How to get Pregnant » Pregnancy Calculator

Pregnancy Calculator

How to Get Pregnant

A pregnancy calculator can help to determine when to expect your baby. Pregnancy can be calculated by either the date of conception, if known, or by the first day of the woman's last period, which is the way most doctors determine the due date. Those with very irregular periods, or the small percentage of women who continue to have light periods after conception, may not always be sure when they actually became pregnant. There are a few ways to help calculate when to expect your new baby.

The Pregnancy Calculator Using the Conception Date

If a woman knows the day she became pregnant, within a day or two, she and her physician can calculate the expected due date of her baby. Pregnancy is approximately 266 days from conception, which is approximately 40 weeks. This is called a fetus' gestational age. Conception happens about 14 days before your period was due.

The Pregnancy Calculator Using the Date of Your Last Menstrual Period

Using the date of your last menstrual period (LMP), you can calculate when you should expect your new addition. This is the method your physician will normally use. Pregnancy lasts approximately 280 days from your LMP, or 9 months, give or take a week or two. This is called the baby's menstrual age.

When Pregnancy Calculators Can Be Incorrect

There may be a few instances when a pregnancy calculator is incorrect. Implantation bleeding can cause a woman to believe that she's having a true menstrual period, thereby causing a miscalculation in her due date. Irregular periods, or ones that are longer or shorter than the normal 28 days, can also cause miscalculation.

When the Date of Conception or LMP Date is Unknown

There are other ways to use the pregnancy calculator if the date of conception, or last menstrual period, is unknown, or periods are irregular. You can find pregnancy calculators that will allow you to adjust it if your menstrual periods are longer, or shorter, than the 28 days normally used for calculation.

The Pregnancy Calculator Using Early Ultrasound

Many physicians will determine or confirm a baby's gestational age and due date by ordering an early ultrasound. During an ultrasound, a baby's measurements are taken. The baby's measurements will help a doctor to determine the baby's gestational and conception date, along with the approximate due date.

Knowing the Baby's Due Date Helps to Know What to Expect

By knowing the baby's due date, using the pregnancy calculator, a new mom-to-be will know what to expect for the growing uterus and their growing fetus. This helps both the mother and the doctor know when there's a possibility of a potential problem and they can make the needed adjustments.

Having an accurate due date is important because it can help to prevent misleading prenatal test results, including prematurity. Many health care providers will determine a woman's due date using a pregnancy calculator that will later be followed up by ultrasound.