Could my doctor be wrong about my due date?

Question

Here is a little back story to my question: 
I tend to have a longer cycles than most
 (33-36 days). My last period started on November 5th. When we first started trying to conceive, I took a Clearblue ovulation test that said I was most fertile on November 26th. Then we found out we were expecting on December 8th 😍 (FTM)
Fast forward to now: 
After downloading multiple apps (5 to be exact 😬) and taking multiple due date calculators online, they estimated my due date for August 17th. That would put me at 17 weeks 4 days. 
However, when I went to my doctors office, they gave me a due date of August 18th, but said I was only 16 weeks 3 days. 
Question: Could all these apps and online tests be wrong or could my doctor be wrong about how far along I am? When people ask me how far along I am, I don’t know what to tell them! Plus I like measuring how far along I am week by week. I’m so confused!

Answer

Go by the MD measurement. They measure your fetus on the ultra sound at the first appointment and measurements are very easy to take in the first trimester and quite accurate. 
That being said, due dates are a guesstimate anyway... how many women do you know that went into labor exactly on their due date? I know one out of probably 30-40...

Answer

Listen to whatever your doctor said confirmed by your dating ultrasound.

Answer

Your due date is always based on your first ultrasound date.

Answer

Go by the ultrasound date. Sometimes you can ovulate later than normal and going by the last missed period isn’t accurate. I’m 6 days less far along than what my last missed period said

Answer

If you cycle length typically is 33-36, 16+3 is correct if you had a 36day cycle that month. And remember that it’s an estimate.

Answer

Doctors go by how developed the baby is to determine your due date

Answer

According to the apps I was 8 weeks when I went to my dating scan. The scan showed I was only 5 weeks. All my scans after that were right on the nose for what my dr said. Go with what your dr said

Answer

I'd listen to your doctor.

Answer

Apps are going off of your last missed period. If the doctor did an ultrasound then he was able to see where the baby is it it’s development. For instance my due date according to my LMP was different than the ultrasound due date and the ultrasound due date turned out being the correct one. Hopefully this makes sense 😬 basically if baby is measuring to be 11 weeks according to the ultrasound than that’s most likely how they’ll decide your due date.

Could my doctor be wrong about my due date?

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