On weight gain during pregnancy: relationships between weight gain during pregnancy, duration of pregnancy and the somatic classification of neonates.

Background: Weight gain during pregnancy is an important parameter that is related to a number of perinatal outcomes. We aimed to analyse the relationships between weight gain during pregnancy, duration of pregnancy, and the somatic classification of the neonates as small, appropriate, or large for gestational age (SGA, AGA, LGA).

Material And Methods: Data were from the German perinatal survey of 1995-2000 (more than 2.2 million singleton pregnancies). We classified all neonates with a birth weight below the 10th population percentile as SGA, those with a birth weight above the 90th percentile as LGA, and all others were AGA. Duration of pregnancy (categorised as ≤ 36, 37-41, or ≥ 42 completed weeks of gestation) and the percentages of SGA, AGA, and LGA neonates were analysed according to maternal weight gain in 1-kg-steps.

Results: Small weight gain was associated with higher rates of preterm birth, i.e. birth after ≤ 36 completed weeks of gestation (preterm birth rates >10% for women who gained <9 kg). SGA rates were greater for low weight gain values and LGA rates were greater for high weight gain values. For weight gains <12 kg, SGA rates were always >10%. For weight gains >14 kg LGA rates were always >10% reaching LGA rates >25% for weight gains in the range 33-35 kg.

Conclusions: Weight gain during pregnancy may be of use as a predictor of perinatal outcomes such as the somatic classification of neonates. Further analyses taking account of factors influencing the weight gain during pregnancy are warranted.