Fetus Age and Ultrasound Date Disagree


Dear Midwife,

According to my LMP I am 8 weeks pregnant. I went in to see my doctor for the first time yesterday and he gave me a transvaginal ultrasound. According to the ultrasound, my baby is measuring 6 weeks.

I am really concerned because I am certain that I am 8 weeks pregnant, or close to it, because I took an ovulation predictor test and I tested positive for a pregnancy test a bit more than two weeks later.

I have an appointment to see my doctor again next week. Should I be concerned? The baby did show a heartbeat of 160 beats/minute, which helps me feel hopeful. However I am still very worried.


I would also be a bit concerned, except that 6-week babies do not usually have a strong heartbeat like yours does. I'm betting the baby was just at an odd angle and the measurement was a little off.

You might wait about 2-4 weeks and see if you can get another ultrasound to confirm the dating.

-- Cynthia, CNM. PhD.

Cynthia Flynn

Cynthia Flynn, CNM. PhD, is the General Director of the Family Health and Birth Center which provides prenatal, birth, postnatal, gynecological and primary health care to underserved women and their families in Washington, D.C. Recently Cynthia served as Associate Professor of Nursing at Seattle University. There she not only taught, but remained in full scope clinical midwifery practice at Valley Medical Center where she cared for pregnant and birthing women, and practices well-woman gynecology, family planning, and treatment of sexually transmitted diseases.

Cynthia founded Columbia Women's Clinic and Birth Center, where she took care of pregnant women and infants up to two weeks of age and attended both birth center and hospital births. Before Cynthia earned her CNM, she worked as a registered nurse in labor and delivery and postpartum and is a certified Doula and Doula trainer.