Knowing how far along a pregnancy is will help determine the due date. It will also give you an idea of what to expect based on how many weeks pregnant you are. The lack of a menstrual period gives an idea of when the pregnancy started, based on the last menstrual date. However, not every woman has regular menstrual cycles. For those who do not, other ways to calculate the length of a pregnancy are necessary.
Use a measuring tape to measure the size of your belly. Hold the beginning of the tape just above your pubic bone. Stretch it out and up toward your belly button. The measured amount of centimeters is the amount of weeks pregnant you are. This will give you a general idea of how far along your pregnancy is.
Get an early ultrasound. When your menstrual period is irregular, your obstetrician may want to order an ultrasound. This early ultrasound can calculate how far along you are in the pregnancy. The ultrasound technician will measure different sections of the baby. The ultrasound machine takes these measurements and calculates your due date. Subtract the weeks from your due date to the current date to find out how many weeks pregnant you are.
Find the heartbeat. You can approximate the amount of weeks pregnant you are by the sound of your baby's heartbeat. The day your doctor is able to hear the baby's heartbeat with a Doppler ultrasound machine falls anywhere between weeks nine and 12.
Feel your baby move. The first time you may be able to feel your baby move is between the 16th to 22nd week in your pregnancy. If you feel the baby move for the first time, chances are you are somewhere in this time frame. This method does not give you a completely accurate calculation of how many weeks pregnant you are, but it does give you a general idea.
Use your last menstrual date to help you out. If you know when your last menstrual date was and you are regular, this can be a very effective method to calculate how far along you are in your pregnancy. Take the first day of your last menstrual period and add each week thereafter. This will tell you how many weeks pregnant you are.
Use an online pregnancy calculator. This requires that you know when your last menstrual period was. Many pregnancy sites offer calculators. One good site is BabyStrology. When visiting there, click on "Tools" and then "Baby Tickers." The site's baby ticker will allow you to track the development of your baby and determine how many weeks along you are in your pregnancy. It even shows a picture of a baby in the womb at the same stage of development as yours.
Keep track of your menstrual cycle on a calendar to be sure you always know when your period starts and stops.
Contact your physician if you think you may be pregnant.