QuestionHi ! I have a question for you. I stopped taking birth control in April. Being on birth control, I had three "active" pill weeks and one "non active" pill week, making my cycle 28 days. My last period was April 25th. I should have resumed taking my birth control on May 2nd, but I did not. I found out I was pregnant on June 18. I went for a dating scan on July 8th that put me at 6 and a half weeks. I had another scan on August 27 that put me at 13 weeks and 5 days and another on October 11th making me 20 weeks and 1 day. From the first scan on my due date was determined to be February 27, 2011 and has not changed since. Doctor proposes that I conceived around June 6. I told him that I stopped taking birth control and did not have a period since April, so he did not even take that into consideration. My two main questions are this: 1. Eerily enough, the ultrasound calculates (with a conception date of June , 2010 6 and due date of February 27, 2011) that my last menstrual period was May 23rd. I know for sure I did not experience any bleeding and did not have a "period". When I count from April 25th, the start of my last known period, 28 days later is May 23rd. Can this be so? Would birth control not have messed up everything and thrown it out of wack? Counting 14 days after May 23rd is June exactly June 6th, the date that I would be expected to ovulate. I was not ovululating, as I was on birth control, but is it really possible to still be in synch with the pills? Can I still ovulate and not have had that actual period on May 23rd, which is the exacy day I would have gotten it if I was still on birth control?That is dead on. 2. My next question is if I had intercourse with a man on May 23rd and different man on June 5th, who would be the father to my baby? Is two weeks a sufficient time frame to be able to accurately give an answer? Thank you very very much!
AnswerIt's common for ovulation to be somewhat delayed after stopping the pill. So you stopped in late April but didn't ovulate until about June 6.
1. Ultrasound dating is based on the size of the fetus, and then calculates a last period 2 weeks prior to calculated conception. It doesn't matter when your actual last period was. If you're having 28 day cycles (not on the pill), then the dates should agree pretty close. Although the ultrasound could just date a pregnancy from conception, it's programmed to date from 2 weeks before conception, since we have traditionally dated pregnancies from last period. You didn't ovulate in May or you would have had a period 2 weeks later.
2. The ultrasound says your conception was June 6, and has an error no more than 7 days, meaning May 31 to June 13. So you could not have gotten pregnant from sex on May 23.
