Background Gestational diabetes mellitus (GDM) is a common cause of maternal morbidity, and can lead to the development of diabetes later in life. Pre-pregnancy body weight is associated with the change in body mass index (BMI) between a first and second pregnancy. Compared with long-term change in BMI between pregnancies, the most accessible follow-up point to investigate BMI change is 6 weeks after the initial pregnancy. The present study aimed to assess the association between weight retention at 6 weeks postpartum and the risk of GDM in a subsequent pregnancy. Methods We recruited 6429 singleton pregnancies into this retrospective cohort study. For each pregnancy, we calculated weight retention at 6 weeks postpartum after the first pregnancy, the interpregnancy BMI change between pregnancies, and the gestational weight gain in the second pregnancy. Risk was represented by the odds ratio (OR) and 95% confidence intervals (CIs). We then determined the relationship between postpartum weight retention at 6 weeks after the initial pregnancy, and the interpregnancy change in BMI between pregnancies. Analyses were stratified by BMI during the first pregnancy. Results Compared to women with a stable BMI (− 1 to 1), interpregnancy BMI gains were associated with an increased risk of GDM in the second pregnancy. Risk increased significantly for women with a BMI below and above 25 during the first pregnancy, although the increase was greater in the women with a BMI < 25. The risk of GDM in the second pregnancy was higher in women with inadequate weight gain during the second gestation. The weight retention at 6 weeks postpartum, where there was a gain of > 3 BMI units was significantly more related to weight gain more than when there was 1 BMI unit gain between pregnancies ( P < 0.05) and associated with an increased incidence of GDM in the second pregnancy (OR = 2.95, 95% CI: 1.95 ~ 4.45). Women who showed a change in BMI that was > 3 units at 6 weeks postpartum after the first pregnancy showed an increased risk for BMI subsequently (OR = 1.42, 95% CI: 1.08~1.87). Conclusions Women who gained more than 3 BMI units at 6 weeks postpartum were associated with an increased risk of BMI in a subsequent pregnancy. Six weeks postpartum provides a new early window of opportunity to identify risk factors for a subsequent pregnancy and allows us to implement primary prevention strategies.

Dictyostelium robusticaule and Heterostelium recretum are two new species of dictyostelids reported in this study. The potential use of atp1 sequences is a complement of SSU rDNA sequences for the identifying dictyostelids.

Dictyostelium quercibrachium and D. crassicaule were isolated from samples of soil collected on Changbai Mountain, Jilin Province, China. Dictyostelium quercibrachium represents a new record from China; and D. crassicaule, represents a new record from Jilin Province. Descriptions and illustrations based on these isolates are provided.