Indian J Pediatr 1987; 54 : 926-929 Etiological factors and perinatal risks in symmetrical and asymmetrical intrauterine growth retardation M. Sood, S. Kumar, N. Kashyap*, M. Berry*, S. Bhargava* and V. Hingorani Departments of Obstetrics and Gynecology and *Radiology, All India Institute of Medical Sciences, New Delhi Fetuses with intrauterine growth retardation (IUGR) are of two types--symmetrieal and asymmetrical, and it is important to differentiate between the two types ante- natally. Ultrasound studies on 22 patients with IUGR were done after 28 weeks o f gestation. The fetuses were distinguished as symmetrical and asymmetrical on the basis of ratio of head to abdominal circumference. It was found that the ratio of head to abdominal circumference differentiated well between the two types of IUGR after 36 weeks of gestation. The etiology and perinatal behaviour in the two groups were also different. ,4 single head : abdominal circumference ratio may be useful in differentiating between symmetrical and asymmetrical IUGR after 36 weeks. Key words : Intrauterine growth retardation; IUGR. Babies with intrauterine growth retar- dation (1UGR) are not a homogeneous population, and at least two morpho- logical groups are distinguished: One is the symmetrical IUGR in which there is a reduction in the size of all the organs, and the second is the asymmetrical IUGR in which the baby has a long and wasted body with a relatively large head which has been preferentially spared from the full effects of the growth retardation. Western studies have suggested that the etiological mechanism and the perinatal and long-term risks differ in the two Reprint requests : Dr. Mini Sood, Department of Obstetrics and Gynecology, All India Institute of MedicalSciences, AnsariNagar, NewDelhi 110029, 926 groups. 2 Antenatally the two types of growth retardation can be differentiated by following the fetal biparietal diameter (BPD) and the ratio of the head circum- ference to the abdominal circumference (HC/AC).3 However, these conclusions do not necessarily apply in India, since the normal ultrasound measurements of head circumference and abdominal cir- cumference in Indian fetuses are lower than those reported in the west. 4 This is a report of our experience with 22 IUGR babies studied from the 28th week of gestation onwards and describes our normal and abnormal measurements, and the etiological factors in the two types of growth retardation.