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Implantation Calculator: When Did It Happen?

implantation calculator

Essential Takeaways

  • 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

If you think you may have conceived this cycle, you might be looking for an implantation calculator. These little tools were developed to estimate when the fertilized egg may have burrowed into your uterine lining, thereby beginning your pregnancy. You’ll find a plethora of these nifty little calculators online promising to tell you your implantation date. But the reality is, they can’t.

Before getting into the details on why these calculators aren’t very accurate, here’s how they work. Implantation most often occurs 9 days after ovulation. Based on this information, there are two common ways to estimate when implantation occurs for you.

  1. If you know the date you ovulated, add 9 days.
Ovulation date + 9 days =  Implantation date
  1. If you know the first day of your last menstrual period (LMP), add 23* days.
Date of last menstrual period + 23 days =  Implantation date

*23 days =  14 (average number of days between LMP and ovulation ) + 9 (average number of days between ovulation and implantation)

Important note: The above calculations are a very oversimplified guess. The reality is that your cycle is variable and the day you ovulate won’t necessarily be consistent from cycle to cycle.

So while using averages like 14 days (between LMP and ovulation) and 9 days (between ovulation and implantation) will tell you when implantation tends to happen on average for women as a whole, it won’t tell you much about when implantation happened for you.

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 does implantation mean for pregnancy?

When you’re trying to get pregnant, “When did I conceive?” is a pretty common question. However, a better question might be, “When did implantation occur?”

Many people assume that pregnancy begins at conception—the moment that sperm enters the egg. 

A more accurate beginning of pregnancy would be the implantation date rather than the conception date. Implantation, or the process of the combined egg and sperm cells attaching to the wall of the uterus, marks the actual start of a viable pregnancy.

According to recent research published in Nature Biotechnology, conception occurs much more readily than implantation, but this does not ensure pregnancy. For the pregnancy to be viable, the cells must make contact with the endometrium and attach to the uterine wall.

As many as two thirds of embryos fail to implant. This indicates that embryos are likely predestined for survival or death before even the first cell division.

If progesterone hasn’t adequately prepared the endometrial lining to support life, or if the blastocyst contains abnormalities, implantation will fail. When this happens, the egg dies and is excreted during your next period.

When does implantation occur?

In most successful pregnancies, implantation occurs 8 – 10 days after ovulation. The most common day is 9 days after ovulation.

While it’s possible for implantation to occur between 6 – 12 days after ovulation, implantation earlier than 8 days after ovulation is rare.

Can you have late implantation?

According to a study published in the New England Journal of Medicine, the estimated risk of early loss is strongly related to the time of implantation. The study found that early loss was least likely when implantation occurred by the 9th day past ovulation (DPO) and the risk increased with each successive day—most substantially after day 11*.

Here are the specific results:

Implantation Date (in Days Past Ovulation) Risk of early pregnancy loss
9 DPO 13%
10 DPO 26%
11 DPO 53%
after 11 DPO 82%

If implantation occurs later, it is more likely to result in early loss or a chemical pregnancy (chemical pregnancy is the term given to a miscarriage that occurs before the fifth week of gestation, and early loss is a miscarriage that happens in the first six weeks of gestation.).

While it’s not fully understood why later implantation tends to result in early pregnancy loss, researchers speculate that embryos that are slow to implant must be impaired in some way. 

When did implantation occur for me?

Based on your knowledge of your last menstrual period or ovulation date, you can estimate when implantation might have taken place. (This is why tracking your cycle is incredibly valuable, as it can help you find out when ovulation occurs for your body, specifically.)

If you have a pretty good idea of when ovulation happened, then you can estimate that implantation most likely happened  8 – 10 days past ovulation (DPO). 

How long does implantation last?

Most of the time, implantation follows a relatively stable timeline. Sperm can live for about five days, waiting for an egg’s release. Once an egg is released from the ovary, it begins a journey down the fallopian tubes and must be fertilized within 24 hours.

If a sperm does fertilize the egg, and the resulting blastocyst makes it to the uterus, it can still take several days to implant itself in the uterine wall. In all, the entire process usually takes 8 – 10 days, though, in some rare cases, implantation may occur as early as the sixth day, or as late as 12 days, after ovulation.  

What are the signs and symptoms of implantation?

Many women wonder when they can start expecting signs and symptoms confirming their hoped-for pregnancy. Who hasn’t Googled “early pregnancy symptoms” 24 hours after sex?

However, implantation symptoms are a debunked myth. Even though many sources use the word “burrowing,” which certainly sounds like it should feel like something, implantation involves only a few cells and causes no unique pain or cramping.

In fact, the cramping people often associate with implantation cramps results from the high levels of progesterone already present during the luteal phase of your menstrual cycle.

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.

How about implantation bleeding? People talk about that all the time, right? Sorry, this one’s a myth, too. One study found that while 9% of women did experience light bleeding or spotting during early pregnancy, it was rarely on the day of implantation.

Essentially, in the very early days of pregnancy, it’s nearly impossible to differentiate between the signs of an impending period and the signs of early pregnancy.

In fact, many of the symptoms often attributed to implantation can be explained by other causes:

  • Bleeding or spotting: spotting during pregnancy an occur for a variety of reasons, and it is often benign. However, there is no evidence that implantation causes bleeding.
  • Cramping: the hormone progesterone is high during the implantation window. Progesterone slows down digestion and can cause bloating, cramping, and general abdominal discomfort.
  • Pain: Many factors unrelated to pregnancy 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.

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.

How long after implantation can I get a positive pregnancy test?

When you’ve got your fingers (and toes) crossed hoping for a positive result, there’s probably one insistent question looping through your mind: How soon can you take a pregnancy test?

Home pregnancy tests are most accurate when taken on or after the first day of your missed period, which usually occurs 12 – 14 days after ovulation.

Pregnancy tests detect the presence of a hormone called human chorionic gonadotropin, or hCG, which is unique to pregnancy. Your body doesn’t even begin producing hCG until implantation is finished—most likely 8 – 10 days after conception. Once it does, the hormone doubles roughly every 48 hours.

Not all pregnancy tests are created equal. Here are some of the best pregnancy tests on the market.

How to help implantation

If you want to increase the chances of getting pregnant, is there anything you can do to promote implantation? 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.

 

 

*Note that studies approximate when implantation occurs based on the first appearance of chorionic gonadotropin in maternal urine.


View sources

Non-invasive imaging of human embryos before embryonic genome activation predicts development to the blastocyst stage

Time of Implantation of the Conceptus and Loss of Pregnancy

Vaginal bleeding in very early pregnancy

Urinary hCG patterns during the week following implantation

Lindsay Meisel

Lindsay Meisel is the Head of Content at Ava. She has over a decade of experience writing about science, technology, and health, with a focus on women's health and the menstrual cycle. Her work has been featured on The Fertility Hour, The Birth Hour, The Breakthrough Journal, and The Rumpus.

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