Sexual and reproductive health

WHO publishes new multinational fetal growth charts

New research shows variation in fetal growth between countries.

24 January 2017: A new study, published today by PLOS Medicine, shows that there is significant variation in fetal growth between countries. The study also found that fetal growth was to some extent influenced by maternal age, height, weight, parity and by fetal sex. A significant variation in birth weight was also observed between countries. The article which is open access also provides new WHO charts for estimating fetal growth and should be particularly useful for countries who may not have resources to develop their own charts.

A doctor performs ultrasound at a Hospital, Tigray region, Ethiopia
UNICEF/Ose

The research, that included 1387 healthy women with low-risk pregnancies, was a collaboration between WHO’s Department of Reproductive Health and Research and the Special Programme of Research (HRP) together with investigators from 10 countries (Argentina, Brazil, Democratic Republic of Congo, Denmark, Egypt, France, Germany, India, Norway and Thailand).

Using repeated ultrasound measurements the researchers were able to establish fetal growth charts for head and abdominal circumference, length of thigh bone and fetal weight. Estimating fetal weight is important as small size at birth is associated with perinatal mortality and child morbidity as well as longer-term health risks as an adult.

Ultrasound estimation of fetal weight is widely used and is a key tool in identifying and managing high-risk pregnancies. Many countries, however, use fetal growth charts that are based on a single population from high-income countries. The differences observed between countries in the WHO study, with regard to maternal factors (for example age, weight, parity) and fetal sex, indicate that local diagnosis may be improved when these factors are taken into account. Using the new WHO internationally-adjusted fetal growth charts is therefore recommended. The study includes an example of fetal growth charts that have been adjusted for sex. Building on the results of this study, WHO is currently developing guidance that will allow countries to develop fetal growth charts specific to their own country.