You can always resort to ultrasound later if there are facts that just don't line up or if anything seems unusual for the date you have.
Once your body starts producing the pregnancy hormone human chorionic gonadotrophin (h CG), your periods will stop.
- date of any pregnancy tests taken and results (most tests positive at about 4 weeks pregnancy) - whether your baby's heartbeat can be heard with a fetoscope (usually not until about 16-17 weeks if you've had a baby before, not until almost 20 weeks if you are a first-timer) - when your baby's heartbeat can be heard with a Doppler (as early as 9-10 weeks if you've had a baby before, a few weeks later for first-timers) - measuring the height of your uterus, although this can vary from person to person and isn't really accurate until about 20 weeks. - cervix will change and soften between 6-10 weeks and will be visibly purplish upon exam!
- how your uterus feels, from the outside (can feel it start to protrude out of the pubic bone at 12 weeks) and the inside (feels larger than normal by 7 weeks).
- Last bleeding, to determine if it was a normal menstrual period or lighter bleeding which may have been implantation bleeding.
Plus, menstrual history in general, length of cycles, etc.
If you're only just pregnant, she may suggest that you have a blood test to check your hormone levels, or she may refer you for an early scan. I didn't appear to miss my period at all- I have light period anyway and was surprised when it came a few days early but when I missed the next one and found out I was pregnant I was a little shocked to find out I was 6 weeks pregnant which at the time didn't seem possible but I think I just mistook the implantation bleed for a period.You should also be offered a routine dating scan once you are between 10 weeks and 13 weeks plus six days pregnant. National Collaborating Centre for Women's and Children's Health, NICE Clinical Guideline. This is the most accurate way of calculating your due date. Beauty & Self Books & Music Career Computers Education Family Food & Wine Health & Fitness Hobbies & Crafts Home & Garden Money News & Politics Relationships Religion & Spirituality Sports Travel & Culture TV & Movies Guest Author - Maryn Leister So, you don't have a last period date to go on, or you're cycles are irregular enough to not know which end is up. But for those opposed to ultrasound (or for those just wanting that first pregnancy challenge) there is another way. For so many women it is, and many doctors insist on routine ultrasound when there isn't a period date to go on.