Keywords: Pregnancy, Excessive gestational weight gain, Gestational BMI, Obesity and overweight, Perinatal outcomes.

Abstract

The altered BMI in women during pregnancy generates problems in perinatal results that harm the newborn as well as the mother herself. The study of the relationship between perinatal outcomes and altered BMI in pregnant women is a research area of growing interest, which has begun to be studied in the last two decades.

What is the available scientific evidence about body mass index in pregnant women and its perinatal effects?

Systematize the available and accessible medical literature on body mass index in pregnant women and its perinatal effects.

A systematic review of perinatal outcomes and their maternal-fetal effect was carried out. Nine scientific articles were included through the PUBMED metasearch engine, not including duplicate studies and published outside the study and search period, studies with poor methodological quality after applying the STROBE tool.

It was shown that obese and overweight pregnant women have a higher risk of cesarean delivery, fetal macrosomia in the newborn, and gestational diabetes. Pregnant women with excessive gestational weight gain according to IOM recommendations have a threefold risk of presenting preeclampsia and other fatal complications

There is a relationship between perinatal outcomes and the body mass index of pregnant women and it is extremely important to create strategies that reduce poor perinatal outcomes associated with an altered BMI during pregnancy.

INTRODUCTION: CURRENT STATUS OF THE TOPIC

Pregnancy is one of the most vulnerable stages in the life of women, in addition to having to go through the different phases of this biological period, incurs a nutritional risk due to the physiological changes of pregnancy, where there is an important anabolic activity that institutes an increase in maternal nutritional needs of almost all nutrients since the fetus develops at the expense of the mother. Among all these changes, weight gain caused by multiple factors such as the presence of the growing fetus, fluid retention, increased body fat, and increased uterine muscle mass stands out (Maldonado et al., 2008).

The recommended weight gain varies depending on the mother’s pre-gestational Body Mass Index (BMI), with greater weight gain in women with a low or normal BMI before conception than in overweight or obese women (Minjarez et al., 2014). Gestational weight gain (GPG) is a complicated phenomenon influenced not only by maternal physiological and metabolic changes but also by placental metabolism. In recent years, the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) have proposed assessing the nutritional status of pregnant women using BMI, which is obtained by dividing the value of weight (kg) by that of height (m) squared.

Ramos et al. (2021) classify the increase in BMI into obesity and overweight, the first being body mass index (BMI) > 30 kg/m2 and overweight as a BMI of 25.0 to 29.9 kg/m2. The recommendations that are currently most accepted are those indicated by the IOM (Institute of Medicine of the USA), for weight gain about BMI before pregnancy (pre-BMI), in this way a pregnant woman with BMI in normal ranges should increase 11.5-16.0 kg, if she were overweight the increase should be between 7.0-11.5 kg and in obesity only 6 kg. Therefore, the increase in pre-BMI is related to obstetric events during pregnancy that can transcend after childbirth, Ramos et al. (2021, p.2) mention that among the main ones we can find: gestational diabetes (GDM), hypertensive disease, thromboembolic complications, cancer and adverse obstetric events (spontaneous abortion, infection, hemorrhages, anesthesia risks). In this way, we can say that the Body Mass Index associated with pregnancy has shown a good partnership with the degree of adiposity and with the risk of chronic non-communicable diseases such as gestational diabetes, and preeclampsia. macrosomia, prolonged deliveries, and higher rates of cesarean sections.

The above, objective of this research is to convey and emphasize the importance of the increase in BMI during pregnancy and its association with perinatal outcomes because most of the authors who have researched the subject conclude that maternal obesity contributes significantly to a worse prognosis for the mother and newborn during childbirth and in the immediate puerperium. The articles included in this systematic review agree that this increased risk is directly proportional and more severe to weight gain during pregnancy (De la Plata et al. 2018).

CLINICAL QUESTION and VARIABLES(PICO)

What is the available scientific evidence about body mass index in pregnant women and its perinatal effects? The PICO variables are broken down in the question posed above, which will govern the course of this review, which are below:

P-OBLATION: Pregnant women with altered BMI

I-INTERVENTION: Body Mass Index

C-OMPARISON: -------------------------

O-UTOCOME/RESULTS: Perinatal effects

MATERIAL AND METHODS:

Type of Study

The present research has a qualitative approach, its design being a systematic prognostic review.

