Why do aboriginal newborns weigh less? Gestational age at delivery: estimation, distribution and determinants.

We reviewed birth records pertaining to 1,301 Western Australian singleton Aboriginal pregnancies dated before 24 weeks by ultrasound fetometry using Caucasian standards. We compared i) ultrasound- and LMP-derived estimates of age at delivery for 323 pregnancies with available last menstrual period (LMP) dates and ii) distributions of ultrasound-estimated age at delivery for full-blood with part-blood Aboriginal neonates and with statutorily collected estimates for Caucasian neonates. We investigated determinants of age at delivery for Aboriginal neonates. Ultrasound-derived estimates of gestational age for Aboriginal pregnancies were statistically but not clinically significantly shorter than estimates derived from LMP dates claimed to be certain: mean difference = 0.4 weeks (95% CI:0.09-0.71). Aboriginal gestations were shorter than Caucasians' by 2 weeks (median) or 1 week (mode). Some shortening of gestation was accounted for by antepartum haemorrhage, congenital anomaly, history of syphilis, diabetes, hypertensive disease and inductions before 40 weeks without recorded medical complication but not by full-blood (relative to part-blood) Aboriginality. We conclude that Caucasian fetometry standards gave gestational estimates acceptably close to those derived from certain menstrual dates for dating scan before 24 weeks. Aboriginal gestations tended to be shorter than Caucasian gestations but since factors recorded in the medical record accounted for little of this difference, socioeconomic factors may be partly responsible.

Hospital admissions before the age of 2 years in Western Australia.

A linked data file of birth records and hospital admissions was used to investigate inpatient hospital morbidity before 2 years of age for all non-Aboriginal and Aboriginal children born in Western Australia in 1986. Of the non-Aboriginal children, 31.8% were admitted to hospital at least once before the age of 2 years, with an overall admission rate of 526/1000 live births; the corresponding figures for Aboriginal children were 68.7% and 2797. The mean number of days in hospital for each non-Aboriginal child admitted was 7.4, and 26.5 for Aboriginal children. Of the total cohort, 21% of non-Aboriginal and 20% of Aboriginal children were admitted only once, and 4% of non-Aboriginal and 36% of Aboriginal children were admitted at least three times; 23% of non-Aboriginal and 24% of Aboriginal children were admitted for only one major disease category, and 1% of non-Aboriginal and 16% of Aboriginal children were in at least four categories. The highest admission rates and highest percentages of the cohort admitted were for gastrointestinal and respiratory diseases and social admissions. These results illustrate the importance for both descriptive and analytical research of relating admissions to hospital for the total population to the individual child, and of using clinically relevant disease classifications.

Genitourinary tract infections in pregnancy and low birth weight: case-control study in Australian aboriginal women.

OBJECTIVE: To investigate the association between genital and urinary tract infections in pregnant Aboriginal women and low birth weight. DESIGN: Retrospective case-control study controlling for potential confounding variables. SETTING: Western Australia from 1985 to 1987. SUBJECTS: All Aboriginal women (n = 269) who had given birth to singleton infants weighing 2250 g or less (cases), and 269 randomly selected Aboriginal women who had given birth to singleton infants weighing 3000 g or more (controls). MAIN OUTCOME MEASURES: Proportions of women in case and control groups who had had genital and urinary tract infections; odds ratios for low birth weight when genitourinary tract infection was present; population attributable fraction of low birth weight to genitourinary tract infection. RESULTS: At the time of delivery 51% of women in the case group (109/215) had genitourinary tract infections compared with 13% of controls (35/266). After controlling for potential confounding variables the odds ratio for giving birth to infants weighing 2250 g or less when genitourinary tract infection was present was 4.0 (95% confidence interval 2.3 to 7.0). The proportion of infants with low birth weight attributable to genitourinary tract infection in the whole population of Aboriginal women was 32% (95% confidence interval 17% to 49%). CONCLUSIONS: There was a strong association between low birth weight and the presence of genitourinary tract infections in Aboriginal women both during pregnancy and at the time of delivery. A community intervention trial of screening and treatment of genitourinary infections in this population is recommended.