Abstract
Fetal growth restriction is a strong risk factor for perinatal morbidity and mortality. Reliable standards are indispensable, both to assess fetal growth and to evaluate birthweight and early postnatal growth in infants born preterm. The aim of this study was to create updated Swedish reference ranges for estimated fetal weight (EFW) from gestational week 12–42. This prospective longitudinal multicentre study included 583 women without known conditions causing aberrant fetal growth. Each woman was assigned a randomly selected protocol of five ultrasound scans from gestational week 12 + 3 to 41 + 6. Hadlock’s 3rd formula was used to estimate fetal weight. A two-level hierarchical regression model was employed to calculate the expected median and variance, expressed in standard deviations and percentiles, for EFW. EFW was higher for males than females. The reference ranges were compared with the presently used Swedish, and international reference ranges. Our reference ranges had higher EFW than the presently used Swedish reference ranges from gestational week 33, and higher median, 2.5th and 97.5th percentiles from gestational week 24 compared with INTERGROWTH-21st. The new reference ranges can be used both for assessment of intrauterine fetal weight and growth, and early postnatal growth in children born preterm.
Highlights
The World Health Organization Multicentre Growth Reference Study and the INTERGROWTH-21st have presented fetal growth standards intended for universal use in all populations[20,21]
In 145 women (25%), a scan was performed and registered outside the randomization protocol. These scans corresponded to the routine second trimester scan in 139 women, and the remaining 6 scans were performed in gestational week 22, 26, 30, 32, and 35, respectively
In this study we present new Swedish reference ranges of estimated fetal weight (EFW) by GA to be used for assessing fetal weight and growth from gestational week 12 to 42
Summary
The World Health Organization Multicentre Growth Reference Study and the INTERGROWTH-21st have presented fetal growth standards intended for universal use in all populations[20,21]. The currently used Swedish growth reference ranges for estimated fetal weight (EFW) were published in 1996 by Maršál et al, and present EFW from gestational week 25 to 43. To meet up with these obstetrical challenges, there is a need for updated national reference ranges, which reflect expected fetal growth throughout the second trimester in a representative and healthy population. The aim of this study was to create new national reference ranges for EFW from gestational week 12 to 42, applying modern statistical methods to a longitudinal study of ultrasonically derived intrauterine biometric measurements in a large Swedish cohort of healthy pregnant women with expected normal fetal growth. We wanted to compare the new reference ranges with other relevant growth reference ranges of EFW
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