The Six Most Common Signs of Implantation

pregnant-woman-and-sonBefore looking into what some of the signs of implantation might be, what transpires in the days leading up to implantation is worth reviewing. Initially, ovulation takes place. This is where the ovary releases an egg, which then enters a fallopian tube, where it remains for about a day.

If the egg, or ovum, is not fertilized, it will pass out of the fallopian tube and into the womb or uterus, where it will then disintegrate and be reabsorbed back into the body. In such an instance, there will be no implantation.

Prior to Implantation – Changing from Oocyte to Zygote to Morula to Blastocyst

After fertilization, the ovum becomes a zygote (if it is not fertilized, it remains an oocyte) and conception results. During the 48 to 78 hours immediately following fertilization, the cells making up the zygote begin to multiply. The zygote goes from being a single-cell to a two-cell state, then to a four-cell state, and then to an eight-cell state, at which time it is referred to as a morula.

On approximately the 4th day, the fertilized egg enters the uterus. It floats more or less freely within the uterus for two or three days, having undergone yet another name change. Once entering the uterus, the morula, which is now made up of 16 cells, becomes a blastocyst, although most people will still refer to it as an egg, or a fertilized egg.

Implantation – the Blastocyst Becomes an Embryo

These name changes have a purpose. As the cells within the ovum multiply, the ovum begins to take on different characteristics and undergoes structural changes. The early blastocyst (Day 5) becomes a late-stage, or hatching blastocyst (Days 6 through 8). At about the same time, the tissues lining the wall of the womb undergo changes in preparation for accepting the newly hatched egg. These changes in both the egg and the uterus are accompanied a change in hormones, hormone levels, and the creation of a specialized group of enzymes. It is from these changes that symptoms indicating implantation has occurred can sometimes be experienced. Finally, on Day 8 or 9 following conception, the blastocyst attaches itself to the uterine wall. The egg is now an embryo, a living organism attached to its mother.

Signs and Symptoms

positive-pregnancy-testListed below are some of the common signs and symptoms of implantation:

1. Frequent Urination – During pregnancy, hormones are constantly being released into the system from the corpus luteum, which is located in each of the ovaries. The primary hormone released is progesterone, a steroid hormone that is essential in establishing and maintaining pregnancy. Another hormone released is human Chorionic Gonadotropin or hCG. This hormone is secreted by the blastocyst, now turned embryo, as it works its way into the uterine wall. The hCG hormone causes an increase in the blood supply to the pelvic region, which can at times irritate the bladder, and result in the need to urinate frequently, in small amounts at a time.

2. Spotting – Spotting is probably the most common sign that implantation is occurring, and will occur during a rather narrow window, 7 to 10 days after ovulation. When spotting is observed during this time frame it is usually a pretty solid indication of a pregnancy. The color of the spotting also offers a clue. When spotting is due to implantation it is usually pinkish in color instead of a deeper red, as during menstruation.

3. Cramping – As is the case with spotting, cramping due to implantation can easily be confused with menstrual cramping. Perhaps the major difference is that implantation cramping tends to be milder, and also lasts longer. The cramping is often felt in the lower back and may last for 24 to 48 hours, as the walls of the womb undergo a continual series of contractions during implantation.

4. High Basal Body Temperature – Basal body temperature is the lowest temperature a body attains during a normal 24 hour period. It usually occurs during a period of prolonged rest, especially during sleep. The best time to measure your basal temperature is in the morning, immediately after awakening. Ovulation causes it to increase between a degree and a degree-and-a-half, and it is therefore measurable. This increase is, in most cases, a sure sign that ovulation has taken place. The temperature rise most often happens the day following ovulation, but it can occur anytime within a 3-day window.  Implantation comes into the picture when this increase in basal temperature fails to drop during, or after, the 2 weeks following ovulation and before the start of the next menstrual cycle. If implantation has occurred, the basal temperature will remain high during the first trimester of the pregnancy.
5. Breast Tenderness, Swelling, or Soreness – Rapid hormonal changes during implantation will sometimes cause the breasts to become tender or sore, or slightly swollen. These symptoms often occur during menstruation, but usually recede after a day or two. During the implantation phase, discomfort can linger for a week or more, and is therefore another positive sign of pregnancy.
6. Hot Flashes – Hot flashes are not a particularly good indicator since they often occur before or during the menstrual cycle. At the time of implantation, however, rapid fluctuations in hormone levels are taking place, and you could have a hot flash while the embryo is beginning to embed itself in the uterine wall, releasing significant amounts of the hCG hormone in the process.

As you may have gathered from the above, experiencing any single one of the signs of implantation described may not be a proof-positive indication that you are pregnant. You may in fact not experience any of these symptoms at all, which would not be unusual. However, if you experience more than one of these signs, the chances are high that you could be pregnant. If you are, use our implantation calculator here to determine your implantation date.