Determining gestational age of the newborn

There are a few methods for determining the gestational age of the infant. Let’s explore the options.

The gestational age is often manually calculated from the first day of the mother’s last menstrual period. This date is used because the exact date of conception is often unknown. That being said, menstrual history may not always be accurate either.

Nowadays, most women have access to fetal ultrasound which pinpoints gestational age of the fetus to the nearest day. However, a third way of determining gestational age is through the use of the New Ballard Scoring System. This set of procedures, developed by Dr Jeanne Ballard, determines gestational age through neuromuscular and physical assessments of the newborn. The scoring system is most accurate when performed in the first 12-20 hours of life (Arshpreet, 2017).

The system uses both neuromuscular and physical maturity indicators to determine the gestational age. However, in terms of neuromuscular maturation, six indicators are considered:

1. Posture

As the fetus approaches term, the posture becomes more flexed. By placing the newborn on its back in a relaxed posture, the flexion of the hips should result in a frog-like posture, where the knees will naturally draw up. The more term the baby, the more flexed the hips will be.

2. Square window

To test the square window, the healthcare professional performing the assessment straightens the baby’s fingers and applies gentle pressure to the back of the hand (close to the fingers). Preterm babies will have greater angles of flexion at the wrist. The younger the gestational age, the less flexibility at the wrist.

3. Arm recoil

This test assesses the passive flexor tone of the newborn’s biceps muscle, by measuring the angle of recoil following a brief extension of the upper arm. To test arm recoil:

• position the baby comfortably on their back and place one hand beneath the elbow for support

• next, take the baby’s hand and briefly set the elbow in flexion, before momentarily extending the arm before releasing the hand.

The angle of recoil to which the forearm springs back into flexion is noted, and the appropriate square is selected on the score sheet. The extremely preterm neonate will not exhibit any arm recoil.

4. Popliteal angle

Gently press the baby’s thigh against their abdomen and measure the popliteal angle by moving the foot gently towards the head, until the first sign of resistance. If you haven’t come across the word before, popliteal refers to the area behind the knee. You will find that babies born at term are less flexible, with about a 90° popliteal angle. With very preterm neonates, the leg straightens to a 180° angle.

5. Scarf sign

The scarf sign can be assessed by grasping the baby’s hand and attempting to cross their arm over the body towards their neck. The arms of term babies will meet resistance before crossing the mid-line, while preterm babies cross the elbow past the mid-line with no resistance.

Your task

Access the online version of The New Ballard Score or download and print a PDF copy for your reference. Take a few minutes to review the scoring criteria and then move to the quiz in the next step to put theory into practice.

References

Arshpreet, D. (2017). Validity of Modified Ballard Score after 7 Days of Life. International Journal of Medical Research and Health Sciences, 6(7), 79-83.