Dear Lance,
With history of an unprotected sex by a woman in reproductory age groups always carries a possibility of
pregnancy. Hence, the condition should be evaluated on its merits.
The chances of conception are highest if the intercourse was on the day of ovulation, and has fair amount of possibility of pregnancy in fertile window.
Ovulation usually happens 14 days prior to the next expected menses in a woman having regular
menstruation. Considering the egg's life of 24 hours and that the sperms are active for 72 hours, a period of about one week around the day of ovulation is fertile window.
Your partner's expected date of menses being 31, the day of ovulation would be 17th and the fertile window would be from 13th to 21st. Now you can figure out what are the possibilities of pregnancy.
There is no use of guessing for the possibility of pregnancy unless she has missed her period. Missing a period is the first cardinal symptom of pregnancy. The other symptoms like
nausea &
vomiting with pica, frequency of urination, breast changes like engorgement with tenderness, dark discolouration of nipples &
areola with areolar widening, appearance of Montgomery's tubercles under the areola and secretions from the nipples - all start appearing about one week after the missed period.
If due date of her menses is yet ahead, you may wait to see whether she really misses her period. If she misses, please wait for at least one week before you perform home pregnancy test on her urine as immediately within first week of missed period, the chances of false negative tests are very high with these tests. Alternatively, you may opt for
Beta hCG test which is very reliable even few days before missing a period. I feel, going for Beta hCG test 10 days after the incidence of
unprotected intercourse would be the best advice for you.
I hope this helps you in this dilemma.
Dr. Nishikant Shrotri