How Your Period Affects Your Chances of Getting Pregnant

Trying to conceive but not pregnant yet? Maybe it's time to look to your monthly (or not-so-monthly) period for clues about why those two pink lines haven't showed up yet on your pregnancy test.

maxi pad with blood + and - on it
Photo: Photo illustration by Sarina Finkelstein; Getty Images (2)

A monthly period can be a nuisance, but it can feel even more frustrating when you're trying to conceive and your period comes early. If you've ruled out the possibility of that early period actually being implantation bleeding, you might be left disappointed and wondering what's going on. Well, one way to look at it is that your period can be your body's way of communicating with you.

That's right: What many people don't realize is that your period can actually be a window into your health and fertility—helping you track your cycles, know (approximately) when you're most fertile, and discover clues about your chances of getting pregnant.

Factors like cycle length, how heavy your flow is, and how regularly you're getting your period are all affected by the hormones in your body that regulate your cycle, help you get pregnant, and maintain a healthy pregnancy. So, when hormone levels become off-balance, sometimes due to underlying medical conditions, stress, or extreme changes in diet, there's a good chance your menstrual cycle will get thrown off.

Here, we've highlighted several common situations people face when it comes to their monthly cycle. This information can help you know when to consult a doctor about how your period could be affecting your chances to conceive.

Missed Period

If you're trying to conceive, your period isn't showing up as expected, and you're not seeing those two pink lines you're hoping for, it's a good idea to head to the doctor to get to the bottom of the issue. That's because an irregular cycle has a two-pronged effect on your fertility.

First, it'll be much harder to pinpoint those key ovulation dates when getting pregnant is most likely. Second, and more importantly, repeatedly missing periods often indicates underlying issues that can affect your fertility. Some are more serious, while others are relatively simple to solve.

If you're wondering what can cause a missed period, outside of pregnancy, of course, there are a number of possible causes.

"PCOS is probably the best-known cause of irregular cycles. Hypothyroidism can sometimes cause amenorrhea too, as can high prolactin levels, zinc deficiency, extreme dieting or weight loss, or very intense exercise," says Lauren DeVille, NMD, a naturopathic doctor at Nature Cure Family Health in Tucson, Arizona. Many of these causes can easily be fixed or reversed with the help of your OB-GYN, who can also refer you to a fertility specialist if it becomes necessary.

Abnormal Flow

If you're getting your period every month, you're definitely ahead of the game when it comes to your chances of getting pregnant. But, your flow can also offer insight into your fertility—abnormally heavy or light periods can sometimes mean there are issues that need to be solved before conception can occur.

So, if you're not seeing a positive pregnancy test month after month despite a relatively predictable period, your flow could provide a hint as to the cause. Read on to see if any of these issues might apply to you.

Heavy Period

Having an unusually heavy period could affect your fertility, even if your period is still regular. Many possible underlying causes of very heavy periods are things that could lead to an inability to get pregnant or sustain a healthy pregnancy. These issues include things like uterine fibroids or polyps, endometriosis, pelvic inflammatory disease, or a hormone imbalance.

So how do you know if your heavy flow is too heavy? According to Jessica Shepherd, M.D., an OB-GYN at University of Illinois at Chicago, an extremely heavy menstrual flow is called menorrhagia, and is characterized by the following:

  • You bleed through a pad or tampon in less than an hour
  • You suffer from dizziness, fainting, anemia, or shortness of breath during your period
  • You bleed so heavily that you require a blood transfusion.

Light Period

When you're trying to conceive, having a light period can sometimes indicate a potential fertility problem. One of the biggest underlying medical issues that could cause a light period is polycystic ovarian syndrome, or PCOS, a condition where people produce higher than average male hormones. PCOS is one of the leading causes of infertility. But the good news is that proper medical treatment to help keep hormones on track makes it possible for many people with PCOS to have a healthy pregnancy and carry a baby to term.

In most cases, having a light period isn't anything to be too concerned about. If you've always had a pretty light period, or if it's always been on the short side, this is unlikely to affect your chances of getting pregnant. But if your light flow is a sudden change that can't be explained by increased stress or dramatic weight loss, you may want to look into what's causing such a minimal period.

Cycle Length

Both an abnormally long or short menstrual cycle can impact your fertility. Drastic differences in cycle lengths can signal issues like hormonal imbalance or other underlying medical issues.

A picture-perfect cycle length is 28 days. But of course, we're all different, so there will always be some variation in cycle length. Often, one person's cycle can be off by a day or so, and that's just fine.

According to Shady Grove Fertility Clinic, "The length of your cycle, while not on any form of birth control, can be a key indicator to hormonal imbalances and whether or not ovulation is occurring in a regular manner. Hormonal imbalances can affect if and when ovulation occurs during your cycle."

Long Cycle

A long time between periods can mean you aren't ovulating regularly. In fact, long cycles are often indicative of an anovulatory cycle—that's a cycle where your body doesn't release an egg at all. As you can imagine, not ovulating can definitely make the baby-making process more challenging.

When you're trying to get pregnant, even a 30-day cycle can feel like an eternity, right? However, it's not usually an issue if your cycle just happens to be a few days longer than average. Also, rest assured that occasional cycles that are longer than usual are pretty normal. Minor things like travel, stress, or even illness can delay your period by a few days or so. But if you're going on 45 days or more, or if longer-than-average cycles are becoming the norm for you, it's time to figure out what's going on.

Many of the things that cause missed periods and other anomalies are the same things that cause super long cycles. Hormone imbalance in the thyroid and adrenal glands, uterine polyps or fibroids, PCOS or obesity can all play a role.

Short Cycle

On the flip side, if you've noticed that your period comes early or you're getting your period more than once each month, there's a good chance your cycle length may be abnormally short. If you're thinking this equates to even more chances to try to conceive, sadly, that's not always the case. An abnormally short cycle can be an indication of, among other complications, a luteal phase defect.

"The luteal phase is the second half of the cycle, after ovulation. During this phase, progesterone rises to nourish the endometrium in case of implantation. It takes about 7 days after ovulation for implantation to occur, so a luteal phase shorter than this makes pregnancy unlikely. Ideally, you need the luteal phase to last around 14 days," says Dr. DeVille.

Other signs of a luteal phase defect include spotting and repeated early miscarriages. The solution often lies in fertility drugs like Clomid or progesterone suppositories. So, if you are diagnosed with a luteal phase defect, know that it's typically a treatable problem and you'll likely have little trouble conceiving once it's corrected.

Interestingly, research also shows that while short-term fertility may be lessoned for those with a shorter luteal phase, rates of conception after 12 months of trying are often similar to those with longer menstrual cycles.


While spotting between periods can happen from time to time, if you're experiencing regular spotting before your period starts every month, or if you're having lots of breakthrough bleeding between cycles, your hormone levels may be slightly out of whack. Spotting is more common during the first few years after your period starts and as you approach menopause.

Dr. DeVille says, "spotting usually occurs when progesterone levels are too low to keep the endometrium in place. Or alternatively, if estrogen levels are too high." You could consider trying one of the new at-home hormone tests if you're having lots of mid-cycle bleeding, then take the results to your doctor. They can review your test results and determine what type of treatment you might need to increase your chances of getting pregnant.

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