Updated July 30, 2015.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Spotting when you’re trying to conceive can strike fear in your heart. Is this bad? Could it be good? Is this implantation spotting? Or the start of my period?

If you’re having fertility treatments – especially IUI or IVF – your odds of experiencing spotting are higher.

There are many possible reasons for abnormal vaginal bleeding or spotting. Keep reading to learn more about implantation spotting, spotting and early miscarriage, and spotting that has nothing to do with early pregnancy.

Implantation Spotting: A Possible Early Pregnancy Sign

Light spotting that occurs between ovulation and your expected period is sometimes referred to as “implantation spotting.”

The theory most commonly repeated online is that when an embryo implants itself into the uterine lining, the lining in that area sheds just slightly, leading to what you later see as light spotting.

There is no proof that is what’s actually occurring. It’s also unlikely. (Consider how very tiny an embryo is, and how very tiny any lining in that area may be, and you’ll see how this theory is far fetched.)

However, it could be that the embryo implanting itself into the lining does trigger a hormonal reaction that leads to very light spotting.

Spotting or vaginal bleeding in early pregnancy isn’t uncommon – it happens anywhere between 15 and 25% of the time.

Women receiving fertility treatments may be more likely to spot. One study found that during an IVF cycle, early pregnancy bleeding occurred even more often, anywhere from 29 to 36% of the time.

So, is spotting a good sign? Could it signal an early pregnancy?

That’s not clear. One study found that women taking a particular form of progesterone were more likely to experience spotting than those taking another form. While spotting was more common in one group, the pregnancy rates were similar.

In other words, spotting was neither a good nor bad sign in this study.

Spotting as the Start of an Early Miscarriage

If the spotting occurs after a positive pregnancy test, you might worry that the spotting is the start of an early miscarriage.

As stated above, spotting during early pregnancy isn’t uncommon. The good news is that spotting after a positive pregnancy test doesn’t mean you’re miscarrying.

About 50% of women who have vaginal bleeding during the first three months of pregnancy will continue their pregnancy.

I realize that 50% doesn’t sounds like great odds, but it’s clear that spotting doesn’t absolutely mean you will miscarry. There’s a good chance things will be fine.

Personally, I have had spotting during a healthy pregnancy, a healthy pregnancy with no spotting, and spotting that led to miscarriage. I couldn’t tell you the difference between those three experiences.

Don’t drive yourself crazy trying to determine if your spotting is the “bad” kind or the “normal” kind.

Make sure to call your doctor if you have any sort of vaginal bleeding after getting a positive pregnancy test. They may want to run some blood work, order an ultrasound, or prescribe progesterone support (if you’re not already taking it.)

If you don’t have a history of infertility or miscarriage, your doctor may do nothing and suggest relaxation. If things get worse, though – or you begin to experience cramping or pain – call your doctor again.

Other Reasons for Abnormal Vaginal Bleeding

Spotting can occur for reasons besides early pregnancy. A few possible causes include:

• Hormonal imbalance (Spotting may occur more often in premenopausal women, for example. Thyroid problems and birth control medications can also lead to spotting between cycles.)
• Fibroids or polyps
• Side effects of fertility drugs (Many fertility drugs, including Clomid, list spotting as a possible side effect.)
• Progesterone suppositories
• Gynecological procedures (Like a pap smear.)
• IUI or IVF procedures
• Transvaginal ultrasound (The wand can bump into the cervix, which may lead to light spotting. Also, if you’re taking fertility drugs or progesterone, the area down there is more sensitive, which makes spotting more likely.)
• Sexual intercourse (If the cervix gets hit, it can lead to light spotting in some cases. This may be more likely if you’re taking fertility drugs.)

When to Worry

Occasional spotting between periods is nothing to worry about. However, there are times you should call the doctor.

If you frequently experience spotting between periods or before your period starts. Spotting for two or more days before your period actually starts is associated with endometriosis.

Spotting can also be a symptom of an infection, a hormonal imbalance, fibroids, and, in rare cases, some cancers. Get it checked out if you frequently spot between cycles.

You’re pregnant and experience heavy bleeding. If you start to have a flow that is more similar to your period, or the spotting transitions to a heavier flow, you should contact your doctor.

If the bleeding is abnormally heavy, contact your doctor immediately or go to your nearest emergency room.

The spotting or bleeding is accompanied by pelvic pain or cramps. Mild cramps or general achiness can be normal during early pregnancy, as well as during your period. Really bad cramps are not normal.

If you’re pregnant, spotting, and having even mild cramps, call your doctor. She may simply reassure you that what you’re experiencing is normal, or choose to run some blood work or an ultrasound. But it’s better to call than assume everything is fine.  

If you’re experiencing severe pain, go to the nearest emergency room and contact your doctor immediately.

Vaginal bleeding with severe pain could indicate an ectopic pregnancy or, if you’ve taken fertility drugs, a complication of ovarian hyperstimulation syndrome (OHSS). It can also be a sign of acute PID. Get medical attention ASAP!

More on worrisome symptoms:

• Quiz: Do You Have Infertility Symptoms?
• 8 Embarrassing Secrets You Must Tell Your OB/GYN
• 6 Signs Your Period Cramps Aren’t Normal
• What Is a Normal Period

More on early pregnancy:

• Quiz: Are You Pregnant?
• When the Pregnancy Test Is Negative...
• The Truth About Early Pregnancy Tests
• The Best Way to Take a Pregnancy Test
• You've Got a Positive Pregnancy Test!

<sub>Sources:

Heitmann RJ1, Langan KL1, Huang RR2, Chow GE1, Burney RO3. “Premenstrual spotting of =2 days is strongly associated with histologically confirmed endometriosis in women with infertility.” Am J Obstet Gynecol. 2014 Oct;211(4):358.e1-6. doi: 10.1016/j.ajog.2014.04.041. Epub 2014 May 4. http://www.ncbi.nlm.nih.gov/pubmed/24799313

Jabara S, Barnhart K, Schertz JC, Patrizio P. "Luteal phase bleeding after IVF cycles: comparison between progesterone vaginal gel and intramuscular progesterone and correlation with pregnancy outcomes." J Exp Clin Assist Reprod. 2009 Oct 20;6:6.

Snell BJ. “Assessment and management of bleeding in the first trimester of pregnancy.” J Midwifery Womens Health. 2009 Nov-Dec;54(6):483-91. doi: 10.1016/j.jmwh.2009.08.007. http://www.ncbi.nlm.nih.gov/pubmed/19879521

Vaginal bleeding in early pregnancy. Medline Plus. Accessed May 28, 2015. http://www.nlm.nih.gov/medlineplus/ency/patientinstructions/000614.htm</sub>