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Pregnant. How to calculate the exact pregnancy week by week? - Online Doctor Chats

Date : 10-Jun-2013
User rating for this question
Very Good Posted in: Pregnancy
Answered by

General & Family Physician
Practicing since : 2009
Answered : 983 Questions
User:My wife is pregnant and her last period was on the 5th of December 2012. So as per LMP she is supposed to be 7 weeks and 4 days pregnant but the latest ultrasound scan tells us that she is only 6 weeks and 4 days (+/- 1 week) pregnant. Please explain why there is a difference and how many weeks is she exactly pregnant?
Doctor:Good morning
User:Hello doctor
User:good morning
Doctor:How can I help you?
User:can you read my question?
Doctor:Yes. I am going through the question.
Doctor:I can guide you regarding this.
Doctor:LMP is calculated from the first day of last menstrual period.
Doctor:That is designed for a rough calculation of the pregnancy.
Doctor:But in practicality, the fertilization occurs maybe 10-15 days after the LMP.
Doctor:So, when a sonography is done, there is always a difference of 1-2 weeks.
User:thanks for that
Doctor:have you followed my explanation?
User:in fact we had a follicular monitoring done after LMP
User:thrice on 13th 15th and 17th day after LMP
User:so we knew exactly when ovulation had happened and final rupture
User:so in our case the US report should match the LMP date
User:the injection for ovulation was given on the 15th day after LMP and rupture was confirmed on the 17th day
User:since pregnancy is usually measure with respect to the menstrual cycle
User:and we had an exact 14 days cycle
User:i was expecting the date to match
Doctor:Ok. Let me explain in more detail.
Doctor:How often and regular was your wife's menstrual periods?
User:she had irregular periods
User:and the frequency was roughly once in 2 months
User:but we visited the gynaec
User:who prescribed siphene
User:and for 2 cycles the periods were on time
User:nearly 28-31 days
User:and in both these cycles we were trying for a baby
User:and it dint happen in the 1st cycle
User:but both the times
User:we were monitoring the follicle
Doctor:So her cycle was around 28-30 days.
User:more or less, yes
Doctor:Not 15 days.
User:more or less, yes
Doctor:The ovulation takes place around 14 days prior to the period.
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