Tubal Ligation & Potential Ectopic Pregnancy: What to Do?

Question
age 33
Son 5
Daughter 2
Son 18 months

I had a tubaligation this last summer.  I am fairly certain I am pregnant.  I have not yet missed a period and know a pregnancy test would not give an acurate reading if I am.  I've been pregnant 3 times each time I knew a month to 6 weeks before the tests showed positive.  I am concerned about ectopic pregnancy.  HOw soon would an ultrasoud show all is well?  And is there anything I can do to prevent the embryo from planted itself is the fallopian tube?  
Thank you!

Answer
Without knowing the first day of your last period, I cannot tell you when a pregnancy test will show a positive result. However, if it has been seven days since you were supposed to get your period, a pregnancy test will be accurage. A pregnancy test will not show a positive result until 14-21 days after conception (ovulation). Usually, after fertilization of the ovum, the fertilized egg travels back towards the uterus where it will implant in the endometrium. If it gets stuck in the tube (for whatever reason), it can grow there and becomes an ectopic (tubal) pregnancy.  A sonogram will not show much of anything until 5-6 weeks from the first day of your last period, and we can diagnose an ectopic pregnancy by the absence of a gestational sac in the uterus and the presence of a mass in one of the adnexa. In addition, a pregnancy test will be positive. I would suggest that if you miss your next period, you wait an additional seven days and then take a blood pregnancy test (Beta HCG) twice, 48 hours apart. If there is a doubling of the results in 48 hours, it indicates a viable pregnancy. If it drops in 48 hours, it inidicates a miscarriage. If it stays the same, it may indicate an ectopic pregnancy. However, it is highly unlikely that you are pregnant (intrauterine or ectopic) if you had a tubal ligation at your last pregnancy, unless it was not performed correctly.