Implantation: Signs, Symptoms, and When it Occurs
Medically reviewed by Samara Laxineta, RN on July 19, 2019
- Implantation usually occurs between 8 – 10 days after ovulation, with the most common day being 9 days after ovulation
- It’s rare for implantation to occur earlier than 8 days after ovulation
- The risk of miscarriage increases with late implantation
Implantation—the process of the egg implanting in the uterine wall—is the part of the conception process that marks the true beginning of pregnancy. Even though your gynecologist considers the first day of your pregnancy the first day of your last menstrual period, your pregnancy hasn’t begun until the embryo has implanted in your uterine wall.
We often assume that pregnancy begins at conception—the moment that sperm enters the egg. But it makes more sense to consider the time when the fertilized egg successfully implants into the uterine wall as the true beginning of pregnancy.
Why? Well, implantation may be a bigger hurdle to clear than fertilization. According to recent research from Stanford University School of Medicine, as many as two thirds of fertilized eggs fail to implant. This indicates that embryos are likely predestined for survival or death before even the first cell division.
What is implantation?
Implantation is the process of an embryo attaching to the uterine lining. This attachment to the uterine lining is what allows the embryo to receive oxygen and nutrients from the mother, and continue to progress and grow into a fetus.
As soon as implantation is complete, the embryo begins to produce the hormone hCG. This is the hormone that turns a pregnancy test positive. HCG plays an important role in early pregnancy. When you are not pregnant, a drop in the hormone progesterone is what causes your period to begin (progesterone is the hormone that maintains the uterine lining). But the presence of hCG sends a signal for progesterone production to continue, and your uterine lining is maintained throughout your pregnancy.
What are the signs and symptoms of implantation?
While it can be tempting to pay close attention to physical sensations in your body when you’re trying to get pregnant, the truth is, there are no physical signs or symptoms of implantation. If you’re wondering what implantation feels like, remember that the embryo is about half the size of a dust mite—not large enough to cause cramping, pain, or other physical sensations.
The only true sign that implantation has occurred is the presence of the hormone hCG in blood or urine, which you can detect with a home pregnancy test.
You may hear stories of women who experience implantation symptoms, but these can be explained by other causes:
- Implantation bleeding: Bleeding can occur during early pregnancy for a variety of reasons, and it is often benign. However, there is no evidence that implantation causes bleeding.
- Implantation cramps: There is no physiological reason why implantation would lead to cramping. However, the hormone progesterone is high during the implantation window. Progesterone slows down digestion and can cause bloating, cramping, and general abdominal discomfort.
- Implantation pain: The implanting embryo is very tiny, and not large enough to cause pain. There are many, many things that can cause abdominal pain, and when you’re trying to get pregnant, you’re paying closer attention to physical sensations. This can lead to mistakenly attributing the source of pain to implantation.
When does implantation occur?
A study published in the New England Journal of Medicine approximates that implantation can occur between 6 – 12 days after ovulation, and that implantation earlier than 8 days after ovulation is rare.
This study approximated when implantation occurs based on the first appearance of human chorionic gonadotropin (hCG) in a woman’s urine. Based on this method, the study found that implantation occurs between 8 – 10 days after ovulation. In the study, 84 percent of women experienced implantation during this time period, with the most common day being 9 days after ovulation.
Understanding this helps explain when to take a pregnancy test, and how to avoid a false negative pregnancy test. It usually takes 1 – 2 days after implantation for hCG levels to be high enough to be detectable. This means that it’s unlikely that you would get a positive result earlier than 9 days after ovulation (and more likely at 12 days after ovulation).
You can use our implantation calculator to determine when implantation may have occurred for you.
Can you have late implantation?
While implantation might happen later than 12 days after ovulation, the risk of early pregnancy loss increases the later implantation occurs. A study published in the New England Journal of Medicine found that 13% of pregnancies that implanted at nine days after ovulation resulted in early loss. For pregnancies that implanted at 10 days after, that figure rises to 26%; for pregnancies 11 days after, it’s 52%; for pregnancies 12 or more days after, it’s 82%.
The reason for the increased miscarriage risk with later implantation may be due to the fact that unhealthy embryos develop and implant more slowly. In other words, it’s not that a healthy pregnancy failed because it implanted too late, but rather that late implantation is a sign that the pregnancy may have been doomed from the start.
How to help implantation
Is there anything you can do to increase the likelihood that implantation will occur? The likely answer is no. There is little you can do to prevent a healthy embryo from implanting.
That said, there are a few things you should avoid doing during implantation.
- Taking anti-inflammatories: A study published in the BMJ found an 80% increased risk of early miscarriage with anti-inflammatory use around the time of conception.
- Hot tubs and saunas: There aren’t any studies investigating the impact of hot tubs and saunas on pregnancy rates. If you want to be on the safe side, you can follow the same advice as pregnant women follow: keep the heat below 103 degrees Fahrenheit) and take breaks every 10 minutes. Warm baths are okay!
- Intense exercise: A study published in the journal Obstetrics and Gynecology looking at women undergoing IVF found that those who exercised 4 or more hours per week were twice as likely to have implantation failure. Keep in mind that these results may not apply to the general population, and that moderate exercise is good for fertility (and general health!).
What is an implantation dip?
An implantation dip is a decrease in basal body temperature temperature that occurs on a single day during the implantation window (between 6 and 12 days after ovulation). Women who track their cycles using the temperature method will notice that if they become pregnant, temperature will remain elevated. The reason for this is that the hormone progesterone is elevated during pregnancy, and temperature is influenced by progesterone levels.
It’s often said that a brief drop in temperature during the luteal phase is not a sign that your period is coming, but rather caused by the implantation process and therefore a sign of pregnancy.
There are no formal studies investigating implantation dips, but the fertility tracking app Fertility Friend has run an analysis on 117,000 cycles to investigate this phenomenon. The analysis found that the so-called implantation dip is more common in cycles that result in pregnancy: 11% of charts with this pattern did not result in pregnancy, and 23% of charts with this pattern did result in pregnancy.
However, Fertility Friend’s analysis did not produce any evidence that the dip in temperature is caused by implantation. Fertility Friend study found that this type of dip was most likely to occur between 7 and 8 days after ovulation, but implantation most often occurs 9 days after ovulation.
Another explanation for the dip in temperature is that estrogen levels briefly increase during the middle of the luteal phase—often between 7 and 8 days after ovulation (estrogen has a suppressing effect on basal body temperature). It’s possible that cycles resulting in pregnancy are more likely to have stronger luteal phase estrogen surges, which could explain the higher frequency of the implantation dip in conceptive cycles.