Literature search

The study period was the last 20 years (2000-2020) and the search period was between August 1 and August 30, 2020. The source of information was the scientific articles included in the review, therefore, the inclusion criteria were the scientific articles that address the influence of body mass index in pregnant women and its perinatal effects, scientific articles with observational, descriptive, cross-sectional methodological design, analytical cohort, and case-control studies, scientific articles with good methodological quality fulfilling the items of the tool STROBE and PRISMA. On the other hand, the exclusion criteria were specific studies that could not be applied in the areas of health, duplicate studies, and studies published outside the desired period and search period.

Frame 1

DeSC and MeSH descriptors used

The bibliographic search strategies were carried out through four steps: a) the identification of the search terms (thesauri), through the use of DeSC (descriptors of health science) where the PICO variables were introduced for the identification of the thesauri that were used in the search process; b) checking the similarities of the DeSC and MeSH descriptors, verifying the number of the identifying IDs in both (see table); (c) the construction and definition of the search string, using the logical or boolean (DNA) operative; d) and the application of search strategies, where for this systematic review, the specific MeSH descriptors were used for the search that, in the first instance, was carried out independently for each of the MeSH terms and then with them combined (Table 1).

The limits or filters established for the search strategy were the following: Studies carried out in humans, female sex, and adult patients, Publications in English and Spanish, Published in the last 20 years, where 200 articles were identified through the use of the PRISMA diagram included a total of 9 scientific articles for this review. (Figure 1).

Figure 1

PRISMA flowchart: Search strategy, selection process, and exclusion of studies included in this systematic review

Source: Adapted from the guide of methodological aspects to be evaluated in a systematic review, UNICA (2020).

RESULTS AND DISCUSSION: SUMMARY OF EVIDENCE:

The articles taken for this review showed differences in certain concepts, constructs, objectives, and methods used. To give homogeneity to the evidence presented, the studies were grouped into sections related to the main variables studied, in terms of perinatal outcomes associated with altered BMI in pregnant women. The sections used to summarize the perinatal outcomes associated with altered BMI in pregnant women were: overweight, obese, and underweight women during pregnancy, as they are at risk of being large for gestational age newborn, emergency cesarean delivery, labor induction number, and fetal macrosomia (>4,250 grams). The only maternal risk factor reported and associated with overweight and obesity was the risk of Hypertension and Gestational Diabetes.

Because of the purpose of this review, the description of the results of the articles included in each section includes the most outstanding methodological aspects, as well as the main findings of the studies, exclusively about perinatal outcomes concerning altered BMI in pregnant women (Table 1).

Table 1

Table-summary of the results of the bibliographic search

Some articles also included other study variables; These have not been collected because they do not constitute the objective of this work. It should be noted that the United States represented the country with the largest scientific publications related to the subject, it is said that this could be explained by the lifestyle of the American population since this country has a high rate of obesity in its population and that is why the concern of the health system to investigate this association, is due to the above. The year 2015 and 2017 with 22.2% (n=2) respectively, were the years in which the most frequently published research addressing the relationship between maternal BMI and perinatal effects, followed by 2004, 2006, 2009, 2016, 2018, with 11.1% (n=1) respectively (Table 1.1).

55.5% (n=5) of the articles were published in English, followed by English-Chinese with 33.3% (n=3), and in third place Spanish with 11.1% (n=1). The language of scientific publication disclosed in the journals is the English language, in our review it accounted for 56% of the articles (five articles) included in this review, so we reiterate the importance for health personnel to know and understand the English language to keep up with new medical advances.

Table 1.1

Table-summary of the results of the bibliographic search

55.5% (n=5) of the articles were published in English (Table 1). The language of scientific publication published in the journals is the English language, in this review, it accounted for 56% of the articles (five articles) included, so we reiterate the importance for health personnel to know and understand the English language to keep up with new medical advances. Three out of nine scientific articles were found, which took into account the alteration of the body mass index and its classification according to the WHO and the perinatal effects that this brings. Tables 1 and 1.1 show that only one article, which was conducted by Zhao et al (2017) studied the association of low maternal weight and perinatal effects, finding that this represents a lower risk for emergency cesarean delivery in underweight pregnant women, compared to the risk reported for overweight and obese pregnant women.

Tabla 2

Perinatal results found in scientific articles

Note: ID: Identification of the item, which corresponds to the number assigned to the item during the selection process.

Source: Articles included in this review.

