Yahoo! CEO Marissa Mayer announced on tumblr.com that she is pregnant with twins, but plans to approach her pregnancy and delivery by taking “limited time away” and “working throughout.” Mayer, 40, said her identical twin girls will likely be born in December. She and her husband Zachary Bogue already have a son.

The 40 year-old Ms. Mayer has been in a major three year turn-around effort as CEO of Yahoo!. Previously, she was a long-time executive, usability leader, and key spokesperson for Google. Fortune‍  ranks Mayer as the 16th most powerful businesswoman in the world.

According to the Hollywood Reporter: “Marissa Mayer had to know that whatever length of maternity leave she’d take after giving birth to twin girls would be the subject of massive controversy.” Mayer was already six months pregnant with her son, Macallister Bogue, when she was named CEO in 2012.

There was considerable shareholder concern in 2012 about her focus, but she announced she would only take two weeks of maternity leave and did. Now that she is doing it again, there are no shareholder concerns. But Mayer has been denounced as a bad role model for putting other women under pressure to return too quickly to work after delivery.

Since Mayer joined the company in near-collapse, she has hired more engineers, strived to revive flagging sales and ordered a string of top management departures. Although shareholders give her credit for preventing the company’s demise, she still hasn’t convinced enough consumers to make Yahoo! a daily destination, especially on mobile. According to ComScore, eight of the top 10 smartphone apps in the U.S. are owned by either Google or Facebook. Yahoo did not have an app in the top 15.

Mayer launched her biggest initiative in July, the $32 billion spin-off of Alibaba shares into a separately traded-company that may be worth more to shareholders than the current value of Yahoo shares.

The deal was roaring ahead until the IRS questioned the transaction after Yahoo!’s July 17 SEC filing. The spinoff is to be called Aabaco Holdings is expected to consist of 384 million shares of Alibaba, representing a 15 percent stake in Jack Ma’s Chinese Internet firm; and Yahoo! Small Business, which services Internet merchants. The inclusion of the “Small Business” was meant to strengthen Yahoo’s case that the transaction should be considered a tax-free spinoff rather than a stock sale subject to capital gains taxes. If the IRS rules the deal is a sale, Yahoo would owe a 40 percent tax, or $12.8 billion in tax.

The company indicated that the IRS accepted the transaction as a tax-free spin-off in January, but the new SEC filing acknowledges that the government tax agency is “reconsidering its ruling policy.” Mayer can still move ahead on the spinoff, even if the IRS doesn’t stipulate it will be tax-free. But it is shareholders that are at risk for the tax.

Mayer already has a tough situation juggling all the balls at Yahoo!. But attacks in the blogosphere have called her short maternity leave “a bad precedent for Yahoo’s lower-level employees, mothers and fathers, who do not have the job flexibility and cannot afford the extensive social support and backup systems that Mayer and her husband will be able to construct,” according to CNN blogger Stephanie Coontz. Other bloggers have been critical as well.

Only 13 percent of full time U.S. workers currently have access to paid family leave, according to the Bureau of Labor Statistics. As someone who is sympathetic to the needs of her employees, Mayer doubled Yahoo!’s paid maternity leave from eight to sixteen weeks in 2012.

Mayer currently manages a $62 billion company with 11,400 employees. She earned $42 million a year as Yahoo’s CEO and by all accounts has done a good job. Her ability to demonstrate that a woman can have a family while managing a major U.S. multi-national corporation should be applauded, not denounced.