Study of birthweight of liveborn babies at Maharaj Nakorn Chiang Mai Hospital.

386 pregnant women attending ANC unit, Maharaj Nakorn Chiang Mai Hospital, during May 1983 to Febuary 19&), were recruited to study their liveborn babies' birthweight. The criteria for inclusion of these women were ;having had gestational age at or less than 16 weeks; able to remember their LMPs ; having history of regular menstruation; not using hormonal contraceptives at least 3 months before becoming pregnant and good correlation of gestational age as calculated from LMP and as estimated from uterine size. Only 329 eases were followed through until delivery by the same group of obstetricians. Estimation of gestational age of the newborns using Dubowilz's seore were done by the pediatrician who is one of the investigators. It was found that mean birt hweight (± S.O) of newborns with gestational age of less than 38 weeks was 2,586.7 (± 569.4) grams; 38-42 weeks was 3,099.3 (± 380.5) grams; and more than 42 weeks was 3,064.3 (± 255.7) grams. The 10th, 50th and 90th percentile of birthweight at 3~ 42 weeks of gestational age were 2,G03, 3,094 and 3,610 grams,res[lectivcly. Thc incidence of low birthweight ( < 2,500 grams) among newborns with 38-42 wccks of gestation was 4.40 % (12/273). Newborns with 38 -42 weeks,who weighed 4,000 grams or more, was 1.1 % (3/273).