How accurate are dating scans?
Patient: Hi I need to know how acurate 3 dating scans are as a measure of paternity. I know I need to do a dna test but all three scans perfromed at 12, 16 and 20 weeks have provided the same due date and therefore the same conception date and I was with the suppossed father that day. Can you help me? Doctor: Hello, and I hope I can help you today.Estimating your date of conception is only really possible for women who have a 28 day menstrual cycle. By convention, the computer programs that are used to calculate your due date are working from an assumption that a woman has a 28 day cycle, and that conception took place exactly 2 weeks after your last period. If your cycle is longer or shorter, your ovulation could have taken place on a different day than what is estimated.So really just depends on whether you were with your second partner during your fertile window, which really can start 7 to 10 days after the first day of your last menstrual period and continue until a week before your next menstrual period is due.So depending upon how close and timing your sexual encounter with your second partner was, will determine how likely it is for him to be the father. If the margin either way is only a matter of a few days, you really will need a DNA test to accurately predict the paternity of your child.I hope that I was able to adequately answer your question today, and that my advice was helpful.Best wishes for the rest of the pregnancy,Dr. Brown