Background
Excessive gestational weight gain (EGWG) has short-, medium-, and long-term health implications for women and their children(1). Physiological weight gain occurs during pregnancy; this weight gain is reported as GWG and is considered normal and healthy both for the mother and the foetus; GWG is influenced by maternal and placental metabolic changes(2). However, several epidemiological studies have shown that obesity, overweight, and EGWG in women are associated with increased risks of macrosomic deliveries(3-5), shoulder dystocia, meconium aspiration, neonatal hypoglycaemia(6), caesarean deliveries(5-7), gestational diabetes(8,9), postpartum weight retention(10,11), pre-eclampsia(5,11), cardiometabolic sequelae(12), and fetal and infant death(13).
Furthermore, excessive maternal weight gain has been linked to an increased risk of childhood obesity and other components of metabolic syndrome(13). The Institute of Medicine (IOM) reviewed GWG standards in 2009 and recommended that women with higher pregestational BMI should have lower GWG, particularly those with an initial pregnancy BMI of 30 kg/m2 or more(13). In Mexico, in 2012 the standards of care for pregnant women were reviewed regarding gestational weight gain; however, guidelines were published as recently as 2016(14).
The current IOM recommendations for GWG are as follows: low-weight women (BMI < 18.5 kg/m2): weight gain of 13-18 kg; normal-weight women (BMI = 18.5-24.9 kg/m2): 11-16 kg; overweight women (BMI = 25.0-29.9 kg/m2): 7-11 kg; and obese women (BMI > 30 kg/m2): 5-9 kg(13). However, the Centers for Disease Control and Prevention reported an EGWG prevalence of 47.5% across 46 US states, New York City, and the District of Columbia during 2012-2013; they also reported that only 32.1% of pregnant women met the IOM recommendations(15).
Early prenatal care, the development of a meal plan, and exercise are crucial for avoiding excessive weight gain in pregnant women, thus reducing the risks of obesity, morbidity, and mortality in their offspring(1). A recent systematic review and meta-analysis showed that an intensive lifestyle intervention during pregnancy results in reduced EGWG, decreasing the likelihood of large-for-gestational-age newborns(16).
According to the health authorities of Mexico, approximately 75.6 % of women of reproductive age (between 20 and 49 years) are obese or overweight(17). A study conducted in 2010 found a prevalence of 38% of EGWG applying the IOM recommendations(18). However, based on our literature review, we have not found recent studies investigating the prevalence of EGWG in different regions in Mexico. Thus, this study estimated the prevalence of EGWG among pregnant women residing in Tijuana who attended the Mexican Social Security Institute. In addition, the study assessed the factors and outcomes associated with it.
Methods
Pregnant women who delivered in Hospital #7 between October 1st 2016 to January 31st 2017, in immediate puerperium (first 24 hours after delivery), with a single delivery and live single birth, who started prenatal control between the 6th or 8th weeks of gestation, with a minimum of 8 total visits, including baseline laboratory and weight measurement were included. Women having an abortion, an embryonic pregnancy, or trophoblastic disease, those with incomplete newborn or pregnancy records, and those who gave birth to infants with congenital malformations were excluded. The Ethics Committee of Medical and Psychology Schools of Universidad Autonoma de Baja California provided approval for this study on 25th August, 2016. Prior to patients' discharge, data from the medical records of women in immediate puerperium was retrieved. Any information missing from the medical records was obtained directly from the patient, and patients provided verbal consent.
Data from the medical records was captured using Statistical Package for the Social Sciences (SPSS). BMI was categorised according to the World Health Organization classification, and EGWG was determined using the IOM guidelines(13). Descriptive statistics were calculated for numerical variables and were assessed for normality using the Shapiro- Wilks test. The prevalence of EGWG was estimated in analyses stratified by BMI categories and neonatal weight categories. Associations between EGWG and maternal and newborn variables were assessed using binomial or multinomial regression analysis. The variables included in the analyses were smoking history, alcohol and drug use, hypertension, diabetes mellitus, gestational diabetes, preeclampsia and other diseases in previous pregnancies, number of pregnancies, miscarriages, presence of sexually transmitted diseases, BMI category, threatened miscarriage, type of delivery, premature rupture of membranes, preterm premature rupture of membranes, amniotic fluid, birth weight, and neonatal complications. An independent sample t test was used for the comparison of means between patients with EGWG and those without EGWG; for the comparison of means among more than two groups (i.e., BMI categories), we used one-factor analysis of variance or Kruskal-Wallis H test if the data were not normally distributed.
Results
A total of 438 women were included in this study. The mean GWG was 12.77 kg (SD = 6.33 kg); other descriptive statistics are shown in Table 1.
