Hi Cohen,

Thanks for your query.

The earliest period of time, ultrasound can pick up a confirmed live pregnancy is about 4 - 5 weeks from the last menstrual period. At 5 weeks, the fetal heart starts beating. Fetal sacs can be picked much earlier in a few weeks following fruitful intercourse which is a sign of pregnancy.

If you had had sex about a week ago and she has missed her period in the following week, the best test would be beta HCG testing.

One can become pregnant in a week after sex depending on the timing of fertilization. If the sex happened in the second half of her menstrual cycle and she missed her periods, pregnancy can be identified within once week of fertilization.

Confirmatory would be a beta HCG testing if Ultrasound is not confirmatory.

Hope this answers your query. Please get back if you need further information.

Regards

Dr Kiran

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