In this analysis of 88,297 singleton pregnancies, we found associations between not achieving gestational weight gain goals recommended by IOM and several adverse maternal and neonatal outcomes including cesarean birth, PROM, PIH, postpartum hemorrhage, PTB, LGA, SGA, macrosomia, fetal distress and newborn asphyxia.
Our findings corresponds to other studies including a recent meta analysis of GWG and pregnancy outcomes that included 1,309,136 women.1 Specifically, the study showed that insufficient GWG was related to SGA (OR 1.53, 95%CI 1.44-1.64) and preterm birth (OR 1.70, 95%CI 1.32-2.20), whereas excessive GWG was associated with LGA (OR 1.85, 95%CI 1.76-1.95), macrosomia (OR 1.95, 95%CI 1.79-2.11), and cesarean birth (OR 1.30, 95%CI 1.25-1.35). A similar study from the US including 29,861 pregnancies also evaluated the relationship between excessive GWG and PIH (aOR 1.84, 95%CI 1.66-2.04), the prevalence of GDM in the total population was 6.2%.16 However, we found in our study that the impact of excessive GWG on the risk of PIH in Chinese seems to be larger than in the Westerners (aOR 2.44, 95%CI 2.26-2.64), and the prevalence of GDM was 12.7%. Although it is not possible to perform statistical comparison based on these figures. As it is well known that body fat percentage in Chinese is higher than that in Caucasian at the same GWG category, the metabolic mechanism leading to PIH and GDM may manifest that a lower cutoff at 24 kg/m2 for defining overweight and 28 kg/m2 for defining obese in Chinese would be more applicable for risk assessment.
In addition to common perinatal outcomes associated with poor GWG control and well described in previous studies, we also explored the possible relationship with premature rupture of membrane (PROM) and placenta abruption. In particular, inadequate GWG was associated with higher risk in PROM (aOR 1.15, 95%CI 1.11-1.20) and placenta abruption (aOR 1.54, 95%CI 1.29-1.85), indicating that nutritional factors or underlying social economic factors may play a role in the pathogenesis of these conditions.30 Considerably fewer studies have evaluated the specific correlation between GWG and preterm birth subgroup (medically-indicated PTB, PPROM and sPTB without PROM) and gestational week distribution.31,32,33 In our study, we found that excessive GWG had greater influence on total PTB than insufficient GWG (aOR 1.48, 95%CI 1.38-1.58 vs aOR 1.22, 95%CI 1.15-1.29), with highest odds ratio in medically-indicated PTB subgroup (aOR 2.04, 95%CI 1.82-2.29), while insufficient GWG had highest odds ratio in PPROM subgroup (aOR 1.35, 95%CI 1.21-1.50), and among gestational weeks between 24 and 28 (aOR 3.28, 95%CI 2.19-4.90). Such findings is different from similar population based studies from developed countries but supports study from middle income countries.1,5,34
Studies testifying IOM recommendations among Chinese have reached inconclusive results,23,35,36 Single site study including 4,736 term pregnancies using the WHO BMI cut-off points, concluded that IOM GWG recommendations are appropriate for Chinese women.23 While study carried out in Hong Kong including 754 pregnancies with complete anthropometry data,35 found that the IOM recommended weight gain ranges are narrower than observed. However, larger cohort study encompassing 13,717 pregnancies with optimal outcomes conducted in a Middle-South city of China revealed that the IOM recommended GWG ranges are still within the middle 70% of Chinese GWG distributions.36 In a recently published follow-up study including 34,288 pregnancies,37 the author managed to develop GWG charts of Chinese women based on the same BMI classification system in our study, and found that the IOM recommended ranges fell within the 25th and 75th percentiles for underweight and normal weight women but fell below the 50th percentile for overweight and obese women. Neither aforementioned studies included data relating to postpartum outcomes. Elevating the upper limit of the GWG ranges may lead to long-term adverse outcomes, including postpartum weight retention childhood obesity, and adolescent cardiometabolic risk. 38,39,40,41 Nonetheless, a meta-analysis of Westerners from 25 pooled cohort studies including 196,670 participants revealed that GWG ranges associated with the lowest risks for any adverse outcome were roughly comparable with the IOM ranges for underweight, normal weight, and overweight, and were lower for all obesity grades.42
A cohort study, the INTERGROWTH-21st Project,43 reported that the weight gain pattern in normal weight women who came from eight geographically diverse urban areas, including China, was strikingly similar, indicates that separate GWG charts for women from different racial groups are not necessary. The researchers speculating that the racial differences reported are more likely caused by social economical or lifestyle factors than true biological differences in nutrient absorption among uncomplicated women.44,45,46 Until now, the IOM recommendations was well-accepted in China, Our data showed that GWG within IOM recommendations may help prevent various adverse perinatal outcomes. Given the risks of a GWG outside of the IOM recommendations, as documented in this population based study whereby only 44.1% of women achieved a optimal GWG targets. Appropriate management of GWG, by way of lifestyle instructions in diet, exercise and other health behaviours, 47 will assists in promoting maternal and neonatal health.
This study has several limitations. First, the analyses did not account for potential confounding factors, such as medical insurance type or hospital type. Second, first trimester pregnancy BMI, instead of pre-pregnancy BMI, was used to classify women. This introduces the possibility of mis-classification bias. We did not assume that women gained a standard weight during first trimester which ignored individual difference. However, it is not feasible to measure the pre-pregnancy weight in clinical practise and self-reported pre-pregnancy weight is generally unreliable. Noted strengths included prospectively designed and well defined net-work based data acquisition system with detailed information on perinatal outcomes. The sample size was the largest concerning Chinese ethics before submission and spanned the four main ecnomic zones of China and is representative. With rigorous ascertainment of outcomes and calculation of GWG to account for the duration of pregnancy. The results presented as incidence rates and adjusted odds ratio is readily for clinical counseling.