Measuring three weeks big in third trimester

[bcr3926]

I had my first ultrasound on July 1st and could only see a 9mm gestational sac but no yolk sac or fetal pole. My second ultrasound was on July 15th, everything was visible this time and they measured the baby at 7w1d. I went for another ultrasound on September 30th (18w1d) and the baby was measuring 19w2d (1w1d big). Today, at 30 weeks, I had my third trimester ultrasound/growth scan. The baby was measuring at 32w5d (2w5d big) and weighed 4.5lbs. My due date is March 1st but I'm wondering if it's possible that I'm actually further along than the doctor's originally thought and with so many different measurements which one do I trust? Is it possible that my 7 week ultrasound was three weeks off? That would mean my 5 week ultrasound was actually 8 weeks but there wasn't a yolk sac or fetal pole.

 

[Spudtastic]

I've always been told that earlier ultrasounds (between 6 and 8 weeks) are more acurate so I think go by your 7 week 1 day one. My babies never had their due date adjusted even though they measured ahead at 13 weeks.
Also the growth scan is only accurate to + or - 1 lb. My friends 36 week ultrasound measured her baby at 6 lb 11 and two weeks later her baby was born at 6 lb 7.
You may also just be having a bigger baby.

 

[Spudtastic]

Also babies go through growth spurts too. You may have just had one.

 

[Buttercup84]

Growth scans aren't 100% accurate and can actually vary by a fair bit. In most cases a 12 week dating scan, or thereabouts, would be accurate. I'm measuring 5 weeks ahead in fundal height and growth scan showed a large baby but I know I'm definitely not further along than my dating scan said.