Impact of gestational weight gain on maternal and neonatal clinical outcomes: A retrospective cohort study.

We aim to explore the association between gestational weight gain and adverse events during pregnancy. A retrospective study was conducted to evaluate the perinatal outcomes in singleton women whose weight gain during pregnancy was below, within, or above the 2009 Institute of Medicine's (IOM) guidelines, and delivered between 24 and 42 weeks’ gestation. GWG was derived using weight at delivery minus the pre-pregnancy or rst trimester weight. Our results indicated that mothers with low GWG had increased odds of having small-for-gestational-age neonates (adjusted OR 1.202; 95% CI 1.031-1.403), and preterm birth (adjusted OR 2.03; 95% CI 1.769-2.439), but decreased odds of having macrosomia (adjusted OR 0.523; 95% CI 0.24-0.991). Meanwhile, mothers with GWG above the IOM recommendations had higher odds of having hypertensive disease of pregnancy (adjusted OR 2.07; 95% CI 1.314-3.535), gestational diabetes (adjusted OR 1.227; 95% CI 1.038-1.448), cesarean section (adjusted OR 1.34; 95% CI 1.279-1.512), induced labor (adjusted OR 1. 219; 95% CI 1.051-1.409), failure of induced labor (adjusted OR 1.432; 95% CI 1.03-1.992), macrosomia (adjusted OR 1.987; 95% CI 1.384-2.725), and shoulder dystocia (adjusted OR 1.715; 95% CI 1.292-2.18. In conclusion, GWG is an important predictor of adverse maternal and neonatal outcomes during pregnancy. 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% condence intervals (CIs) were calculated for each of the clinical outcomes of interest. Multivariable logistic regression was at p analyses Statistical Social and neonatal clinical outcomes whether by excessive or reduced maternal GWG. The of the is associated with deleterious maternal and neonatal consequences including hypertensive disease of pregnancy, gestational diabetes, rates of induced labor, failure of induced labor, cesarean delivery, neonates that are small for gestational age, preterm birth, macrosomia, and shoulder dystocia.


Introduction
Gestational weight gain (GWG) is a distinctive and composite biological phenomenon that supports the functions of fetal growth and development. [1] However, the great variability and differences in GWG observed in pregnant females maybe affected by ethnic and racial variation, the medical status of the patient, including the presence of pre-existing conditions such as diabetes mellitus and hypertension. [2] Research conducted across the world has considered the impact of GWG on maternal and fetal clinical outcomes. [3][4][5] Excess or de cient GWG is associated with a higher risk of adverse pregnancy outcomes, including preterm birth, macrosomia, and cesarean delivery. [5] Clinically, it is considered unfavorable to have excessive weight gain in women suffering from obesity. On the other hand, underweight women are considered high-risk cases if they do not gain the weight required for the normal, physiologically complex, and interactive processes occurring during pregnancy. [6] The weight gain process can be in uenced by lifestyle and dietary patterns before and throughout pregnancy. [7,8] In attempts to improve health outcomes, the Institute of Medicine's (IOM) 2009 guidelines categorize the appropriateness of GWG with reference to pre-pregnancy body mass index (BMI). [9] Despite various research studies investigating the impact of gestational weight gain on perinatal outcomes, no studies have evaluated the relationship between GWG and perinatal outcomes in the Middle East or Saudi Arabia. Therefore, the objective of this study was to evaluate the maternal and neonatal clinical outcomes with regard to GWG at a large private hospital in Jeddah, Saudi Arabia.

Materials And Methods
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. 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 rst-trimester weight (de ned 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. [10] GWG was derived by means of a pre-pregnancy or rst 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 classi cation by the World Health Organization. [11] GWG was de ned as the average weight gained per week during pregnancy, based on the IOM guidelines. [9] 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. [9] 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 (de ned as more than 1000 mL of postpartum blood loss), third or fourth degree laceration for women who had a vaginal delivery and postpartum infection (de ned as the occurrence of any of the following: endometritis, wound infection or dehiscence after cesarean section or episiotomy). Neonatal outcomes comprised of: preterm birth (de ned as a delivery before 37 weeks), shoulder dystocia, macrosomia (de ned as a birth weight >90th percentile for gestational age), small for gestational age (SGA; de ned 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% con dence 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 signi cant 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).

