First of all b'Shaah Tova, may everything progress smoothly to a healthy baby.
The Gemara writes that a woman is only considered to have ceased seeing her period after 3 months of pregnancy, and only then may she desist from observing her regular vestos. HaRav Moshe Feinstein zatzal observes in Igros Moshe that today nearly all women stop seeing their monthly period immediately upon conception, and based on this he writes that the Halacha has changed and a woman may ignore her cycle as soon as a reliable test has confirmed pregnancy. While this seems to be a very logical conclusion, the overwhelming majority of Poskim do not concur with Reb Moshe's leniency and if fact in a later teshuva Reb Moshe himself seems to retract this kula.
L'Halacha one should follow the stringent, majority opinion on the 30th day during the actual time period of the previous period, whether day or night. However, the other half of the day and the 31st day are only chumros in any event, and one may be lenient when there is a confirmed pregnancy.