I just wanted to know how could I have possibly

Patient

Q: I just wanted to know how could I have possibly concieved on the 4th of January if I wasn't having sex at the very end of December. Is it possible based on the size of my baby that I could actually be father along but he's just small? My first ultrasound said I was 14weeks & that I conceived on the 1st & then the 2nd one said I was 13weeks & concieved on the 4th of January . When I found out the sex of the baby he measured at 18weeks.

Doctor

A:   Hello,
Thanks for the query to ATD for an opinion,

The fertilization generally occurs after the ovulation has occurred during the cycle i.e in a 30 day cycle day 14-16 is the ovulation time and any sexual activity from day 11-day 24 of the cycle can get you pregnant. So it shall depend on the last menstrual period of yours. Usually it is always day 18-day 24 which is seen as the date of conception.

If you are 18 weeks as on 10th MAY 2015 then your USG LMP should be 4th jan 2015 i.e. the date of conception. This is an ultrasonological estimation and there is always a 10 per cent discrepancy, hence the period os gestation is always counted from the last menstrual period in cases of women who always had good dates or who remember their dates well.

It would be helpful if you can communicate your last menstrual period and you date of last sexual activity, this shall help in deciphering the period of gestation of your conception in a more definitive manner.

I hope i have answered your query in detail,
Wishing you good health,
Regards

Comments / Follow Ups

Patient: Considering that my menstrual cycle was the second of December, & I spotted at the end of that month it threw the doctors for a loop. I used a pregnancy app based on my due date etc & the days they gave me for my last cycle was wrong.
Doctor: Hello,
With 2 dec as your lmp, the likely ovulation period would have been 16th dec onwards and fertile period maintained till 28-30 dec. you may have concieved in this period and the spotting would have been an implantation bleed . You experienced a delayed conception in this case. USG finding as i said can be discrepant by 10%.
regards

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