How to Know How Many Weeks Along a Pregnancy Is

Discovering that you are pregnant can be a thrilling and terrifying experience.
The first question you have will likely be, Just how pregnant am I? Typically, when you hear women respond to this question, they answer using months. But medical professionals keep track of pregnancies by counting the weeks past your last menstrual period. Though the length of pregnancies vary greatly, most providers will say that your baby is due to arrive 40 weeks after the first day of your last menstrual period.

Things You'll Need

• Calendar
• Record of the first day of your last menstrual period

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Instructions

• 1

  Recall the first day of your last menstrual period or LMP. This is the day that you started bleeding. If you have irregular periods or were not anticipating a pregnancy, you may have difficulty remembering what day your period began. If you can't remember the exact day, let your provider know. This is not a reason for concern. He or she just may take that fact into account when ordering tests or measuring your uterus later in the pregnancy.

• 2

  If you cannot recall the exact day of your last menstrual period, or LMP, it is fine to use an approximate date simply for the purposes of determining how far along your pregnancy is by weeks. The date of your last menstrual period can help you determine your due date, which is 40 weeks after your LMP. But remember, only 5% of babies are born on their due date!

• 3

  Find the day that is exactly 1 week after the first day of your last menstrual period using a calendar. On this day, you are 1 week pregnant.

• 4

  Number the weeks after your the first day of your last menstrual period. For example, if the first day of your LMP was November 1, you would be 2 weeks pregnant on November 15. You would be 3 weeks pregnant on November 22 and 4 weeks pregnant on November 29.

• 5

  Write down the number for each consecutive week on the calendar. Continue until you reach 40 weeks. This is your due date.