh, "If you notice that your period is irregular or more than a week late, check a pregnancy test. If it's negative, it may be best to check with a provider to see if you're ovulating regularly."

Implantation complications

If the egg implants someplace other than your uterus – such as in a fallopian tube (most commonly), a previous c-section scar, your cervix, your ovary, or your abdominal cavity – you have an ectopic pregnancy. An ectopic pregnancy is a medical emergency, so it's important to know the signs and get help right away.

Call 911 right away if you have signs of a ruptured fallopian tube, such as a weak and racing pulse, dizziness, fainting, and pale, clammy skin.

If you have other signs of an ectopic pregnancy, call your provider immediately (and go to the ER if they're not available). These signs include:

• Abdominal or pelvic pain or tenderness. It may be mild and intermittent at first or it can be sudden and severe.
• Vaginal spotting that may be heavy or light, continuous or intermittent.
• Shoulder pain, especially when you lie down. This is caused by internal bleeding and it's a hallmark sign of an ectopic pregnancy.

In some instances, failed implantation can occur. Recurrent implantation failure can be a problem for some people undergoing IVF.