Every pregnancy requires a fertilized egg, which attaches itself to the uterine lining. Whether this happens naturally or with assistance does not matter. When a sperm cell has fertilized an egg cell, which has implanted in the uterine lining, then one is pregnant.
The Fertilization
Most have heard the stories of the flower and the bee in their younger years, and it is this tale that becomes reality when a woman becomes pregnant.
For a pregnancy, a mature egg and a sperm cell are needed. The egg matures in the woman's ovaries, and the mature egg will release during ovulation. The egg will travel from the ovary through the fallopian tube and later to the uterus. A generally mature egg has a lifespan of about a day, while sperm cells can survive 2-5 days. This is why there is also a higher likelihood of becoming pregnant in the days around ovulation.
The egg can be fertilized during intercourse. During intercourse, both along the way, but mainly at the man's ejaculation, sperm cells swim up through the vagina. The sperm cells will move up through the cervix and into the uterus. After that, they will swim out through the fallopian tubes, and it is usually here that the sperm cell will meet the mature egg.
If a single sperm cell manages to penetrate the egg cell, the egg will now be fertilized. The fertilized egg will travel from the fallopian tube (most often) to the uterus, where it implants itself.
If the egg implants itself in places other than the uterus, it will still be referred to as a pregnancy, but unfortunately outside the uterus. A pregnancy cannot develop outside the uterus, and thus there can be pregnancy symptoms due to increasing levels of pregnancy hormones, but the fetus will not be able to develop, and the pregnancy will be lost early.
The Early Stages of Pregnancy
Very few are aware that they are pregnant in the first few weeks, as most discover it in connection with a missed period or pregnancy symptoms. However, these first weeks still count in the overall picture of pregnancy.
The first weeks of pregnancy are a bit special because weeks are counted from the first day of the last menstruation in the big pregnancy calculation. This means that the days/weeks when the egg is fertilized and implants in the uterus are also included.
When menstruation begins, there are theoretically 2 weeks until ovulation and any fertilization takes place. This is only applicable for women whose menstrual cycles are regular.
How are weeks counted in a pregnancy?
The traditional way to find the due date is based on the same calculation, where one counts 40 weeks from the first day of the last menstruation. So the egg will be fertilized precisely 2 weeks after the first day of menstruation, and from the date of fertilization, there will be 38 weeks until the baby is born. Thus, a total pregnancy of 40 weeks.
However, a typical pregnancy will average between 37 to 42 weeks. Pregnancy is counted in completed weeks, and therefore terms such as 21+2 are used. This example means that the pregnancy has lasted 21 full weeks + 2 days. At this point, one would say that you are pregnant in week 22, as it is the 22nd completed week.
Size of the fetus
In these weeks, the fetus is still so small that it doesn't make sense to specify its weight and length. In the first month, the tiny embryo will be about the size of a poppy seed, and thus will be <1 mm.
However, over the next many weeks, it will grow at lightning speed, and without you having to do anything, it will acquire all the necessary traits so that it will be ready to meet the big world.
Advice for partners
If you have a strong desire to become pregnant, you may quickly feel a bit left out as the partner who does not carry the pregnancy. Do what you can to be supportive, and remind each other that it is a joint project.
It doesn't matter how you try to become pregnant. If you are trying naturally, it can be beneficial to maintain the other joys and motivations that come with intimacy and sex.