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International study provides first universal standard for pregnancy dating

ISUOG News: 2 December 2014

Research published in the journal Ultrasound in Obstetrics & Gynecology has produced, for the first time, international growth charts to predict the health of a fetus and a woman’s due date in the first phase of pregnancy.

The study, led by a team at the University of Oxford, collected data from 4607 women in eight geographically diverse urban areas across the world to establish growth charts that can be applied in any clinic, in any city, in any country.

Dr Aris Papageorghiou from the University of Oxford who led the study, commented, ‘A lot of assumptions are still made about the size a fetus should be, particularly in the first trimester, which we would argue are irrelevant as they are made in reference to descriptive data collected about how a fetus does grow in certain countries and regions.’

Fetal size is an important indicator of health and of the expected birth date. It is commonly used in the first trimester of pregnancy to give an accurate measure of gestational age (weeks and days since fertilisation) and is calculated using the greatest linear size of the fetus, measured from the top of its head to its rump (known as the crown-rump length). 

This study, which is part of the global INTERGROWTH-21st project, aimed to evaluate fetal growth patterns to account for ethnic and geographical diversity and to provide a robust method for interpreting fetal size that omits localised variables.

By conducting an evaluation of fetal size in the first trimester across women from a range of ethnic and geographical backgrounds and controlling for health, disease, education, and even clinical care and data collection, the team revealed that ethnicity and location account for a very minimal difference in fetal size.

Dr Papageorghiou explains, ‘In other words, the potential for fetal growth is the same wherever you are in the world. Therefore, standardising fetal growth charts will help us to better prescribe the health of a fetus and pregnancy dating in the first trimester, rather than basing our health guidance on local assumptions which can be transient, e.g disease, nutrition and wealth of populations.’

Professor Basky Thilaganthan, Editor in Chief of the journal Ultrasound in Obstetrics and Gynecology adds, ‘The study highlights the importance of international standardisation of the methodology used to create growth charts in order to give an accurate reflection of health and wellbeing, in this context for fetal growth and pregnancy dating.’

The new standardised tables, published in Ultrasound in Obstetric & Gynecology's December issue will make comparisons of fetal size and pregnancy dating universally easier to interpret.

To find out more about this study ISUOG members can hear from the research lead, Dr Aris Papageorghiou, who presented the preliminary results at ISUOG’s 24th World Congress in Barcelona, September 2014. Watch this presentation, online, here.


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