I’m Pregnant! How do I determine my due date?

Knowing your due date is important for tracking your pregnancy’s progression and your baby’s growth.  Your medical provider can help determine your due date based on your last period date, conception date, or IVF transfer date.  If you would like to estimate your pregnancy’s due date before seeing your practitioner you can use a Pregnancy Calculator and enter one of your known dates listed above.

Another way to estimate your delivery date is to subtract three months from the first day of your last period and add seven days.  For example, if your last period started on May 5th, you’d count back three months to February 5th  and then add seven days, which means your due date would be February 12th.

What do these dates mean?

First Day of Your Last Menstrual Period (LMP) Date

Your LMP or first day of your last menstrual period is often the primary measure used to calculate a due date.  Usually you will deliver 280 days (40 weeks or about 10 months — also known as 10 lunar months) from the first day of your last period. However, if your periods are not regular or are not 28 days apart, your due date may be different from the “280-day rule.”

Conception Date

Even though your LMP can be used as marking the beginning of your pregnancy, you are not actually pregnant until you conceived (the date you got pregnant).  If you know the day or possible dates of conception this can be used to estimate your delivery date, and it is important to share this information with your medical professional.  Childbirth normally happens approximately 38 weeks after conception (approximately 2 weeks after your last LMP).

In Vitro Fertilization (IVF) Transfer Date

According to the Centers for Disease Control and Prevention (CDC) there are more than 250,000 assisted reproductive technology cycles performed in the United States each year.  If you have underground IVF and know your transfer date you can calculate your due date more precisely using this date.


Are you unsure of the first day of your last menstrual period or when you actually conceived?  Not to worry, an ultrasound can help your healthcare provider determine your due date accurately.  Plus an ultrasound early in your pregnancy can give your medical provider additional important information regarding your pregnancy and assure you that your pregnancy is viable.  A low-cost, high quality pregnancy test with an ultrasound can be scheduled with us now at https://obria.org/santa-ana/

The World Health Organization (WHO) defines a normal pregnancy to term will deliver between 37 to 47 weeks.  The differences in a due date can be from serval factors including age, length of previous pregnancies, and weight of the mother at birth.  Keep in mind that only 4% of women deliver at 280 days and only 70% deliver within 10 days of their estimated due date, even when the date is estimated by ultrasound.

Your monthly cycle and Pregnancy…

Your monthly cycle is very intricate and is designed to prepare for, and potentially support, a healthy pregnancy each month.  In each menstrual cycle you have many different hormones working together to possibly accomplish a pregnancy, with the key players being follicle-stimulating hormone (FSH), estrogen, the luteinizing hormone (LH), and progesterone.  Through Fertility Awareness you can learn about the function of your reproductive system and know more about your cycle; including your last menstrual period, length of your cycle, or any irregularities in your cycle.  This awareness can help you to achieve (or prevent) pregnancy by helping you identify when you ovulate and your fertile window.



Would you like to know more about your reproductive system, your monthly cycle and fertility awareness?  We have qualified Fertility Education Medical Management (FEMM) professionals who can help you!

If you would like to schedule a pregnancy test with an ultrasound, are looking for prenatal care, or are interested in our FEMM Fertility Awareness program you can make a confidential appointment by calling 714-516-9045 or online at https://obria.org/santa-ana/   Or if you have a question that you would like answered right away you can chat or text a nurse by downloading our free, confidential app at Obria Direct.  Find Obria Direct on the Apple Store or on Google Play. 


Book your appointment now for caring and comprehensive care!


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