How strong does a baby kick in the womb?: New study finds it's powerful

— -- ABC News chief meteorologist Ginger Zee is expecting her second child in February.

While Zee, 37, wakes up early to report on "Good Morning America," in recent weeks she has been up even earlier for a different reason: Her baby's powerful kicks inside the womb.

"The other night he kicked me so hard I woke up," Zee said. "I have not gotten used to it and he doesn’t only react to food. He kicks when I’m hungry. He kicks when I’ve eaten protein, sugar, anything."

Zee is not waking up in the night due to a mild kick. The baby kicks keeping Zee and other expectant women up at night can pack quite a punch, according to a new study.

A fetal kick at 25 weeks could exert an 8-pound force, while a kick at 30 weeks produces a nearly 11-pound force, according to the study, which evaluated fetal movements through different phases of pregnancy.

For comparison,the average force of a hammer hitting a nail is 100 pounds. The force of a karate punch can be anywhere from 400 to 1,000 pounds.

"This kid is a dancer," said Zee, whose first child, Adrian, was breach so not as active in the womb.

"He is most active in the evening. That’s when he likes to push his butt and back out my left rib cage and his feet out my right, stretching me apart," she said. "It's wild."

While the kicks may be uncomfortable for the mom, there is no danger to the mother or the baby from these movements, doctors say.

Zee, who is due just two weeks, could feel a reprieve from her baby's kicks very soon.

As the fetus grows inside the mother's womb, the force of its kick diminishes, the study found. At 35 weeks, it starts to go down to less than four pounds of force.

Researchers at Imperial College London examined MRI scans of pregnant women for the study, published this week in the Journal of the Royal Society Interface.

They used complex formulas to calculate the force that would be delivered by the movements of the fetus. They also noticed the force of the kick increased between weeks 20 to 30 of pregnancy before starting to decrease again.

Understanding fetal movements.

A baby's kicks, known as fetal movements, are thought to be good for the baby as they contribute to the development of their bones and muscles.

Taken together with other studies, the researchers' new findings can help better categorize fetal movements as women progress through pregnancy as sudden changes in fetal movements can be a cause for concern.

Zee said she actually asked her doctor if her baby was getting enough sleep in the womb because he is "always kicking and not resting."

Like many moms though, Zee said she finds the kicks reassuring, if also uncomfortable.

"This child never stops moving, which is a good and healthy sign so I’m grateful," she said.

Here are 4 more things to know about baby's kicks inside the womb:

1. The first movement: Pregnant woman can first feel movement of the baby in the second trimester, usually around 16 to 20 weeks. Movement can also be picked up much sooner -- as early as seven weeks -- with an ultrasound.

2. Movement peaks at night: Fetal movement typically increases as the day goes on and peaks late at night.

3. Counting kicks: Pregnant women should have a discussion with their doctor about normal fetal movements, changing patterns as the fetus develops and what things to look out for.

4. Decreased movement: Pregnant women should contact their doctor right away if they have any concerns about decreased movement of their baby. While it may be a normal variation, it is important to monitor this closely and keep the doctor in the loop.