You will find that the sonographer at your first ultrasound scan often called the dating scan will give you a more accurate idea of how many weeks pregnant you are by measuring your baby from its head to its bottom to form a determination. In a typical pregnancy, an expectant Mum will be pregnant for about 40 weeks or days before giving birth. You can read more about the three trimesters in this article about the stages of pregnancy. This pregnancy calculator uses one of two methods to work out when your baby might be born.
If you fill in the start date of your last period, it takes that date and adds 40 weeks assuming you've chosen a 28 day average cycle. If you've chosen a different cycle, it will add or subtract days based upon that.
If you choose to calculate by ultrasound date, the calculator will work out your due date based upon how far along you are on that date.
This will likely yield a more accurate result. German obstetrician Franz Naegele created his formula in and it has been referenced ever since. It is important to remember that this pregnancy calculator is meant to be a bit of fun and the results contain guesswork as with all 'predictions' about the future. Assuming it will be born naturally, there's obviously no way of knowing for certain when your baby will arrive.
Human gestation takes about 38 weeks. But very few expectant moms know exactly when they conceived. Even if you only had sex once during your fertile period , you wouldn't conceive on that day unless you happen to be ovulating.
Sperm can live for up to five days inside your fallopian tubes. So, it could be up to five days after you have sex that you release an egg ovulate and it gets fertilized by a waiting sperm. That's the day you conceive. The most common way to calculate your pregnancy due date is by counting 40 weeks from the first day of your last menstrual period LMP.
And that's how most healthcare providers do it. If your menstrual cycle length is the average length day cycle , your menstrual cycle probably started about two weeks before you conceived. This explains why pregnancies are said to last 40 weeks instead of 38 weeks. This method doesn't take into account how long your menstrual cycle actually is or when you think you might have conceived.
But generally speaking, women typically ovulate about two weeks after their menstrual cycle starts. And women are more likely to know when their last period started than the day they ovulated. If you do happen to know precisely when you conceived — say, if you were using an ovulation predictor kit or tracking your ovulation symptoms — you can calculate your pregnancy due date based on your conception date.
Just choose that calculation method from the pulldown above and put in your date. Note: Again, you don't necessarily conceive on the day you have sex. Date of Conception. Date of Transfer. Date of Ultrasound. Medically Reviewed by Aaron Styer, M.
Medical Review Policy All What to Expect content that addresses health or safety is medically reviewed by a team of vetted health professionals. How to Calculate Your Due Date. First day of last period Most pregnancies last around 40 weeks or 38 weeks from conception , so typically the best way to estimate your due date is to count 40 weeks, or days, from the first day of your last menstrual period LMP.
Conception date Calculating your due date based on the first day of your last period works well for women who have a relatively regular menstrual cycle. IVF transfer date There are more than , assisted reproductive technology cycles performed each year in the United States, resulting in about 77, or more babies born a year, according to the Centers for Disease Control and Prevention CDC.
The size of your uterus, which will be noted when your initial internal pregnancy exam is performed, can also be a factor in pinpointing the EDD. Can I plan my due date? Ultrasound in the first trimester is the most accurate method of dating pregnancy.
If there is a significant difference between gestational age according to LMP and gestational age according to the ultrasound, you may be given a new gestational age and due date based on the ultrasound measurements. Your pregnancy may also be dated by ultrasound measurement if an LMP formula was not appropriate for your pregnancy for any reason. LMP formulas are not suitable in several situations including the following: LMP is not known or is not certain, birth control pills were taken in the two months before LMP, the menstrual cycle is irregular, you are carrying multiples twins or more.
Although the age of pregnancy based on ultrasound measurements is more accurate than the age of pregnancy based on LMP, both are estimates and not definitive statements. The age of pregnancy can also be estimated by measuring the levels of hCG Human Chorionic Gonadotropin in the mother's blood.
The results of this test indicate how far the pregnancy has progressed. Home pregnancy tests are available which can be used in the early stages of pregnancy to measure pregnancy progress. Other, less important methods used by health professionals for assessing the age of pregnancy include measurement of fundal height size of mother's belly , the age of baby's first heartbeat, and time when mom first feels baby's movement.
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