In the three articles that reported more neonatal than fetal risk factors (Table 2.1), it was reported that the following neonatal risk factors associated with obesity and overweight are: large for gestational age newborn, emergency cesarean delivery, labor induction number, and fetal macrosomia (>4,250 grams). The only maternal risk factor reported and associated with overweight and obesity was the risk of hypertension and gestational diabetes. The fact that most studies reported the perinatal effect of obesity and maternal overweight may be closely related to the fact that, in daily clinical practice, it is more evident to observe overweight or obese patients than underweight.

Table 2.1

Perinatal outcomes according to Alteration of maternal BMI during gestation identified in the included articles

Note: OR: Obbs Ratio, also known as odds ratio, is a risk measure used to express a causal association between two or more variables, It is considered a risk factor if the OR is greater than one if it is less than one it is considered a protective factor.

Source: Articles included in this review.

Table 2.2.

Perinatal results according to Gestational Weight Gain according to IOM recommendations during gestation identified in the included articles

Note: OR: Obbs Ratio, also known as odds ratio, is a risk measure used to express a causal association between two or more variables, It is considered a risk factor if the OR is greater than one if it is less than one it is considered a protective factor.

Source: Articles included in this review.

Gestational weight gain above what is recommended according to IOM guidelines was a risk factor for cesarean section in four of the five articles in which this relationship was studied. The risk of hypertensive disease of pregnancy (Preeclampsia, Gestational hypertension) was three times higher compared to the 38 pregnant women who presented a minimal or lower increase than recommended, the risk of Fetal Macrosomia was two to three times higher in pregnant women with an excessive increase, compared to pregnant women with minimal increase. Excessive weight gain as recommended by the IOM guidelines was also a risk factor for Shoulder Dystocia and NICU admission, it is worth mentioning that it was a protective factor for preterm birth and small for gestational age newborns.

Pregnancy weight gain below the recommended IOM guidelines was a risk factor for preterm birth in three of the four articles where this association was reported. Newborn small for gestational age, reported in three articles of which one reported to be a protective factor with an OR 0.6. Acute respiratory disease reported in an article with an OR: 5, was not a protective factor for newborns large for gestational age, instrumental delivery, the risk of cesarean section, was not significant concerning minimal or excessive weight gain, gestational weight gain below recommended also posed a risk factor for low birth weight, placental abruption, gestational diabetes. The increase in gestational weight below that recommended according to the IOM guidelines was a protective factor for fetal macrosomia identified in three articles and reported only in one article with an OR: 0.60, hypertensive disorders (preeclampsia, gestational hypertension) was a protective factor in four of the articles. (Table 2.2)

On the other hand, the minimum gestational weight gain recommended according to the IOM guidelines was a risk factor for Small Gestational Age Newborns (SGA) with an OR: 1.55, it was identified that cesarean delivery did not present significant differences when compared with pregnant women who presented a weight gain below the recommended. It is worth mentioning that the minimum gestational weight gain was not studied in seven articles of the nine, possibly this is because the impact it has on the clinical outcome of pregnancy presents certain similarities with weight gain below that recommended by the IOM. (Table 2.2)

CONCLUSION AND RECOMMENDATIONS (GRADE)

As a conclusion of this systematic review article, we identified the relationship between body mass index before and during pregnancy with the perinatal effects that the baby or mother in question may have. Mothers who were overweight or obese had a higher association of hypertensive disorders (pre-eclampsia, gestational hypertension), having a large-for-gestational-age baby (macrosomia), increased chances of emergency cesarean delivery, or having gestational diabetes. It should be noted that, although pregnant women have minimal or below IOM recommendations, they will have a higher risk of premature birth, newborn babies small for gestational age, acute respiratory diseases, low birth weight (LBW), placental abruption, gestational diabetes, and neonatal hypoglycemia.

DECLARATION OF INTERESTS

Conflict of interest

The authors have declared that they have no conflict of interest, Source of funding: none.

Ethical approval

No ethical approval was required as this is a secondary analysis of data derived from published primary studies.

AUTHORS’ CONTRIBUTION

Renaldy ESPINOZA-SOTELO preparation first and latest version of the article, data extraction, searching, study identification.

Alexis, AGUILAR-MEZA: protocol development and research report, data extraction, searches, study identification.

Fernanda PINEDA-GEA: evaluation of the quality of data extraction, searches, study identification, data extraction, and preparation of the first and last version of the manuscript for review.

René GUTIERRÉZ-ABURTO: preparation of the manuscript for review.

All authors have reviewed and approved the final version of the text.