Results
Initial recruitment included 23,736 women. 14,364 women were eligible for our study. Based on the IOM guidelines, 3,045 (21.2%) women had low GWG, 3,993 (27.8%) women had normal GWG, and 7,326 (51%) women had high GWG (Figure 1). Table 1 reveals the demographic characteristics of the research study cohort comparing low, normal, and high GWG research groups. There was a statistically signi cant difference between them in relation to age, nulliparity, pre-pregnancy BMI, smoking, and gestational age at delivery (ps <0.001). There was also a statistically signi cant difference observed with regards to prior cesarean delivery (p = 0.013).  Table 3).

Discussion
Maternal GWG is a natural physiologically progressive process that re ects adaptive changes in normal pregnancy. [12,13] However, the disturbance of this normal physiological phenomena has been correlated with adverse maternal and neonatal clinical outcomes whether by excessive or reduced maternal GWG. [14] The results of the current study suggest that not achieving the normal GWG is associated with multiple deleterious maternal and neonatal consequences including hypertensive disease of pregnancy, gestational diabetes, rates of induced labor, failure of induced labor, cesarean delivery, neonates that are small for gestational age, preterm birth, macrosomia, and shoulder dystocia.
In agreement with our ndings, many studies have found that GWG above the IOM recommendations is associated with large for gestational age (LGA) neonates and fetal macrosomia. Conversely, GWG below the IOM recommendations has been associated with small-for-gestational-age neonates. [15,16] In addition, several studies have recognized the relationship between low GWG and preterm birth. [17,18] Hannaford and colleagues conducted a prospective cohort study including singleton, non-anomalous fetuses to evaluate perinatal outcomes in patients who gained weight below or above the IOM's recommendations, and found that women who gained weight below the IOM recommendations were 2.5 times more likely to deliver SGA neonates, and twice as likely to deliver preterm. [19] An association between excess GWG and cesarean delivery and induced labor is plausible. Excess GWG is associated with a higher incidence of LGA neonates and fetal macrosomia, and hence, a higher incidence of labor induction and cesarean delivery. This relationship has been evaluated previously by Maier and colleagues, who studied weight gain in pregnancy and its association with birthing complications among 591 women. They found that women with more GWG were at a higher risk for induced labor (55.0% vs. 45.7%, p = 0.007), signi cantly higher rates of secondary cesarean section (22.4% vs. 15.4%), and decreased chances of spontaneous vaginal birth (57.5% vs. 61.4%; p = 0.008). [20] Associations between excessive GWG and gestational diabetes as well as hypertensive disorders have been reported, but the evidence for these associations is limited. [21] A positive correlation between excess gestational weight gain and GDM was reported in a recent prospective cohort study that included 565 pregnant women; [22] the investigators found that pre-pregnancy obesity and excessive GWG during the rst and second trimesters of pregnancy may increase the risk of GDM. However, a meta-analysis conducted by Brunner and co-workers found no evidence for an effect of GWG on GDM contingent on maternal pre-pregnancy BMI category. [23] These con icting opinions may be related to the use of total GWG as the exposure variable rather than weight gain until the time of diagnosis of GDM, because the management of GDM includes dietary control and efforts to control weight gain. [10] Likewise, there is a lack of evidence to support the notion that GWG is associated with gestational hypertension and preeclampsia. [24] It is well-known that preeclampsia is associated with vascular permeability and reduced plasma oncotic pressure, and hence rapid weight gain. Nonetheless, it is di cult to ascertain whether excessive GWG is a cause or effect of preeclampsia. [25] The strengths of our study include the large sample size and the assessment of multiple maternal and neonatal outcomes. However, there are several potential limitations to our study. First, we used the total GWG at delivery; this method is hypothetical and could differ from actual measurements. Second, pre-pregnancy BMI estimation is often self-managed and not performed by a healthcare professional, and as such a bias of under-or overestimation to an unknown degree is possible. Third, our study was conducted among women delivering in Saudi Arabia only.
In conclusion, our study has found that GWG both above and below the recommendations of the IOM guidelines have adverse maternal and neonatal consequences. However, racial and ethnic differences should be considered in future research studies, as they could in uence the impact on GWG on clinical adverse outcomes.  a Odds ratio were adjusted to maternal age, pre-pregnancy BMI, prior delivery type, smoking and GA at delivery b The denominator for the shoulder dystocia outcome varies from the total sample size because it was limited to women with vaginal deliveries (n=2208 below; n=2863 within; n=4813 above). P value< 0.05 is signi cant.