Questionhello, my lmp started nov. 27 or 28th 2007. that would make my due date sept 2 or 3, 2008. i had a sonogram at 7 weeks and it was accurate with my LMP. i just recently had a sonogram for my 12.5 week checkup and the sonogram said i was 13.5 weeks. is this from the date of conception? or the date of my LMP? and how could i have gotten pregnant a week before i had my period? if i was pregnant, i wouldn't have had a period, right? it wasnt just a spotting for a few days, it started light the 27th and 28th and then i bled heavily for about 6 total days. so i got kinda confused with that last u/s. ive also been having some bleeding. i had it at 7 weeks, thats y i got the 7 week sonogram. it was done transvaginally. and at my 12.5 week checkup my doc couldnt find a heart beat by doppler, so she sent me for another sonogram, this time it was transabdominal. im just wondering how it can be a whole week before my period that i got pregnant? is it possible? and y havent they checked the sonogram for placenta previa? im worried that the bleeding may be from that. thankyou,
jill
AnswerDear Jill,
Ultrasound dating is always from the LMP. Pregnancy dating itself is always from the LMP. It tends to be confusing, I know.
The 7 week ultrasound is the one to go by. Ultrasounds done within the first trimester are considered to be very accurate in dating pregnancies. Since having the ability to visualize pregnancies via ultrasound, we have noted certain "norms" at specific gestational ages in the early weeks of pregnancies. So, by measuring the gestational sac and CRL (crown-rump length) and also noting the appearance of certain things, such as the yolk sac or heart activity, we can date pregnancies quite accurately to within a few days. Now, after the 1st trimester, babies can begin to grow at different rates due to varying factors - maternal health or lifestyle, uterine conditions, etc,... So, later in pregnancies the gestational age may actually vary a bit from what the initial dating was, but it really should never be changed. And there is also a bit of a difference in the clarity of a trans-vaginal scan and a trans-abdominal scan. T-V scans provide better visualization overall, as there is less tissue to scan through.
As for the bleeding, vaginal bleeding can occur frequently in the 1st trimester of pregnancy and may not be a sign of problems. Bleeding can be a sign of miscarriage but does not mean that miscarriage is imminent. Studies show that anywhere from 20-30% of women experience some degree of bleeding in early pregnancy. Approximately half of pregnant women who bleed do not have miscarriages. And I can with almost complete certainty assure you that if there were a placenta previa or a low-lying placenta, they would have noted it on one of the ultrasounds. Ask your doctor what the location of your placenta is according to your ultrasounds at your next OB visit. Also inquire further as to what he/she thinks the source of the bleeding is and if they feel there is cause for any further tests or intervention at this point.
I hope this has helped you and answered your question. I wish you well.
Brenda
