(Image source from: What happens in first week of pregnancy?})
During week 1 of pregnancy your body prepares itself for Ovulation. Ovulation time is the time when ovule or ovules release from ovary or ovaries. Usually one ovary or egg is released every month from any of the ovaries. Chances to become pregnant are high during ovulation period if you are sexually active with your partner. Thus, during week 1, your body prepares for pregnancy. There will not be any sign of baby or embryo during first week of pregnancy. The released ovule awaits fertilization. If fertilization occurs, you will hear good news soon. Incase fertilization does not occur, the egg would dissolve and gets degenerated along with your uterine lining that is getting ready for pregnancy.
Your body works really hard during this week of ovulation, as it is preparing itself for a baby. Thus during this time, your basal body temperatures would rise little. You will also be able to figure it out if you keep a track of the basal body temperatures. Moreover, you would start getting into sex mood by now. If you are a TTC couple, this is the best time to go under sheets, as the fertilization window is open. These four to seven days, sperms have good chance of meeting ovum.
Every month, roughly 20% chances are there for you to become pregnant. Having sex during this time of fertile window is very important. Your ovum will wait for a couple of days for pregnancy to occur, as the sperms try to reach it. Meanwhile, even the sperms, which have entered from your partner, could wait for some days before they finally begin to move towards your ovum.
Besides these factors, your age, general health and wellbeing, determine your chances of pregnancy. In most cases, TTC couples would be able to conceive within six months, provided they are healthy and things work out on the right time. Most couples would take close to one year to hear the good news.