If you are actively trying to conceive a baby or have had a fertility procedure like in vitro fertilization (IVF) or artificial insemination (AI), the wait in between timed intercourse, insemination or an embryo transfer, and the greatest accuracy of results on a home pregnancy test or a Beta hCG test is around two weeks.

Known as the two week wait (2WW), this period of time can be filled with anxiety and uncertainty as the countdown to testing day progresses.

While we can't help the days pass by any faster, we can give you an idea of what might be occurring if implantation was successful.

Keep in mind that the timeline is approximate, but here is a look at what could be happening inside. There are three charts depending on approach to conception:

  • Intercourse or artificial insemination
  • 3-day embryo transfer
  • 5-day embryo transfer

What Happens After Fertilization?

The following table summarizes the approximate early developmental stages in a pregnancy achieved through intercourse or artificial insemination.

Day Post Ovulation

What is Happening Inside

0

Ovulation occurs and fertilization follows. Egg meets sperm (typically within the fallopian tubes) within 6-12 hours of ovulation. A zygote is formed.

1-2

Cell division (cleavage) starts 24-30 hours after fertilization; 2 cells become 4 cells, become 8 cells. As cell division occurs, the embryo starts to move through the fallopian tube towards the uterus.

3 While still in the fallopian tube, the embryo is solid ball containing 12 to 16 cells and is called a morula. The embryo is encased in a protective coating called the zona pellucida that prevents it from sticking. The morula reaches the uterus approximately 2-3 days after fertilization.

4

The morula is 16 to 32 cells and reaches the uterine cavity around the 3.5 to 4th day. Here the morula starts to develop into an early blastocyst. The appearance of a fluid-filled inner cavity within the cell mass is an indication of this transition. Other changes include surface cells becoming the trophoblast (which will become the placenta) and the inner cell mass becoming the embryo.

5 The blastocyst is formed and remains free-floating (unattached). The protective shell around the blastocyst, known as the zona pellucida, starts to degenerate after arriving in the uterus in anticipation of implantation. This generally occurs within 72 hours of arriving in the uterus.

6

The blastocyst makes contact with the uterine lining (attachment). This is also called apposition.

7

The blastocyst starts to burrow into the endometrium. Implantation of the embryo into the uterus starts. This is also called adhesion and is marked by increased interaction between the blastocyst and the uterine lining. Not long after, the stage of invasion starts, where penetration into the lining occurs.

Implantation cramps are possible. Most likely to occur days 7-9.

8 The early placenta starts producing human chorionic gonadotrophin (hCG) hormone. This hormone can be identified in the blood and urine of the mother as a positive pregnancy test as early as 8 to 9 days. Earlier detection depends on the amount of hCG present and the sensitivity of the testing method. With a very sensitive detection method (most likely blood test), a pregnancy test can be positive at this stage.
9-10 The blastocyst has burrowed into the uterine lining by around days 9-10.

Implantation bleeding is possible. Read more: Implantation Bleeding
10-11 As the placenta develops and releases increasing quantities of hCG hormone, the chances of the pregnancy test detecting pregnancy get better.
12 A coagulation plug forms to close off the area where the blastocyst entered the endometrium. Implantation is now complete.

14

By this time, the levels of the hormone hCG, are high enough to be detected by a home pregnancy test. However, a negative home pregnancy test is not always reliable and a blood test for hCG is more reliable. Though hCG may possibly be detected in the mothers blood from day 8 onward, it is usually tested for about 2 weeks after the day of fertilization.

Implantation bleeding may occur anytime from day 9 onward when the developing placenta encroaches upon the mothers blood circulation, but if it occurs, generally coincides with the time of expected menstruation.

15-21

The fetus starts developing in length and a body cavity starts forming. The placenta gets better defined. The heart, brain, and intestines slowly start taking form.

22-28

The heart has its basic form and now starts beating. This can be seen on an ultrasound examination.

Read More: What You Need to Know About Embryo Implantation


What Happens After a 3-Day Embryo Transfer?

After embryos are grown in the laboratory, they can be transferred into the uterine cavity on either day 3 or 5 of embryo growth. Here is a look at what could be happening inside the lab and your body with a 3-day transfer.

Days Post
3-Day
Transfer

Embryo Development

0

Egg retrieval. Fertilization with sperm or ICSI in the IVF laboratory. The fertilized egg is called a zygote.

-1

Normal fertilization is confirmed by the presences of two pronuclei - one from the egg and one from the sperm. The zygotes remain in the incubator for 48 to 72 hours and grow by dividing their cells.

-2 By day 2 the cells have started to divide and should have between 2 and 4 cells. Progression beyond the zygote stage (1 cell) is important.
1

The embryo should be around 6-8 cells. Further cell division occurs to form a sphere of 16-32 cells called morula. Once transferred to the uterine cavity, the embryo remains free-floating and gets nutrition from the reserves of the egg and from the fluid in the maternal cavity.


2

The embryo becomes a blastocyst and remains free-floating in the uterine cavity, while it continues to grow. The sphere of cells which are continuously dividing now starts developing a fluid filled cavity.

3

The expansion of the cells and the fluid filled cavity within the blastocyst causes a break in the hard outer “shell” called the zona pellucida, and the embryo "hatches" out. A procedure called assisted hatching may have been done prior to embryo transfer to assist with this.

