Most women determine that they are pregnant if they are sexually active and have missed a period. Nausea, breast soreness, and fatigue are also common symptoms in early pregnancy. Ultrasound or pregnancy tests are the only ways to immediately be sure that a woman is pregnant.
You can do a pregnancy test from the first day you missed your expected period and onwards. Before this time, the level of hormones produced by the pregnancy is too low to show up on the test and you may get a 'false negative' result.
If an ultrasound is performed, the doctor can tell a woman exactly how long she has been pregnant. The doctor can also estimate the length of the pregnancy without using ultrasound. A pregnancy test cannot provide this information.
A woman can also make a reasonable calculation of about how long she has been pregnant. She must figure out when the first day of her last menstrual period was, include that day and start counting up until today.
More scientific information:
Studies show that women are capable of doing this on their own.
A study was carried out to see if women in the United Sates and India could calculate how long they had been pregnant. The women were given calendars and worksheets to help them do the calculations. 98 out of every 100 women in the study group in the U.S. and 87 out of every 100 women in the study group in India were able to estimate how long they had been pregnant. Approximately 9 out of 10 women could estimate the lengths of their pregnancies accurately enough to use mifepristone and misoprostol on their own. The researchers concluded, “The vast majority of women seeking first-trimester abortion in this study could accurately calculate pregnancy duration within a margin of error clinically inconsequential for safe use of unsupervised medical abortion. Most of the women’s estimates were within 1 week of the actual length of their pregnancy. This was “well within the documented margin for safe and effective medical abortions 2 .
