I have been really worried about my latest US and I would really need some help...

I use to have long cycles (around 32-35) and my first US was done when I thought I should be around 6-7 weeks GA (based on 33-14 for the ovulation time). The first US showed 8 weeks GA which would mean that I ovulated around 9-10 days after the beginning of my periods (which would mean a cycle of less than 24 days? ).

My second US was done this week at what would be 21-22 weeks using my calculations on my periods: the GA shown on US was consistent with my calculations but would mean that the first US would be wrong by nearly 10-12 days. I read that the first US is always the most precise (by at most 1 weeek)... Should I fear the baby is not growing well because there is around 12-13 days difference between the two US or should I just discard the first US?

Thank you so much for your answer... I feel so worried...



Corinne

Hi coco__sweden... welcome to AMHD,

Earlier ultrasounds tend to be the more accurate as babies tend to follow a uniform pattern of growth early on... give or take several days. Later in the pregnancy, scans are less reliable for dating a pregnancy as babies will tend to grow at slightly varying rates. Later scans are better for detecting possible developmental problems.

You likely ovulated at a different time than perhaps you expected. Not everyone ovulates, for example, 14 days after the first day of your period, which is often touted as fact. Many women will ovulate a bit sooner or later which would be normal for them.

Sometimes it can be down to human error, sometimes it can be how well trained the person taking measurements is, etc. If your midwife or doctor is concerned about baby's growth, they will let you know.

Wishing you a smooth journey through the rest of your pregnancy!