Small-for-gestational age (SGA) infants are at significantly increased risk of perinatal complications, but the risk of recurrent SGA is not well known, particularly as there are many demographic and obstetric factors that interact and modify this risk. We investigated the relationship between previous SGA births and the risk of recurrence at term in a large Australian cohort.
We aimed to identify key demographic and obstetric variables that influence the risk of recurrence of an SGA infant at term. The primary outcome measure was the odds of recurrence of SGA in subsequent pregnancies up to a maximum of four consecutive term births.
This was a retrospective analysis of women who had more than one consecutive non anomalous, singleton, term live births between July 1997 and September 2018 at the Mater Mother’s Hospital in Brisbane Australia. Women with multiple pregnancy, preterm birth or major congenital malformations were excluded. SGA was defined as birthweight <10 centile. We calculated the odds of recurrence depending on the number of previous SGA infants as well as if only the preceding infant was SGA. The study population was dichotomized into SGA and non-SGA for each consecutive pregnancy. Univariate analyses compared baseline demographic and obstetric characteristics followed by logistic regression modelling to determine the odds of recurrence in the second, third, and fourth pregnancies.
The final study comprised 24,819 women. The proportion of women that had a SGA infant in their first pregnancy was 9.4%, whilst the proportion of women that had an SGA infant in their second, third, and fourth pregnancies following the birth of a previous SGA infant were 20.5% (479/2338), 24.6% (63/256) and 30.4% (14/46) respectively. Regardless of parity, the odds of recurrence increased if the preceding infant was SGA. The odds of recurrence increased markedly if there was more than one previous SGA infant. In women with three previous SGA infants, the adjusted odds of another SGA infant were 66.00 (95% CI 11.35-383.76). Maternal age, body mass index, ethnicity and smoking were significant risk factors for recurrent SGA. However, maternal diabetes mellitus or hypertension, either in a previous or current pregnancy, did not influence the risk of recurrence.
The risk of recurrence in a subsequent pregnancy increased if there was a previous SGA birth. Women with consecutive SGA infants were at highest risk of recurrence. Our results highlight that women with a previous SGA infant are at substantial risk of another small infant and need to be counselled and monitored appropriately.

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