A retrospective population-based cohort study was conducted on 23,736 women giving birth to a singleton baby over a period of 8 years. All women admitted to the obstetric department of a large private hospital in Jeddah, Saudi Arabia, from January 1st, 2010 to December 31st, 2017, were included in the study. Data were collected from a hospital database. The study was approved by the Local Institutional Review Board and Ethics Committee of Bugshan Hospital, Jeddah, Saudi Arabia. All women with a singleton pregnancy who had delivered between 24 and 42 weeks of gestational age were included. In addition, included women were required to have a documented height and pre-pregnancy or first-trimester weight (defined as 13 weeks of gestation or less), and weight at delivery. Pregnant women with pre-gestational diabetes and/or chronic hypertension were excluded from our study. Women with extreme weight gain (greater than 50 kg) or loss (greater than 30 kg) were also excluded, as per Beyerlein et al. 
GWG was derived by means of a pre-pregnancy or first prenatal visit weight at 13 weeks of gestation or less subtracted from a delivery weight. Maternal pre-pregnancy BMI was categorize d into underweight (<18.5 kg/m2), normal (18.5–24.9 kg/m2), and overweight (≥25 kg/m2), according to the classification by the World Health Organization.  GWG was defined as the average weight gained per week during pregnancy, based on the IOM guidelines.  The IOM recommends a GWG of 12.5–18.0 kg for underweight women, 11.5–16.0 kg for normal-weight women, 7.0–11.5 kg for overweight women, and 5.0–9.0 kg for obese women. 
Maternal outcomes evaluated in relation to GWG encompassed the following: hypertensive disorders during pregnancy, gestational diabetes mellitus (GDM), labor induction, failure of labor induction, length of labor, cesarean delivery rate, postpartum hemorrhage (defined as more than 1000 mL of postpartum blood loss), third or fourth degree laceration for women who had a vaginal delivery and postpartum infection (defined as the occurrence of any of the following: endometritis, wound infection or dehiscence after cesarean section or episiotomy). Neonatal outcomes comprised of: preterm birth (defined as a delivery before 37 weeks), shoulder dystocia, macrosomia (defined as a birth weight >90th percentile for gestational age), small for gestational age (SGA; defined as birth-weight < 10th percentile for gestational age) and neonatal hypoglycemia requiring treatment.
Baseline clinical characteristics and maternal and neonatal clinical outcomes were compared according to gestational weight gain categories (below, within, and above the IOM guidelines). The quantitative data with a parametric distribution were presented as mean and standard deviations. Qualitative variables were presented as number and percentages. Comparisons between groups for the qualitative data were done using the Chi-square test, and for quantitative data were done using one-way analysis of variance (ANOVA) testing, as appropriate. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each of the clinical outcomes of interest. Multivariable logistic regression was used to adjust for maternal age, pre-pregnancy BMI, smoking status, parity, prior delivery type, and gestational age at delivery. A p value was considered significant at the level of <0.05. All analyses were performed using the Statistical Package for Social Science (SPSS) version 23 for Windows (IBM Corp., Armonk, NY, USA).
We confirm that all methods were carried out in accordance with relevant guidelines and regulations.
Informed consent was waived by the Local Institutional Review Board of Bugshan Hospital, Jeddah, Saudi Arabia.