This is a question that runs through a lot of women’s minds- especially after missing a menstrual period & having a positive at home pregnancy test. It is common to want to know how far along you are, as soon as you find this out.
How can you calculate this?
The simplest way to figure this out is by keeping track of your menstrual period and knowing the date of when your last menstrual period started. The accuracy of this method depends on how accurately you keep track of this. If your cycle is quite regular, for example every 28 days you have your menstrual period, than this method will work to calculate how far along you are.
If you are someone with an irregular cycle, this is not as easy to calculate, using this method. To figure out the length of your cycle, you would count the days from the start of one menstrual period to the start of the next. Cycles vary from woman to woman. They can be anywhere from 21-35 days. They can also be regular and irregular. As I mentioned, you want to only use this method if your cycle is quite regular, no matter the length of it.
Once you have determined whether or not your cycle is regular and if you have accurately been keeping track of your menstrual period, you can count the weeks to find out how far along you are in your pregnancy. You would go back to the first day of your last menstrual period on a calendar and than from there, count the weeks up to the current date.
When you are calculating this, keep in mind that you do not count that first day of your last menstrual period as week one- rather that is day one. That is your starting point and you are one week pregnant the following week on that same weekday. Once you get to the current date, you will know how many weeks along you are and if you keep counting up to forty weeks, that would be your estimated due date.
To double check your calculation, you can also put your information into an online pregnancy calculator. It will ask you the date of when your last menstrual period began, as well as how long your cycle is.
How do ultrasounds help?
If you are someone that has an irregular cycle and cannot use the above method to calculate how far along you are, your doctor will be able to tell you by performing a dating ultrasound. This ultrasound discloses the presence of a heartbeat, the number of embryos and gestation sacs, as well as the size of the embryo in order to determine the gestational age.
A dating ultrasound is best done at least eight weeks along in a pregnancy, as by this gestational age, both the embryo and its heartbeat are relatively easy to detect with the trans-abdominal transducer. A trans-vaginal ultrasound may be necessary to visualize the developing embryo, if the woman is less than eight weeks along in her pregnancy.
Dating ultrasounds are also most accurate at determining gestational age and baby’s due date when performed between eight and eleven weeks gestation. This is because the embryo’s length is measured quite accurately when they are unable to bend a great deal and between eight and eleven weeks gestation, the embryo is growing at a fast rate. The difference in its size from week to week in this period is quite noticeable.
Most doctors are moving towards performing a dating ultrasound on every woman- regardless of whether or not they have a regular cycle. Certain limitations, such as having an available ultrasound machine, must be taken into consideration. Each situation is also patient dependent. The accuracy of dating ultrasounds depends on the skill of the sonographer, as well as the quality of the equipment being used.
As always, I hope this helps answer any questions you may have had in determining how far along you are in your pregnancy. For any further questions, please do not hesitate to reach out to a Mama Coach near you! We are all happy to help!