4

This blastocyst makes contact with the endometrium (uterine lining) and attaches to a receptive location on the surface of the uterine lining.

5

The blastocyst starts to burrow into the endometrium initiating implantation. This is also called adhesion and is marked by increased interaction between the blastocyst and the uterine lining. Not long after, the stage of invasion starts, where penetration into the lining occurs.

Implantation cramps are possible. Most likely to occur days 5-7.

6

Implantation continues as the embryo settles further in. The early placenta starts producing human chorionic gonadotrophin (hCG) hormone. Though early detection may be possible, it is unlikely and depends on the amount of hCG present and the sensitivity of the testing method.

7

As the embryo approaches the mother’s blood circulation, and makes contact with it, the process of implantation is almost complete and the embryo digs no further. The placenta however keeps developing in size and width.

Implantation bleeding is possible anytime from day 7 onward when the developing placenta encroaches upon the mothers blood circulation, but if it occurs, generally coincides with the time of expected menstruation.

9-10

As the placenta develops and releases increasing quantities of hCG hormone, the chances of a home pregnancy test detecting pregnancy get better.

11

The levels of the hormone hCG, are high enough to be detected even by a home pregnancy test. However, a negative home pregnancy test is not always reliable and a blood test for hCG is more reliable. Though hCG may possibly be detected in the mothers blood from day 6 onward, it is usually tested for about 2 weeks after the day of fertilization.

12 A coagulation plug forms to close off the area where the blastocyst entered the endometrium. Implantation is now complete.

Read more: 5 Things Your Embryologist Wants You to Know About Your IVF Procedure

Read more: What You Should Know About Your IVF Lab

What Happens After a 5-Day Embryo Transfer?

After embryos are grown in the laboratory, they can be transferred into the uterine cavity on either day 3 or 5 of embryo growth. Here is a look at what could be happening inside the lab and your body.

Days Post 5-Day

Transfer

Embryo Development
0

Egg retrieval. Fertilization with sperm or ICSI in the IVF laboratory. The fertilized egg is called a zygote.

-1

Normal fertilization is confirmed by the presences of two pronuclei - one from the egg and one from the sperm.

The zygotes remain in the incubator for 48 to 72 hours, and grow by dividing their cells.

-2By day 2 the cells have started to divide and should have between 2 and 4 cells. Progression beyond the zygote stage (1 cell) is important.
-3

By day 3, the embryo should be around 6-8 cells. At this point, a single cell can be taken for an embryo biopsy for genetic screening.

A 5-day embryo will continue to grow further in the laboratory incubator. If in the incubator, they are moved to a new petri-dish with a solution similar to uterine fluid.

-4

Further cell division occurs to form a sphere of 16-32 cells called morula. That said, there should be at least 10 cells by day 4.

It is possible that up to half of the embryos previously deemed good quality will not make it through the morula stage.

1

The sphere of cells which are continuously dividing now starts developing a fluid filled cavity. This is the blastocyst stage of embryo development.

The expansion of the cells and the fluid within the blastocyst causes a break in the hard outer “shell” called the zona pellucida, and the embryo "hatches" out. A procedure called assisted hatching may have been done prior to embryo transfer to assist with this.

2

The embryo makes contact with the endometrium (uterine lining) and attaches to a receptive location on the surface of the uterine lining. This is also called apposition.

3

The blastocyst starts to burrow into the endometrium initiating implantation. This is also called adhesion and is marked by increased interaction between the blastocyst and the uterine lining. Not long after, the stage of invasion starts, where penetration into the lining occurs.

Implantation cramps are possible. Most likely to occur days 3-4.

4

Implantation continues as the embryo settles further in. The early placenta starts producing human chorionic gonadotrophin (hCG) hormone. This hormone will increase to levels where it can be identified in the blood and urine of the mother as a positive pregnancy test. Earlier detection depends on the amount of hCG present on the sensitivity of the testing method. With a very sensitive detection method (most likely blood test) a pregnancy test can be positive at this stage. Don't let this drive you crazy with early testing! Levels are likely to be within the 0-50 mIU/ml range. This is

5

As the embryo approaches the mother’s blood circulation, and makes contact with it, the process of implantation is almost complete and the embryo digs no further. The placenta however keeps developing in size and width.

Implantation bleeding is possible from day 5 onward when the developing placenta encroaches upon the mothers blood circulation, but generally coincides with the time of expected menstruation.

7-8

As the placenta develops, it releases increasing quantities of hCG hormone.

9

By this time, the levels of the hormone hCG, are high enough to be detected even by a home pregnancy test. However, a negative home pregnancy test is not always reliable and a blood test for hCG is more reliable. Though hCG may possibly be detected in the mothers blood from day 4 onward, it is usually tested for about 2 weeks after the day of fertilization.

10A coagulation plug forms to close off the area where the blastocyst entered the endometrium. Implantation is now complete.

Read more: Embryo Development 6 Days in the IVF Lab

Read more: What Are Your Options for Your Remaining Embryos?

What Happens After Confirmation of Pregnancy?

The time from the first positive pregnancy test until the first view of the baby showing signs of life (approximately 3 weeks), remain somewhat mysterious because even though there is rapid growth in the embryo, it occurs at a cellular level that is not detected by any diagnostic methods. The best way to know that the baby is growing continuously is by assessing if there is a rising level of the pregnancy hormone hCG through beta testing.