Abstract
Background: Maternal nutritional status is a key determinant of small for gestational age (SGA), but some knowledge gaps remain, particularly regarding the role of the energy balance entering pregnancy.Objective: We investigated how preconceptional and gestational weight trajectories (summarized by individual-level traits) are associated with SGA risk in rural Gambia.Design: The sample comprised 670 women in a trial with serial weight data (7310 observations) that were available before and during pregnancy. Individual trajectories from 6 mo before conception to 30 wk of gestation were produced with the use of multilevel modeling. Summary traits were expressed as weight z scores [weight z score at 3 mo preconception (zwt−3 mo), weight z score at conception, weight z score at 3 mo postconception, weight z score at 7 mo postconception (zwt+7 mo), and conditional measures that represented the change from the preceding time] and were related to SGA risk with the use of Poisson regression with confounder adjustment; linear splines were used to account for nonlinearity.Results: Maternal weight at each time point had a consistent nonlinear relation with SGA risk. For example, the zwt−3 mo estimate was stronger in women with values ≤0.5 (RR: 0.736; 95% CI: 0.594, 0.910) than in women with values >0.5 (RR: 0.920; 95% CI: 0.682, 1.241). The former group had the highest observed SGA prevalence. Focusing on weight change, only conditional zwt+7 mo was associated with SGA and only in women with values >−0.5 (RR: 0.579; 95% CI: 0.463, 0.724).Conclusions: Protection against delivering an SGA neonate offered by greater preconceptional or gestational weight may be most pronounced in more undernourished and vulnerable women. Independent of this possibility, greater second- and third-trimester weight gain beyond a threshold may be protective. This trial was registered at http://www.isrctn.com/ as ISRCTN49285450.
Highlights
32.4 million babies were born small for gestational age (SGA)6 in 2010, accounting for 27% of births in low- and middle-income countries (LMICs) [1]
To understand the extent to which preconceptional weight was associated with SGA independently of weight during pregnancy, a path model was applied to a subset of participants with zwt23 mo #0.5 in whom we showed a protective association of zwt23 mo with SGA risk
The first key finding was that greater weight at 3 mo preconception was related to lower SGA risk but only in the moreunderweight women who had the highest observed SGA rates
Summary
32.4 million babies were born small for gestational age (SGA) in 2010, accounting for 27% of births in low- and middle-income countries (LMICs) [1]. Part of the relevant literature comprises studies in which maternal weight has been used as an indicator of nutritional status with the aim of providing information about which women are most at risk of delivering an SGA baby and at what time points an intervention might be most effective. Conclusions: Protection against delivering an SGA neonate offered by greater preconceptional or gestational weight may be most pronounced in more undernourished and vulnerable women. Independent of this possibility, greater second- and third-trimester weight gain beyond a threshold may be protective.
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