Maternal height, and ethnicity and birth weight: A retrospective cohort study of uncomplicated term vaginal deliveries in Malaysia.

Background: Small for gestational age (SGA) and large for gestational age (LGA) are designations given to neonates based solely on birthweight, with no distinction made for maternal height. However, there is a possibility that maternal height is significantly correlated with neonatal birthweight, and if so, SGA and LGA cutoffs specific to maternal height may be a more precise and useful tool for clinicians. To explore this possibility, we analyzed the association between maternal height and ethnicity and neonate birthweight in women with low-risk, 37- to 40-week gestation, singleton pregnancies who gave birth vaginally between 2010 and 2017 (n = 354,488). For this retrospective cohort study, we used electronic obstetric records obtained from the National Obstetrics Registry in Malaysia.

Methods: National Obstetric Registry (NOR) data were used to calculate the 10th and 90th birthweight percentiles for each maternal height group by gestational age and neonatal sex. Multiple linear regression models, adjusted for maternal age, weight, parity, gestational age, and neonatal sex, were used to examine the association between neonate birthweight and maternal ethnicity and height. The following main outcome measures were assessed: small for gestational age (<10th percentile), large for gestational age (>90th percentile), and birthweight.

Results: The median height was 155 cm (IQR, 152-159), with mothers of Chinese descent being the tallest (median (IQR): 158 cm (154-162)) and mothers of Orang Asli (Indigenous) descent the shortest (median (IQR): 151 cm (147-155)). The median birthweight was 3000 g (IQR, 2740-3250), with mothers of Malay and Chinese ethnicity and Others having, on average, the heaviest babies, followed by other Bumiputeras (indigenous) mothers, mothers of Indian ethnicity, and lastly, mothers of Orang Asli ethnicity. For infants, maternal age, height, weight, parity, male sex, and gestational age were positively associated with birthweight. Maternal height had a positive association with neonate birthweight (B = 7.08, 95% CI: 6.85-7.31). For ethnicity, compared with neonates of Malay ethnicity, neonates of Chinese, Indian, Orang Asli, and other Bumiputera ethnicities had lower birthweights.

Conclusion: Birthweight increases with maternal height among Malaysians of all ethnicities. SGA and LGA cutoffs specific to maternal height may be useful to guide pregnancy management.