Jessica Simpson and her husband Eric Johnson ''always practice'' making babies.

The 37-year-old star and Eric, 38, already have daughter Maxwell, five, and son Ace, four - but Jessica has joked about their sex life since becoming parents, admitting the additional responsibility hasn't slowed them down at all.

Of her young family, Jessica shared: ''My daughter is about to turn six, May 1st is her birthday, and my son is going to turn five on June 30th and it's just like, 'Wait, so this is no longer toddler, this is full-on kid.'

''My daughter [already] thinks she's a teenager. My son at least wants to be a baby still.''

Jessica and the former American football star tied the knot in 2014.

And while the loved-up couple have spoken about expanding their family, she ''don't really know'' whether it will happen.

Speaking to Entertainment Tonight, Jessica quipped: ''We always practice. But it would definitely have to be a miracle.''

The blonde beauty also revealed how she and her husband have managed to maintain their romance, admitting alone time is key to their happiness.

She said: ''Today, we got to go on this trip without the kids, [and usually] we don't go places without the kids.''

Jessica added that by taking the trip on their own, they managed to give each other ''all of the attention''.

Meanwhile, Jessica previously ruled out the prospect of having any more kids.

During her appearance on 'The Ellen DeGeneres Show' last year, she denied rumours she was pregnant and revealed she'd taken measures to stop it from happening.

Jessica - who was previously married to actor Nick Lachey - said: ''I'm not pregnant. We got an IUD, nothing's gonna get in that uterus. I have two beautiful children and I'm not having a third.''