Two of the leading Sprint Cup Series drivers are celebrating first-time fatherhood this week, after the arrival of a baby boy for Kyle Busch and his wife Samantha, and a daughter for Brad Keselowski and girlfriend Paige White.

Brexton Locke Busch was born on Monday evening at 9.45pm, weighing in at 7lbs 10oz and 21 inches. The proud father made the announcement on Twitter, and added that "Mom n baby doing great!"

Busch had been for more of the pregnancy that he had been expecting after breaking his left and foot in a racing accident at Dayton in February.

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"It stinks to be sitting on the sideline, but to be honest with you, the silver lining is to be home, to be with Samantha and to prep for our son coming. I think that's been the most fun," Busch said in April.

However he has since made his return to competition last weekend in the All-Star Race at Charlotte Motor Speedway, and will be around the house rather less in the coming months as he seeks to battle his way back into Sprint Cup contention.

Busch recently turned 30, and his wife Samantha will be celebrating her 29th birthday on June 1. They had made a public announcement that they were expecting their first child last October.

By contrast, Keselowski left it late to reveal that he and his girlfriend were on the same journey, the 2012 Cup champion only revealing in February that he and Paige were expecting a girl around the same time.

The delivery finally took place on Tuesday night, just 24 hours after the Busch's baby boy made his d?but appearance. Keselowski and White have yet to announce a name for the new addition to their family.

Keselowski admitted that he and his team hadn't made any backup plans in case the call from the hospital came while Keselowski was meant to be competing in either the All-Star Race or this upcoming weekend's Coka-Cola 600 at Charlotte Motor Speedway, the home venue for NASCAR and most of it teams and drivers including both Busch and Keselowski.

"Fingers crossed. We'll see how it all plays out, but I'm looking forward to it very much," said Keselowski earlier this month. "As far as contingency plans, we haven't really made any because we're very, very fortunate that everything at this time looks to fall directly in line with the race weeks in Charlotte, which is where we live,"

Penalties announced for Iowa and Charlotte

NASCAR has announced penalties arising from last weekend's Xfinity Series race at Iowa Speedway, and the Camping World Truck Series race at Charlotte Motor Speedway.

In the former, the JD Motorsports team has been penalised after a lead weight ballast detached from Ross Chastain's #4 car and flew off into the windshield of Jamie Dick's car during first practice on Saturday morning. The weight went on to hit Dick on the head, but fortunately he was uninjured.

The infraction is breach of Rule 20.17.2.1 of the series regulations requiring all ballast to be affixed properly. It constitutes a P3 level penalty and earns crew chief Gary Cogswell a $15,000 fine NASCAR probation through to the end of the year. The #4 car chief Charles Kent has also been placed on NASCAR probation through Dec. 31.

In the Truck Series, race winner Kasey Kahne's #00 entry failed post-race technical inspection for being too low in the front on both sides and too high on the right rear, a breach of 20.17.3.3.2. This is a P2 penalty meaning that crew chief Joe Shear Jr. has been fined $6,000 and placed on NASCAR probation for the rest of the year, while car owner Dale Earnhardt Jr. has been docked 10 NASCAR Camping World Truck Series championship owner points.

There was also written warning but no penalty for Hendrick Motorsports after Jimmie Johnson's #48 crew were suspected of infractions during the NASCAR Sprint All-Star Race on Saturday.

The team was being looked at for making an unapproved adjustment of a body panel during a pit stop late in Saturday night's annual exhibition event, where it appeared that crew members attempted to pull out the car's side 'skirts' to improve downforce and grip late in the race.

That was a popular practice during the 2014 Sprint Cup season, but was banned over the off-season with NASCAR using its new pit road video monitoring system to ensure that teams did not carry out the practice this season.

Crew chief Chad Knaus explained on Monday that the team had needed to make an allowed repair to the #48's right hand side bodywork after early contact with the wall, and also needed to make adjustments after contact with Joey Logano.

If HMS had been deemed to have made side skirt adjustments in the All-Star Race, it's unclear what sanctions NASAR could have actually handed down. The official rule is that a team found to be making those sort of disallowed changes during the race would be required to come back in and correct the infringement. However there is no post-race penalty specified, which is even harder to address in the All-Star Race where no Cup championship points are at stake.

"It's not a points race, but certainly we know how much it means to win that race, so hopefully we don't have to make a call on this, but we would maintain the rule book throughout the race," said Robin Pemberton, NASCAR senior vice president of competition and racing development on Monday.