But there is no way to precisely date the beginning of a pregnancy from an ultrasound from the 22nd or 24th week of pregnancy
. By now, the margin for error in
dating would be a couple of weeks
plus or minus. All those later ultrasounds can tell you, given the differences in growth rates in babies, she could have conceived any time in late June through late July.
Did she get an early ultrasound, such as in her 7th or 8th week?