Fetal Weight Easier And More Accurate To Assess With New Generic Reference Tool

A generic tool for assessing fetal weight and birth weight is better at predicting adverse perinatal outcomes than other methods, its developers reported in the medical journal The Lancet. The authors add that it is also much easier to use.

Rafael Mikolajczyk from Bremen Institute for Prevention Research and Social Medicine, Bremen, Germany, Jun Zhang from Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China, and colleagues from other parts of the world developed this global reference method that, according to them, can be easily adapted and used in low-, middle- and high-income countries.

A baby who is small for his/her gestational age is much more likely to die around childbirth, or suffer disability and behavioural disorders, heart disease, hypertension, or diabetes when they are older.

It remains a challenge to create a worldwide definition of infants small for gestational age that is applicable to any country with different maternal populations, the authors explain.

The three currently most common tools used to measure fetal growth are not universally applicable:

• Those based on birth weight are flawed because pre-term babies are probably growth restricted.
• References based on ultrasound – common in women from European ancestry – may be irrelevant to some populations.
• References that take into account maternal and fetal characteristics, known as individualized references are too complex for use in developing nations.

The researchers looked at current ultrasound-based reference tools as their starting point on which to develop. They sketched a new international standard for assessing fetal growth with a reference tool for whole populations or countries that can straightforwardly be adjusted according to the average birth weight at 40 weeks gestation, estimated from the local population.

They compared the performance of the new global reference with ultrasound-based fetal-weight and individualised reference using data from the 2004-2008 WHO Global Survey on Maternal and Perinatal Health, a database of 137,024 births in 24 nations in Asia, Latin America and Africa.

They assessed the risk of stillbirths, neonatal deaths, and Apgar score below 7 at 5 min – or perinatal outcomes – for babies who were small for gestational age to infants who were not.

The new generic reference was found to be better at predicting adverse perinatal outcomes than the fetal-weight reference or the individualized reference. It was also much simpler than the other two. Ethnic origin was the strongest predictor of fetal size.

The authors wrote:

“A definition of small for gestational age should take ethnic origin into account…Adjustment for ethnicity improves the classification of small for gestational age substantially, whereas addition of more parameters for individualisation provides little further improvement against the ethnicity-adjusted reference.

The most important advantage of our method is its simplicity and flexibility, which are important for application in low-resource settings.” “