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Is conception possible while on Plan B contraception?

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Infertility Specialist
Practicing since : 2000
Answered : 3575 Questions
Good afternoon, I have a question, I’m constantly thinking about it, I am 23 weeks pregnant with my daughter. My due date is 04/10/13. I had my LMP in July right around the 15th until the 17th I had one day of normal bleeding and a day or two of pretty light bleeding/spotting, I was dieting pretty strictly and so stressed out about my upcoming wedding, I didn’t think the light period was odd. Because my husband is in the Military, There is only so many days we could have conceived. The first date would be: July 4th in the morning. I took Plan B the evening of the 5th, as I was trying to find a different birth control method at that time, and we did not use any. I was with my Husband again, July 18th through the 23rd, where conception could have happened any of those days. I got a positive pregnancy test August 20th 2013. Based off my LMP my OBGYN placed my due date: 04/21/13. I went in for my first ultra sound, at what we thought was 12 weeks 1 day. This was October 8th. At that visit they determined I was actually 13 weeks 5 days, and they changed my due date to: 04/10/13. I went in: 11/12/13. For my second ultrasound, where my due date did not change. I was told I conceived around: 07/20/13 which makes sense, but based off my LMP it means I would have had to ovulate early, and 11 days is a very large difference. I went in 12/11/13 for my third ultrasound at 22 weeks 6 days, My daughter was measuring at about 1 pound 3 ounces only slight below average for 23 weeks. Im nervous, because I know my first ultrasound wasnt done within the first 12 weeks, While my regular doctor and ultrasound tech told me, it really is very unlikely I conceived around the 4th of July, and that 14-16 days between possible conception dates is more than enough time to determine accurate gestational age, I saw another doctor yesterday (my regular doctor was in labor) and she told me at 13 weeks it could be off by more than 2 weeks. That made me lose sleep! Could my due date be around: 03/27/13?
Posted Fri, 3 Jan 2014 in General Health
Answered by Dr. Mahesh Koregol 1 hour later
Brief Answer: March Detailed Answer: Hi Your fear is right. You have conceived when you had sex on 3 or 4 July. You have not conceived july 19 to 23 sex it's earlier only. Hence I presume your plan B is failed. I hope your doubt is cleared. Regards Dr. Mahesh Koregol
Above answer was peer-reviewed by
Follow-up: Is conception possible while on Plan B contraception? 8 minutes later
I dont understand, as a 13 week ultrasound should only be off by about 7 days?
Answered by Dr. Mahesh Koregol 4 minutes later
Brief Answer: margin of error Detailed Answer: Hi Second trimester ultrasound is not dating ultrasound. Early pregnancy ultrasound before 8 weeks is best to determine dates. Second trimester ultrasound has margin of error plus or minus 10 days. Hence you can't rely it for accurate dating. Regards
Above answer was peer-reviewed by
Follow-up: Is conception possible while on Plan B contraception? 10 minutes later
I deinately uderstand that the margin of error is within ten days, but doesnt that mean my due date would be near the first of april? Making my conception date around july 8th or 9th? I never had sex around that time?
Answered by Dr. Mahesh Koregol 5 minutes later
Brief Answer: XXXXXXX cycle Detailed Answer: Hi The date needs to be calculated based on cycle you has in XXXXXXX Because to conceive on 3 or4 july conception the cycle would have been started in after XXXXXXX 15. Hence add 9 weeks plus 7 days to XXXXXXX cycle which gives you EDD. Regards
Above answer was peer-reviewed by
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