Written by: Dr. Amy Beckley, PhD, Founder and Inventor of the Proov test — the first and only FDA-cleared test to confirm successful ovulation at home.
Written on 8/5/21
The implantation window is when a fertilized egg can actually make its home in the uterus.
If you’re trying to conceive, you’ve likely heard of your fertile window. These few days occur around the middle of your cycle and are the only time when conception is actually possible.
But, there is another important window you should know about: the implantation window! This is when a fertilized embryo can actually make its home in the uterus. Keep reading to learn more about implantation and when the implantation window occurs.
What is implantation and why is it important?
Implantation occurs when a fertilized embryo attaches itself to the uterine wall during the second half of your cycle. This is where it will thrive and grow into a baby for the next 9 months.
After an embryo implants, the outer layer of the cell will start to form the placenta. The uterine lining can then provide the embryo with nutrients and oxygen to help it grow.
In order for implantation to happen, the uterine lining must be receptive, meaning it’s ready to allow an embryo to implant. During the first half of your cycle, estrogen thickens the uterine lining to ensure it’s comfy enough for an embryo. Then, during the second half of your cycle, progesterone stabilizes the already thick lining and makes it “sticky” enough to allow an embryo to implant.
The presence of progesterone opens the “receptivity window” (basically when the uterine lining will be receptive to an embryo) about 7 days after peak fertility and it will remain open for about 4 days total. However, if there is not enough progesterone present after ovulation or it drops too soon, then implantation — and therefore pregnancy — may not occur.
When does implantation occur?
As we mentioned, implantation occurs during the second half of your cycle and may take place anywhere from 6 to 12 days after peak fertility. The most common days of implantation are days 8, 9, and 10 after peak fertility.
While most women don’t typically notice when implantation is actually happening, there are a few symptoms you may experience before a positive pregnancy test, including:
Cramping: Some women compare these with premenstrual cramps, but implantation cramps are more often than not just a mild discomfort. They’re typically pretty easy to overlook.
Implantation bleeding: Spotting or very light bleeding occurs sometimes around the date the embryo implants — more on this later!
Sore breasts: Sensitive breasts are often one of the very early pregnancy signs. Due to hormonal changes, your breasts may appear fuller, swollen, or feel sore, even before your period is due.
Mood swings: Mood swings might be yet another sign of successful implantation. Changes in your hormone levels may make you feel more emotional or sensitive.
It is very important to keep in mind that while these symptoms may indicate implantation, they are also often accompanied by your period and do not necessarily mean you are pregnant. The only way to confirm pregnancy is by taking a home pregnancy test, which measures HCG.
It is very important to keep in mind that while these symptoms may indicate implantation, they are also often accompanied by your period and do not necessarily mean you are pregnant.
What is implantation bleeding?
Implantation bleeding is light bleeding or spotting that occurs around the time the embryo burrows itself into the uterine lining, causing small blood vessels to burst in the process. Implantation bleeding is fairly uncommon, but some women do experience it.
Although implantation bleeding often looks different from a period, some women may mistake it for one, especially if the pregnancy wasn’t planned or if she experiences irregular periods.
Usually, implantation bleeding lasts no more than 2 to 4 days. Some women may have just a bit of pink, beige, or brown spotting, noticeable only when they wipe, while others may experience some light bleeding, although usually not enough to require a pad or tampon.
The only way to tell the difference between implantation bleeding and a light period is to take a pregnancy test! You would still likely want to wait another 48 hours after bleeding to take a pregnancy test, as it can take our bodies some time to produce HCG after implantation occurs.
While implantation bleeding that occurs around one week after a positive ovulation test is normal, bleeding in early pregnancy may not be. If you experience bleeding after a positive pregnancy test, we recommend consulting your doctor.
Three common causes of bleeding in early pregnancy that require medical attention are:
- Low progesterone
- Subchorionic hematomas
- Ectopic pregnancy
Three common causes of bleeding in early pregnancy that require medical attention are low progesterone, subchorionic hematomas, and ectopic pregnancy.
How can I support implantation?
At this point, you may be wondering if there’s anything you can do to ensure your embryo actually implants. The answer is yes!
While you may have heard of many myths that can inhibit implantation during the two week wait — like drinking coffee, having a glass of wine, or even straining too much on the toilet — the reality is that these small things won’t make a big impact on your ability to get pregnant. If you enjoy a glass of wine with dinner, there’s no need to deprive yourself of life’s simple pleasures! (And hey, we’re right there with you!)
If you do want to improve your chances at implantation, here are a few things you can try:
Ensure you have enough progesterone during the luteal phase. As we mentioned, progesterone is essential for supporting a sticky uterine lining and implantation. Proov PdG (progesterone metabolite) tests can help you ensure your post-ovulation levels look good. And if not, there are plenty of ways to increase progesterone.
Avoid anti-inflammatory medications. Studies show that taking anti-inflammatory drugs (like ibuprofen, naproxen, or aspirin) during the luteal phase may increase the risk of miscarriage by 80% and can impact the receptivity of the uterine lining. Of course, we recommend talking to your doctor before making any changes related to medicine, especially prescription medicine.
Try acupuncture. Acupuncture is known to improve blood flow to the uterus which can potentially help with implantation. If you would like to give it a try, make sure you find a certified acupuncturist, ideally one that is specialized in fertility.
Understanding when implantation occurs and how you can support it can help you get pregnant faster!