Need advice - is this exercise safe?

sounds like a butterfly crunch

What you experienced was your lower abdominal muscles contracting to provide support for your torso as you lifted your head and shoulders to see your child.

There are many exercises out there "designed" to work the lower abdominal area. You should be able to search the internet for "lower abdominal exercise" and find many.

Please be cautious with lower abdominal exercise though. Your lower back needs to be flat against the floor or exercise bench you are using. Tilting your pelvis forward will achieve this (you will feel your abs contracting when this happens). Pelvic tilt or positioning is key to determining whether the abdominal muscles are working or not.

The functions of abdominal muscles are stabilization of the torso, lateral flexion (bending sideways), spinal rotation (twisting), and spinal flexion (bending forward). Depending on your school of though, another action is spinal extension (bending backwards). When these muscles act, the SPINAL COLUMN is what is moving or pivoting.

Don't confuse abdominal exercise with movements the cause hip flexion (bending forward at the hip with a "straight" back). The muscle group which is responsible for hip flexion are collectively and generically called the hip flexors.

It is very easy to confuse spinal flexion (abs working) with hip flexion (hip flexors working) because the abs are working as the major support group for the torso. The hip flexor muscles, also called the iliopsoas muscles, originate (start) from the mid to lower lumbar vertebral bodies and inner side of the the ilium (hip bone) travel through the pelvis and inserts (stops) to a spot on the inner upper area of the humerus (thigh bone). It's primary function is hip flexion and is also involved with rotation of the hip joint and assists with spinal extension. While many identify hip flexion with bending forward at the hip, these muscles act to pull the leg towards the abdomen.

In reference to this thread, two different actions are taking place. The first is the action of the hip flexors to pull the leg towards the abdomen. The other is the stabilization of the torso by the abdominal muscles. Due to the abdominal muscles having to generate a lot of force, work hard, to stabilize the torso, many confuse hip flexion exercises with abdominal exercises. This can be potentially harmful as the hip flexors, while working, also cause compression on the spinal discs in the lumbar region. This type of compressive
force combined with improper abdominal movements can lead to lower back pain.

One of the worst exercises for the lower abdominal muscles I have seen in fitness centers are hanging leg raises performed improperly by swinging the legs or allowing the legs to drop completely straight down when lowering legs.

Proper form for this movement is to start in position with your feet positioned forward of your body at approx 30 degrees allowing the pelvis to tip forward, flatten the lower back, and to eliminate the hip flexor as the primary muscle group in action. The motion needs to be slow and controlled through out the entire range of motion and the legs are not to drop below the 30 degree start angle. Beginners should perform a bent knee hanging leg raise. As they improve they can try straight leg.

Hopefully I was able to clear up and/or clarify some questions or concerns you may have.

Feel free to send an email if you have any more questions.

I've found that just plain leg lifts tend to work that same area (if the area you described are what I'm thinking of). They feel really easy at first, but once you start going it feels like your legs suddenly weigh 300 pounds.

I haven't heard of butterfly crunches before. I may start doing those for some variety.