From the Guidelines

Low-dose Aspirin has no significant effect on the rate of Small for Gestational Age (SGA) babies in patients at risk for Preeclampsia.

The study published in the American Journal of Obstetrics and Gynecology in 2020 1 found that the implementation of low-dose aspirin (81mg) between 12 to 16 weeks of gestation did not significantly decrease the rate of SGA babies.
The study was based on the adoption of the ACOG guidelines, which recommended the use of low-dose aspirin for the prevention of superimposed preeclampsia in women with chronic hypertension.
The findings suggest that while low-dose aspirin may have other benefits, it does not have a significant impact on the rate of SGA babies in patients at risk for preeclampsia.

Dose and Timing: The study used a dose of 81mg of aspirin, initiated between 12 to 16 weeks of gestation.
Population: The study focused on women with chronic hypertension, who are at risk for preeclampsia.
Outcome: The study found no significant decrease in the rate of SGA babies, despite the implementation of low-dose aspirin.

From the Research

The use of low-dose aspirin in patients at risk for preeclampsia has been studied in several trials, with varying results regarding its effect on the rate of Small for Gestational Age (SGA) babies 2, 3, 4, 5, 6.
A 2018 meta-analysis found that low-dose aspirin was associated with a significant reduction in the overall risk ratio (RR) of preeclampsia, as well as a reduction in the risk of maternal and neonatal adverse outcomes, including intrauterine growth retardation (IUGR) or small for gestation age infant (SGA) 2.
However, a 2016 meta-analysis of large randomized trials found no impact of low-dose aspirin started before 17 weeks' gestation on the risk of SGA (RR: 0.84; 95% CI: 0.56-1.26) 3.
Another 2016 systematic review and meta-analysis found that low-dose aspirin in multiple gestations was associated with a significant reduction in the risk of preeclampsia, but not SGA neonates (RR, 1.09; 95% CI, 0.80-1.47) 4.
A 2016 review article suggested that low-dose aspirin started in early pregnancy reduces the risk of other placenta-mediated complications such as intrauterine growth restriction (IUGR) and perinatal death 5.
A 2021 recommendation statement from the US Preventive Services Task Force concluded that there is a substantial net benefit of daily low-dose aspirin use to reduce the risk for preeclampsia, preterm birth, small for gestational age/intrauterine growth restriction, and perinatal mortality in pregnant persons at high risk for preeclampsia 6.

Low-dose aspirin may reduce the risk of preeclampsia and associated adverse outcomes, including SGA babies, in patients at risk for preeclampsia 2, 6.
However, the evidence is not consistent, and some studies have found no significant effect of low-dose aspirin on the risk of SGA babies 3, 4.
The timing of low-dose aspirin initiation may be important, with some studies suggesting that initiation before 16-17 weeks' gestation may be more effective in reducing the risk of preeclampsia and associated adverse outcomes 2, 5.