New York - Serena Williams is about to have a baby, Victoria Azarenka will stay home with her baby and the US Open women's field is pregnant with suspense over who might win. 

A wide-open array of contenders for the world number one ranking and the last Grand Slam title of the year promise to make the Flushing Meadows fortnight that starts Monday a thriller even without two of the game's top stars. 

Williams, who won her 23rd Grand Slam title at the Australian Open, announced in April she was pregnant and would miss the rest of the year. 

Two-time Australian Open winner Azarenka revealed she is in a custody fight over her baby son, who cannot leave California, and thus will stay with him. 

Former world number one Maria Sharapova, a five-time Grand Slam champion, will play as a wildcard in her first major tournament since a 15-month doping ban after testing positive for meldonium at the 2016 Australian Open. 

And while the Russian's return has been hit by forearm and thigh injuries, she remains a threat wherever she lands in the draw. 

Czech world number one Karolina Pliskova, Romanian world number two Simona Halep, Wimbledon champion and world number three Garbine Muguruza, Ukraine's fourth-ranked Elina Svitolina, Denmark's fifth-ranked Caroline Wozniacki and the defending champion, sixth-ranked German Angelique Kerber, are among the trophy favourites on the New York hard-courts. 

Evergeen Venus Williams, the 37-year-old American who has won seven Grand Slam titles and was runner-up this year at Wimbledon and the Australian Open, is ranked ninth and a dangerous foe for all. 

Muguruza has made herself an oddsmaker's darling after taking last year's French Open, last month's Wimbledon crown and last week's Cincinnati title in the last major US Open tune-up. 

But she hasn't gone past the second round in four tries at New York. 

"I'm looking forward to be there and feel I can improve what happened the past years, because I feel like I never really found my (rhythm)," Muguruza said. 

"I want to change that. I want to find the recipe maybe this year, maybe that I have a little bit more confidence. 

"The most important part is to recover, to be fresh because it takes a lot of energy, and then getting used to New York vibe again, because it's special." 

Pliskova has taken titles at Brisbane, Doha and Eastbourne this year but has never won a Grand Slam, although she reached her only Grand Slam final last year at New York. 

"The energy of the city is huge. Obviously love to be coming back there, especially after the fantastic last year." 

An early Cincinnati exit tumbled Kerber down the rankings race, but the 2016 US and Australian Open champion is feeling the same drive she did a year ago. 

"I'm thinking that my fighting spirit is back and I'm feeling that it's getting better and better," Kerber said. "Going, for sure, with good memories to New York." 

Halep isn't after a 6-1, 6-0 drubbing by Muguruza in the Cincinnati final, her third and by far worst loss of the year with the world number one ranking just a win away. 

But that didn't dim her hopes of claiming a first Slam title at the US Open. 

"I will go to New York and I will be with the confidence up," Halep said. "I played really good few months. So I don't have negatives to take." 

Svitolina, the youngest in the favoured pack at 22, has won titles this year at Toronto, Rome, Dubai, Istanbul and Taipei City and matched her best Grand Slam showing with a French Open quarter-final run. 

Wozniacki, the 2014 US Open runner-up and three times a semi-finalist, has lost six finals this year since taking her last title in Hong Kong last year.