WASHINGTON — In the history of the nation, only 10 members of Congress have given birth while in office and Sen. Tammy Duckworth, D-Ill., is one of them.

Soon Duckworth will be in a class by herself.

Duckworth told me she is expecting her second child, another girl, in late April, a few weeks after she turns 50. The birth will make Duckworth the nation’s first senator to have a baby while serving in the chamber.

Sen. Dick Durbin D-Ill., said in a statement, “I am proud to have her as my Illinois colleague and prouder still that she will make history by being the first U.S. Senator to have a baby while in office. I couldn’t be happier for her.”

The other congressional births have all come while the female lawmakers were serving in the House.

“I feel great,” said Duckworth, a little over six months pregnant.

We talked in Duckworth’s Hart Building Senate office, a few days after she returned from a five-day official trip to Japan and South Korea.

It was the longest she has been away from Abigail, she said. Her daughter was born Nov. 18, 2014, when Duckworth was 47 and a member of the House.

Many of you are familiar with Duckworth’s story. She is a retired lieutenant colonel who served a total of 23 years in the Illinois Army National Guard. Duckworth lost her legs and shattered her right arm when her Black Hawk helicopter was shot down in Iraq on Nov. 12, 2004.

She initially won the Illinois’ 8th Congressional District seat in November 2012.

Duckworth and her husband, Bryan Bowlsbey, tried various fertilization methods over a period of years before Abigail O’kalani Bowlsbey was conceived through a form of in vitro fertilization.

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After Abigail’s cesarean birth, Duckworth had to wait 18 months to try again. “I’ve had multiple IVF cycles and a miscarriage trying to conceive again, so we’re very grateful,” she said.

The miscarriage occurred in 2016 during her Senate campaign, Duckworth revealed.

Duckworth became the second female U.S. senator elected from the Illinois when she was sworn in on Jan. 3, 2017.

Duckworth decided to run for the Senate while on maternity leave with Abigail. “As tough as it’s been to juggle motherhood and the demands of being in the House and now the Senate, it’s made me more committed to doing this job,” she said.

Getting pregnant a second time was, she said, “a struggle.” Her fertility specialist for both pregnancies is Dr. Edmond Confino at Northwestern’s Feinberg School of Medicine.

There are now 22 women in the Senate, a record number. In this current crop, the mothers among them had their kids before entering Congress, with the exceptions Duckworth and Sen. Kirsten Gillibrand, D-N.Y., who had one of her two sons while in the House.

Becoming a mother — one who commutes between Washington and Hoffman Estates — influenced Duckworth’s legislative agenda.

“I have a better understanding in a way that I didn’t have,” Duckworth said. Before her baby, Duckworth was familiar with issues facing nursing mothers. Just how tough it could be was underscored when “I was the one who was trying to pump breast milk in airports.”

Since Abigail was born, Duckworth has authored measures to make sure major airports offer places for breastfeeding mothers to pump milk; the military creates a uniform policy for giving personnel time to bond with their newborn and adopted babies; and to make sure student parents have on-campus child care.

She also is a sponsor or co-sponsor of bills dealing with affordable child care, paid parental leave and other infant and maternal health issues.

Duckworth’s mother, who lives with her, is key to helping the senator balance work and family life. Her mom travels back and forth to Illinois with her daughter and granddaughter.

Even with her mom and a nanny for backup, Duckworth said there is “the constant feeling of guilt when I’m not with her.”

Born in Thailand, Duckworth wants Abigail to speak Thai, so she hired an au pair who is certified as a teacher in Thailand.

“My mom and nanny speak to her in Thai and I speak to her in a combination of Thai and English,” Duckworth said.

Duckworth related that Abigail once asked her, “’Mommy can’t you stay home from work today and play with me?’ . . . What do I say to a 2-year-old? ‘No, Mommy has to go make sure our Department of Defense has the budget it needs.'”

Does Abigail know what a senator does?

“No,” Duckworth said, adding, “the cutest thing, every time she sees a picture of the U.S. Capitol, even if it’s on a dollar bill, she says ‘Mommy’s office.’ And I have to say, ‘Well, it’s not quite Mommy’s office, but in a way you’re right.’ ”

Three of the 10 House women went on to serve in the Senate: Duckworth, Kirsten Gillibrand and Blanche Lambert Lincoln.

Duckworth will become the first sitting senator to give birth.

Rep. Cathy McMorris Rodgers gave birth to three children while in Congress, the most of any sitting lawmaker.

The Women Who Gave Birth While Serving in Congress

• Rep. Yvonne Brathwaite Burke, D-Calif.
• Rep. Susan Molinari, R-N.Y.
• Rep. Blanche Lambert Lincoln, D-Ark.
• Rep. Enid Greene Waldholtz, R-Utah
• Rep. Linda Sanchez, D-Calif.
• Rep. Stephanie Herseth Sandlin, D-S.D.
• Rep. Cathy McMorris Rodgers, R-Wash.
• Rep. Kirsten Gillibrand, D-N.Y.
• Rep. Jaime Herrera Beutler, R-Wash.
• Rep. Tammy Duckworth, D-Ill.

FOOTNOTE: Here is the House of Representatives official list of “Familial Connections of Women Representatives and Senators in Congress.”