Garcia will next take on Ukrainian qualifier Marta Kostyuk who defeated Antonia Lottner.
Mirza and her husband, former Pakistan cricket captain Shoaib Malik, posted a picture on their Twitter accounts of a baby vest and a feeding bottle between two T-shirts bearing their names.
The 21-year-old displaced Marin Cilic after his progress to the Monte Carlo Masters semifinals.
The Spaniard's 31st Masters title is also an outright record, pulling him out of a tie with Novak Djokovic.
France's world number 122 Pauline Parmentier must beat 13th-ranked Madison Keys to deny the US a place in November's final.
The Czechs will meet France or the USA in the November final.
Miyu Kato and Makoto Ninomiya won the deciding doubles to end British hopes of breaking back into the Fed Cup's top 16 for the first time since 1993.
Australia were last in the elite group of the Fed Cup in 2015, while the Netherlands were trying to prolong their three-year stay in the top tier.
Nadal reached his 12th final in Monte Carlo earlier Saturday by seeing off Grigor Dimitrov
Goerges will now be under pressure to win Sunday's opening rubber against Pliskova to save the Germans from defeat in their home semi.
The 31-year-old, who needs to win the title to retain the number one ranking ahead of Roger Federer, will face either Kei Nishikori or Alexander Zverev in Sunday's final.
The world number four is looking for his third Masters title and hoping to bounce back from the disappointment of his final loss to John Isner in Miami.
The Spaniard will face Grigor Dimitrov in the last four on Saturday.
The 26-year-old Bulgarian booked a last-four clash with either defending champion Rafael Nadal or Austrian Dominic Thiem.
Matches will be available to watch live and on demand for members of Amazon Prime Video, its internet video service.