Preconceptional and gestational weight trajectories and risk of delivering a small-for-gestational-age baby in rural Gambia.

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. We investigated how preconceptional and gestational weight trajectories (summarized by individual-level traits) are associated with SGA risk in rural Gambia. 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 scores [weight score at 3 mo preconception (wt), weight score at conception, weight score at 3 mo postconception, weight score at 7 mo postconception (wt), 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. Maternal weight at each time point had a consistent nonlinear relation with SGA risk. For example, the wt 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 wt was associated with SGA and only in women with values >-0.5 (RR: 0.579; 95% CI: 0.463, 0.724). 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.