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Dr. Norm S.
Dr. Norm S., Doctor
Category: Medical
Satisfied Customers: 11287
Experience:  Over 30 years of experience in OB/GYN practice.
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Myself and my girlfriend had unprotected sex for the first

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Myself and my girlfriend had unprotected sex for the first time on 13th January this year.
On Saturday 9th February she told me she was pregnant.
We visited the midwife Thursday 7th February and she asked my girlfriend when her last period was. She told her it was the 28th December 2012 and lasted 5 days.
The midwife said my girlfriend was 9 to 10 weeks pregnant, it was at that point that I interrupted and said that was impossible as we knew the exact date we had sex as it was our first time. She could only be 7.5 weeks pregnant.
The 12 week scan was booked for 4th April. When we got home we received a phone call to say the scan date had been changed, it was now 14th March.
I know something isn't adding up right I just don't know enough about pregnancy to put it all together.
Welcome to
Was an ultrasound scan done when you visited the midwife? Thank you.
Customer: replied 5 years ago.

no. the ultrasound will be done tomorrow. do you have any advice with regards XXXXX XXXXX I should be looking out for.


I have told you when we had sex and the date is rock solid. what should I expect at the scan tomorrow?



I'm confused about one thing, and then I will be able to answer your question.
You say that your girlfriend told you she was pregnant on February 9, and that the two of you saw the midwife on February 7 (2 days earlier). Is that correct?
Customer: replied 5 years ago.

Sorry, March 7th was when we saw the midwife.

Thank you. That clears things up.
Assuming that conception occurred on 13 January, on 7 March your girlfriend would have been 9 1/2 weeks pregnant. I think the confusion is because by tradition, we date pregnancies from last period, so that when we say someone is 9 weeks pregnant, that actually means that conception occurred 7 weeks ago, since we assume that the last period occurred 2 weeks before conception. This way of dating began before ultrasounds were available, when the best way to date a pregnancy was usually from last period. So with conception on 13 January, your girlfriend would have a due date of about 6 October, and would be 9 1/2 weeks on 7 March. On 14 March she will be 10 1/2 weeks pregnant (8 1/2 weeks from conception). As long as the scan comes within 4-7 days of that date, it will confirm the dates (since no scan is perfectly accurate). I hope that's helpful.
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