BMI category | N (%) | Age, years mean (SD) | GWG, kg mean (SD) | EGWG, % | Risk of EGWG OR (95% CI) P | EGWG above maximum recommendeda, kg mean (SD) | Macrosomic delivery, % |
---|---|---|---|---|---|---|---|
Underweight | 13 (3) | 22 (3.5) | 15.2 (5.3) | 21.4 | 0.73 (0.19-2.76) 0.64 | 4.33 (1.52) | 0 |
Normal | 161(37) | 25 (5.2) | 13.8 (6.2) | 29.4 | 1 | 5.15 (5.26) | 11.2 |
Overweight | 157(36) | 26 (5.4) | 12.1 (5.4) | 47.8 | 22.2 (1.40-3.52) 0.001 | 5.46 (4.12) | 6.4 |
Obese | 106(24) | 29 (5.0) | 11.8 (5.9) | 59.4 | 3.55 (2.12-5.95) 0.0001 | 6.35 (4.46) | 14.4 |
TOTAL | 437(100) | 25.5 (5.5) | 12.4 (6.3) | 43.0 | 5.66 (4.52) | 9.9 |
GWG: Gestational Weight Gain; EGWG: Excess Gestational Weight Gain.
aOnly women with EGWG were included in this analysis.
The GWG means for different BMI categories (shown in Table 1) were inversely proportional to BMI. However, when the IOM criteria(13) for EGWG were applied, we found an overall prevalence of EGWG of 43%, demonstrating a higher prevalence of EGWG in women with higher BMI (Table 1; OR = 2.73, 95% CI = 1.81-4.11, for BMI < 24.9 vs BMI > 25). No significant difference was observed in the amount of weight gained above the maximum IOM standards among the BMI categories (Kruskal-Wallis test; χ2df = 3 = 3.9, p = 0.27).
Significant dependence was found between EGWG and newborn weight categories (χ2df = 3 = 8.4, p = 0.038), and in analysis stratified by newborn variables (macrosomic delivery vs non-macrosomic delivery), an association was observed (Table 2).
Birth weight | OR (CI 95%) | p |
---|---|---|
<2500 g | 1.2 (0.5-4.2) | 0.65 |
2500-4000 g | 1 | |
>4000 g | 2.2 (1.2-4.2) | 0.017 |
Macrosomia | ||
> 4000 g | 2.2 (1.2-4.2) | 0.017 |
>4000 g adjusted for gestational diabetes and diabetes mellitus type 2 | 2.1 (1.1-4.1) | 0.022 |
< 4000 g | 1 | |
Threatened miscarriage | ||
threatened miscarriage | 2.2 (1.1-4.5) | 0.037 |
TM adjusted for previous abortion, alcohol abuse, and maternal underweight | 2.8 (1.3-6.1) |
0.009 |
No miscarriage | 1 |
Moreover, 7.7% of patients had a threatened miscarriage (TM) during the pregnancy course, and compared with adequate GWG women with excessive GWG had higher risk of TM, when adjusted for previous abortion, alcohol abuse, and maternal underweight, excessive GWG was associated with an increased risk of TM (Table 2).
Discussion
In this study, we found an overall prevalence of EGWG of 43%, which is significantly higher than the 38% previously reported in Mexico(18). We also found a higher prevalence of EGWG in women with higher BMI (overweight and obesity). Since the prevalence of obesity in women has increased by 5.4% from 2012 to 2016 in Mexico(19) , and the higher the BMI the higher the EGWG it might be expected an increase during the following years. No difference was observed in the amount of weight gained above the maximum IOM standards among the BMI categories. An association was observed between EGWG and macrosomic delivery, which is consistent with previous reports(20-22).
An association was observed between EGWG and TM. Because of the cross-sectional study design, a causal effect could not be established. We did not find any association between BMI (BMI > 24.9 kg/m2) and the threat of miscarriage, consistent with the findings of a metaanalysis conducted in 2008(23) and other studies(24,25).
Contrary to other studies we did not find an association between EGWG and younger maternal age(26) low Apgar score (27), or preterm birth(28). This finding might be attributed to the small sample of patients with those particular conditions and the exclusion of women with abortion.
The limitations of the study include significant recall bias in patients who had missing information from their medical records, especially regarding the date of last menstrual period (used to determine gestational age) and pregestational weight (baseline weight), because these data were self-reported in some cases. Another limitation may be the use of non-standardised scales and weighting techniques among different hospital staff members, without proper weighting in follow-up and prenatal consults. Both weighting and formalised exercise prescription have been shown to lead to reduced GWG and thus a significantly lower prevalence of EGWG(29). In addition, the exclusion of women with EGWG who had miscarriages might have led to an underestimation of the prevalence of EGWG. Women with an abortion experience were not assessed because the study only included women with a live newborn child.
However, the strengths of this study are the large number of participants, the fact that this is the second study published specifically regarding the north-western region of México, the unique location of Tijuana as a Mexico-US border city, with the highest prevalence of obesity in children aged 6-11 years(19), and the fact that pregnant women were recruited from the largest and best organised public health institution in Mexico.
Conclusions
This study revealed a very high prevalence of EGWG (43%) among pregnant women residing in Tijuana. Those with EGWG had a higher likelihood of having macrosomic newborns. This study also found an association between EGWG and TM. EGWG was seen more often in patients with pre-pregnancy overweight and obese BMI. No association was observed linking EGWG to maternal diabetes mellitus, hypertension, drug abuse, alcohol abuse, or underweight BMI.
These results outline the importance of performing close surveillance and care to all pregnant women to prevent EGWG. Women who are overweight or obese might benefit from a more specialized prenatal control.
Declarations
Ethics approval and consent to participate
The Ethics Committee of Medical and Psychology Schools of Universidad Autonoma de Baja California reviewed and provided approval for this study. Any information missing from the medical records was obtained directly from the patient, and patients provided verbal consent.