Patterns of Fetal Growth Based on Ultrasound Measurement and its Relationship with Small for Gestational Age at Birth in Rural Vietnam Phuong Hong Nguyen, a,b O. Yaw Addo, c Melissa Young, c Ines Gonzalez-Casanova, c Hoa Pham, a Truong V. Truong, a Son Nguyen, a Reynaldo Martorell, c Usha Ramakrishnan c a Thai Nguyen University of Pharmacy and Medicine, Thai Nguyen, Vietnam b International Food Policy Research Institute, Hanoi, Vietnam c Hubert Department of Global Health, Emory University, Atlanta, GA Abstract Background: Small for gestational age (SGA) is a global health problem. Identifying the timing of fetal growth faltering is critical for developing preventive interventions. We aim to describe patterns of fetal growth and to predict SGA at birth using fetal ultrasound measurements. Methods: We studied 1412 pregnant women enrolled in a randomised-controlled trial evaluating maternal micronutrient supplementation in Thai Nguyen province, Vietnam. Ultrasound examinations included biparietal diameter (BPD), head circumference (HC) and abdominal circumference (AC), and femur length (FL). Measures were assessed using the new international fetal growth standards (INTERGROWTH-21st Project). Generalised linear mixed logit regression models were used to examine the association between ultrasound measures and SGA at birth. Results: Overall fetal growth restriction began in early pregnancy and continued through delivery, but the timing of growth faltering varied by measure: it began by 20 weeks for HC, BPD and AC, earlier as compared to FL growth that started >30 weeks. SGA infants had significantly lower mean fetal growth parameters as early as 14 weeks. Ultrasound measures below the 10th percentile were associated with a two to four times higher risk of SGA at birth compared to fetuses greater than the 50th percentile, with the largest odds ratios for AC (OR 3.9, 95% confidence interval (CI) 2.7, 5.7). Conclusions: Fetal growth faltering by ultrasound begins in early gestation among rural Vietnamese populations; these patterns clearly identified those to be born SGA. Efforts to prevent fetal growth faltering must begin early in pregnancy and perhaps even before pregnancy. Keywords: fetal growth, ultrasound, small for gestational age, Vietnam. Small for gestational age (SGA), defined as a weight- for-age below the 10th percentile of a reference, remains a global public health concern. In 2010, it was estimated that 27% (32.4 million) infants were born SGA in low- and middle-income countries (LMIC), with a third of SGA infants being born in Asia. 1 SGA is a proxy of fetal growth restriction and has impor- tant short- and long-term consequences such as increased morbidity, mortality, and impaired growth and cognitive development. 2,3 Early detection of SGA using ultrasound measure- ments has been suggested as a critical first step to identify and implement appropriate interventions. Ultrasound examinations are recommended as part of routine prenatal care to assess gestational age, fetal growth, pregnancy abnormalities, and is a useful tool for predicting SGA. 4–6 However, in LMICs, research on the detection and development of effective strate- gies to mitigate the risks associated with fetal growth failure is lacking. A study in rural Guatemala found that children born SGA showed signs of growth falter- ing as early as the 15th week of gestation. 7 Similar studies are needed for the early detection of children at risk of SGA in other low resource settings. 8,9 Furthermore, until recently there was no consensus on standards to compare measures of fetal growth. 10 Correspondence: Phuong Hong Nguyen, IFPRI, Vietnam, c/o Alive & Thrive, Vietnam, Room 203-204, E4B, Trung Tu Diplomatic Compound, No 6, Dang Van Ngu, Hanoi, Vietnam. E-mail: p.h.nguyen@cgiar.org © 2016 John Wiley & Sons Ltd Paediatric and Perinatal Epidemiology, 2016, 30, 256–266 256 doi: 10.1111/ppe.12276