For most pregnant women the very first and earliest possible sign of pregnancy is a missed period. These typical symptoms usually do not usually appear until after the hCG levels have risen to significantly high levels, usually weeks after implantation, after you miss your period, and usually after the urine pregnancy test has already become positive.
The typical earliest possible signs of pregnancy depend mostly on hCG levels and are usually induced by the hCG hormone.
The earliest possible symptoms of pregnancy include:
The egg is fertilized by the sperm inside the fallopian tube, usually within 12 hours after ovulation. The embryo then travels down towards the uterus, increasing in size and cells along the way. Right after fertilization, when there is only one cell, it's called a "zygote", and as it divides it becomes first a "blastomere" until it reaches about 30 cells, and about 5 days later, shortly before implantation, it's called a "blastocyst".
Implantation happens when the fertilized egg, the blastocyst at this time, a cluster of tiny cells, smaller than the head of a pin, has completed its travel through the fallopian tube and attaches to the lining of the uterus. It is at that time when you first experience the earliest possible signs of pregnancy. Implantation can happen between 6-12 days after ovulation with an average of about 9 days.
At the time of implantation, the blastocyst connects to the mother’s blood system and sends the hCG hormone into the mother’s blood circulation where it can be detected about 3-4 days after implantation. hCG can be detected with a positive urine pregnancy test a couple of days later.
On the day of implantation or shortly thereafter most women have usually no specific symptoms, no cramps or bleeding. However, some pregnant women experience cramps or a couple of drops of bloody discharge, so-called ‘implantation spotting’ about a week after ovulation.
Implantation spotting as an earliest possible signs of pregnancy is the exception, not the rule. Most pregnant women will likely not have spotting or cramps on the day of implantation.
There is insufficient scientific evidence to correlate certain early changes in the temperature chart, such as a dip (‘implantation dip’), or a third rise in temperature ('triphasic curve') to implantation or pregnancy.
Many pregnancy fertility charts do not have typical temperature changes like dips or triphasic patterns. And many triphasic charts or charts with dips turn out not to be pregnancy charts.
Neither a triphasic curve nor an "implantation dip" are sufficient enough evidence that pregnancy has happened and it gives too many women false hope, while the absence of a dip or triphasic pattern can still mean that the woman is pregnant.
Among your best earliest possible signs of pregnancy is a positive pregnancy test or when on the temperature curve your biphasic temperature is elevated 16 or more days after ovulation without a menstrual period.