For those trying to conceive, the focus is often on timing ovulation and ensuring the sperm and egg meet, but for a fertilized egg to lead to conception, a second crucial step is required: implantation. This is the moment when the fertilized egg attaches itself to the uterus.
“After fertilization, the fertilized egg (now called a zygote) travels through the fallopian tube and undergoes several cell divisions as it travels toward the uterus,” explains Laura Shaheen, MD, FACOG, a reproductive endocrinologist and program director at Pacific NW Fertility in Seattle. “Once the fertilized egg reaches the uterus, it begins to attach to the uterine lining, a process called implantation.”
Of course, the whole process is complicated, and it’s natural that you might have questions. We spoke to experts to find out more, including when you should get a transplant and how long it will take.
What is transplantation?
Implantation is the process by which a fertilized egg attaches to the uterus after fertilization. It is a necessary step for a successful pregnancy and usually occurs 6-12 days after conception.
How soon after fertilization does implantation occur?
“Implantation typically occurs six to 12 days after fertilization,” explains Alyssa Quimby, M.D., a board-certified obstetrician-gynecologist in Los Angeles and co-founder of Female Health Education, though this range varies from person to person because it’s based on how quickly the fertilized egg reaches the uterus after fertilization.
In addition to the migration of a fertilized egg, there are several other factors that are necessary for successful implantation. These factors include adequate levels of the hormones estrogen and progesterone, adequate blood flow to the uterus, a healthy embryo, and a receptive endometrium, which is the lining of the uterus where the embryo implants.
“And they all need to be at the right stage of your menstrual cycle,” Dr. Shaheen points out. Timing is key: If the fertilized egg arrives within six days, your uterine lining may not be ready yet.
| Approximate times for ovulation and implantation based on cycle length | ||
|---|---|---|
| Cycle Length | Ovulation and fertilization | transplant |
| 28th | Day 14 | Days 20 to 24 |
| 30 Days | Day 16 | 22nd to 26th |
| 32 days | Day 18 | Days 24 to 28 |
What are the signs that the transplant was successful?
Most people will not experience any specific signs or symptoms that indicate implantation has taken place. However, some people may experience the following signs that implantation has taken place:
Implantation bleeding
A small percentage of pregnant women experience a phenomenon called implantation bleeding, which is usually just a small amount of bleeding, but depending on when the pregnancy occurs, it can be mistaken for a period or an early miscarriage.
Placement of implants
For those who keep track of their basal body temperature (BBT) according to a pregnancy calendar, there may be a drop in BBT for a day around the time of implantation. This is often called the implantation drop and may indicate pregnancy for those keeping track of their basal body temperature.
Early Pregnancy Symptoms
Typically, signs and symptoms of pregnancy don’t appear immediately after implantation. Although this isn’t always the case, most women start experiencing early pregnancy symptoms like nausea, fatigue, and breast tenderness around the time their period is late.
It’s important to note that successful implantation can occur even in the absence of obvious symptoms, says Dr. Shaheen, “However, these particular symptoms can also be caused by other factors, such as rising progesterone levels before the start of menstruation, and are not necessarily reliable indicators of implantation. The only way to confirm implantation and pregnancy is with a pregnancy test.”
When will a pregnancy test show a positive result after implantation?
“After implantation, the pregnancy hormone human chorionic gonadotropin (hCG) begins to increase,” explains Dr. Quimby. “This hormone is what causes a positive pregnancy test.” Unfortunately for those who are eager and hopeful, it often takes a while for hCG to reach detectable levels. Although it varies from person to person, hCG can usually be detected in a blood test 8-11 days after fertilization and in a urine test 12-14 days after fertilization.
“So pregnancy tests can usually detect pregnancy about one to two weeks after implantation, depending on the sensitivity of the test and the timing of the test relative to ovulation and implantation,” adds Dr Shaheen.
In fact, one of the most common reasons for a false negative pregnancy test is testing too early and your hCG levels aren’t high enough to be detected. “For the most accurate results, it’s best to wait at least a few days after your missed period before taking a pregnancy test,” says Dr. Shaheen.
Successful implantation through fertility treatment
The menstrual cycle is designed to prepare the body for successful implantation 6-12 days after ovulation or fertilization. For those using methods such as artificial insemination or in vitro fertilization (IVF) to achieve pregnancy, steps can be taken to optimize timing and increase the chances of successful fertilization and implantation.
“Depending on each individual case and your doctor’s advice, intrauterine insemination (IUI) can be timed just before or just after ovulation, with the goal of delivering sperm into the fallopian tube or uterus at a time when an egg is most likely to arrive,” says Dr. Shaheen. “Your doctor can also monitor the development of follicles in the ovaries with ultrasound to determine the best time for an IUI procedure.”
In an IVF cycle, a timing factor that plays a key role in successful conception is the timing of embryo transfer, which usually takes place on day 2 or 3 (also called cleavage stage embryo transfer) or day 5 or 6 (also called blastocyst stage embryo transfer).
Making this decision also involves making sure the lining of the uterus is ready for a fertilized egg to implant, Dr. Quimby points out, “for this reason, evaluation of the uterine cavity (by ultrasound, intrauterine videography, or intrauterine dye injection testing) is recommended to ensure there are no tumors or other abnormalities that may prevent a successful pregnancy.”
Taking all these factors into consideration will put you that much closer to successful implantation and a healthy pregnancy. Of course, if you have any further questions about conception, your menstrual cycle, or fertility, be sure to consult with your obstetrician-gynecologist or healthcare provider.
Additional reporting by Krissi Danielsson.
