The 2009 Institute of Medicine (IOM) gestational weight gain (GWG) guidelines were initially developed for pregnant women in the United States.
This study aimed to investigate whether the IOM guidelines were suitable for pregnant Chinese women.
A retrospective cohort study comprising 20,593 singleton pregnant women was conducted at the Beijing Obstetrics and Gynaecology Hospital (1 January 2018 to 31 December 2019). Applicability was evaluated by comparing the GWG corresponding to the lowest point of the predicted composite risk curve with the 2009 IOM GWG Guidelines. The IOM Guidelines serve as the standard for the GWG categories and the pre-pregnancy body mass index. An exponential function model was used to fit the weight gain during pregnancy and the probability of caesarean section, preterm birth, small for gestational age, and large for gestational age. A quadratic function model was used to fit the combined probability of the above-mentioned adverse pregnancy outcomes. The applicability of the IOM guidelines was evaluated by comparing the weights corresponding to the lowest predicted probability with the GWG range recommended by the IOM guidelines.
According to the 2009 IOM GWG Guidelines, 43% of the women achieved adequate weight, almost 32% gained excessive weight, and 25% gained inadequate weight. The GWG range proposed by the IOM included the lowest predicted probability value for underweight women and exceeded the lowest predicted probability for normal weight, overweight, and obese women.
The 2009 IOM guidelines were suitable for Chinese women whose pre-pregnancy body mass index was classified as underweight. The guidelines were not suitable for normal, overweight, or obese pre-pregnancy body mass index classifications. Therefore, based on the above evidence, the 2009 IOM guidelines are not suitable for all Chinese women.

OBJECTIVE: To analyze the associations between gestational weight gain (GWG) and perinatal outcomes based on the GWG guidelines of the Chinese Nutrition Society (CNS) and the Institute of Medicine (IOM).
METHODS: This was a retrospective study with 9075 low-risk singleton pregnant women. Logistic regression model was used to analyze associations between GWG categories and perinatal outcomes. Sensitivity analyses were performed based on pre-pregnancy body mass index (calculated as weight in kilograms divided by the square of height in meters).
RESULTS: Excessive GWG as defined by the two guidelines was associated with a higher risk of adverse perinatal outcomes. Inadequate GWG was associated with higher risks of small for gestational age (adjusted odds ratio [aOR] 1.34, 95% confidence interval [CI] 1.10-1.64) and preterm birth (aOR 1.70, 95% CI 1.22-2.36), but a lower risk of large for gestational age (LGA) (aOR 0.77, 95% CI 0.63-0.95) according to the IOM guidelines. When using the CNS guidelines, inadequate GWG was associated with only a lower risk of preterm birth (aOR 1.80, 95% CI 1.19-2.70). Sensitivity analyses suggested that excessive GWG was associated with a higher risk of LGA in underweight women.
CONCLUSIONS: Both guidelines could demonstrate the relationship between GWG and adverse perinatal outcomes. The CNS guidelines were more suitable for the Chinese population with underweight or normal weight before pregnancy, whereas IOM was more suitable for pregnant women with inadequate GWG.

The applicability of the Institute of Medicine (IOM) recommendations of gestational weight gain (GWG) for Chinese twin gestations is uncertain. In this article, we aimed to investigate the associations between GWG among twin gestations, as categorized according to the 2009 IOM guidelines and perinatal outcomes in Chengdu, China. A retrospective cohort study of pregnant women delivering live twins ≥28 weeks at a tertiary maternal and child hospital was conducted. The incidences of perinatal outcomes were compared across 3 groups-that is, women with low, adequate, and excessive GWG. Logistic regression analyses were next performed to confirm the associations while taking into account potential confounders. Results showed that low GWG was associated with a higher risk of preterm birth, low and very low birthweight, neonatal intensive care unit admission, and gestational diabetes, whereas preeclampsia was more frequent among excessive GWG women. In conclusion, adherence to the 2009 IOM guidelines for twin pregnancies are associated with improved perinatal outcomes. This has the potential to improve short- and long-term public health outcomes.