BabyT,
It depends on when you ovulate lor. Let's say my cycle is 29 days and I ovulate in the middle of the cycle on CD14 (+ or - CD14 is quite the norm for most people with regular and not exceedingly long cycles), then by the time I am 4 weeks past ovulation, I'll be ~6 weeks into pregnancy based on my last menses. But if I ovulate a week late, say on CD21 instead of CD14, then the 4 weeks past ovulation will be ~7 weeks into pregnancy based on my last menses. Get what I mean? But in both cases, the foetus is really only 4weeks old cos age is really dependant on date of conception not LMP. So using LMP to calculate EDD is not always accurate. Need to base on the length/size of the foetus to determine more accurately how far into the pregnancy you are. Unless of cos, you are able to tell the gynae your date of ovulation. Not everyone who gets pregnant use ovulation strips or monitor BBT/Cervical Mucus.
My O date is 13/12/2009 (I check BBT). My LMP is 28/11/2009. Based on LMP, I'm 5wk 6day into the pregnancy. Conception should take place on 13-15/12/2009 (egg lives for up to 48-72hr thereabouts). So current fetal age should be 3wk 5day old (I must qualify - if there's really something growing). When fetal age is thereabouts 4wk, should be able to detect heartbeat.
Yes, utrogestan is to support the pregnancy and "strengthen the womb".