Risk factors for small-for-gestational-age and preterm births among 19,269 Tanzanian newborns

Abstract

BackgroundFew studies have differentiated risk factors for term-small for gestational age (SGA), preterm-appropriate for gestational age (AGA), and preterm-SGA, despite evidence of varying risk of child mortality and poor developmental outcomes.MethodsWe analyzed birth outcome data from singleton infants, who were enrolled in a large randomized, double-blind, placebo-controlled trial of neonatal vitamin A supplementation conducted in Tanzania. SGA was defined as birth weight <10th percentile for gestation age and sex using INTERGROWTH standards and preterm birth as delivery at <37 complete weeks of gestation. Risk factors for term-SGA, preterm-AGA, and preterm-SGA were examined independently using log-binomial regression.ResultsAmong 19,269 singleton Tanzanian newborns included in this analysis, 68.3 % were term-AGA, 15.8 % term-SGA, 15.5 % preterm-AGA, and 0.3 % preterm-SGA. In multivariate analyses, significant risk factors for term-SGA included maternal age <20 years, starting antenatal care (ANC) in the 3rd trimester, short maternal stature, being firstborn, and male sex (all p < 0.05). Independent risk factors for preterm-AGA were maternal age <25 years, short maternal stature, firstborns, and decreased wealth (all p < 0.05). In addition, receiving ANC services in the 1st trimester significantly reduced the risk of preterm-AGA (p = 0.01). Significant risk factors for preterm-SGA included maternal age >30 years, being firstborn, and short maternal stature which appeared to carry a particularly strong risk (all p < 0.05).ConclusionOver 30 % of newborns in this large urban and rural cohort of Tanzanian newborns were born preterm and/or SGA. Interventions to promote early attendance to ANC services, reduce unintended young pregnancies, increased maternal height, and reduce poverty may significantly decrease the burden of SGA and preterm birth in sub-Saharan Africa.Trial registrationAustralian New Zealand Clinical Trials Registry (ANZCTR) – ACTRN12610000636055, registered on 3rd August 2010.

Incidence, risk factors and consequences of preterm birth – findings from a multicentric observational study in Nepal

“…The risk of preterm births was higher among both mothers younger than 20 years and above 35 years. Several other studies have also reported linking both younger and older maternal age with preterm births [4,[21][22][23][24][25]. The risk of preterm births was also higher among mothers with education lower than secondary level had a higher risk of having preterm births.…”

Impact of Advanced Maternal Age on Physiologic Adaptations to Pregnancy in Vervet Monkeys

“…Furthermore, infant weight at four days post-delivery was comparable between young and AMA mothers. In humans, one driver of the small gestational phenotype is pre-term delivery 75–78 . This may be a possible explanation for why we did not observe low birth weights in vervets, since AMA did not elicit pre-term delivery in our cohort.…”

Revisiting the Table 2 fallacy: A motivating example examining preeclampsia and preterm birth

“…Given their association with preterm birth, authors may report effect estimates of these confounders alongside the effect estimate for preeclampsia, 13,18 and even more commonly when evaluating preeclampsia as one of multiple risk factors for preterm birth. 17,23,[26][27][28][29] Here, we provide a didactic example of an analysis to estimate the hypothesised effect of preeclampsia on preterm birth among singletons ( Figure 2). In Model 1, we estimate the risk ratio for preeclampsia, adjusting for previous preterm birth, alcohol abuse, and maternal education as secondary factors.…”

“…Because these and other risk factors for preeclampsia are also associated with preterm birth, their potential for confounding the effects of preeclampsia on preterm birth must be considered. Given their association with preterm birth, authors may report effect estimates of these confounders alongside the effect estimate for preeclampsia, and even more commonly when evaluating preeclampsia as one of multiple risk factors for preterm birth …”