Serena Williams still maintains fears over whether she will return to the same player that won 23 Grand Slam titles following her pregnancy.

The American won the Australian Open last year after defeating her sister Venus in the final and in the process, became the No. 1 ranked female player in the world for the seventh time in her illustrious career.

However, injury and later pregnancy resulted in her taking time away from the sport as she would later give birth to her daughter Alexis Olympia in September.

Tennis fans were given a glimpse into Williams' life right from the revelation of her pregnancy in her new five-part HBO documentary series "Being Serena" as she spoke about her role as a first-time mother.

"Becoming a mom, I definitely feel the pressure, and I feel a little anxiety," Williams said in the first part of the series that released Wednesday, as quoted on CNN. "Am I going to be a good mom, a strict mom, not strict enough?"

"I don't really know, so that anxiety has turned into nervousness and fear. ... It's the same attitude I have in tennis," she said.

Williams would return to competitive action for the first time in 14 months as she featured in the BNP Paribas Open in Indian Wells, California in March. The 36-year-old won her first two matches but exited in the third round after losing to Venus.

She would then lose her opening round match against Naomi Osaka at the Miami Open as there still seems to be rust that requires shaking off for the 23-time Grand Slam champion.

But despite every player needing time to get back to their best after a long layoff, Williams also spoke of her fear that she may not become the best tennis player in the world again.

"There's no escaping the fear -- the fear that I might not come back as strong as I was, the fear that I can't be both the best mother and the best tennis player in the world," she added. "I guess my only choice is to live and find out."

Williams is set to feature during the clay swing but will not take part in the Madrid Open that commences from May 7-13 after withdrawing from the event. It was expected that she may not feature in the capital of Spain either but she recently told the New York Times that she will "definitely" be taking part in the Rome Masters and the French Open that follow afterward.

The first of five parts of "Being Serena" can be viewed on HBO.com. The remaining parts will air every Wednesday on HBO at 10:00 p.m. (ET/PT).

"It documents my pregnancy, the extremely difficult time I had in the delivery room and all of the emotions that came with it," Williams said of the documentary. "It also covers my wedding, which was so exciting and fun. It was honestly the best day of my life. And then of course, it shows my comeback, because I'm coming back, I'm playing tennis, I'm back on the court, and it's so invigorating."