The embryo reaches the uterus about five days after ovulation. At this time, the embryo has 50 - 100 cells and is called “blastocyst”. It will and must expand and hatch through its eggshell so that the cells can grow into the endometrium of uterus.
This is known as the “implantation”. The embryonic cells that grow into the endometrium of the uterus continue to proliferate.
They make the hormone, Human Chorionic Gonadotropin (HCG), which is measured in the blood or urine to confirm that a woman has successfully conceived.
Once implantation is established, most of the chance pregnancy should be fine. However, we still need to be concerned about the possibility of miscarriages. Several factors may be encompassed including the age of woman. Older women have higher chances of miscarriage than younger ladies.
The best way to know if the pregnancy progresses well is to follow blood HCG levels during the first two (2) weeks after implantation, and observe pregnancy by ultrasound.
A fetal heart beat can be seen by ultrasound at 6th - 7th weeks of gestational age, which is 4 - 5 weeks after ovulation.
The ovary continues to make hormones (estrogen and progesterone) to support the pregnancy before the end of the first trimester (about 13 weeks). After that, the pregnancy will be supported by itself.