# Clinical Observation of Effects of Prepregnancy Body Mass Index and Weight Gain during Pregnancy on Neonatal Weight and Delivery Outcome

Authors: Yan Jin; Xiwang Dai; Nan Wang; Yaowei Hu; Limei Quan; Shuli Zhu
Journal: Evidence-Based Complementary and Alternative Medicine
 (2021)

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## Abstract

Objective. The increase of BMI before pregnancy and during pregnancy will lead to hypertensive disorder in pregnancy (HDP) and abnormal glycolipid metabolism, as well as increase the risk of neonatal weight abnormalities and adverse pregnancy outcome. This study retrospectively analyzed the clinical data of 358 women who were admitted to the obstetrics department of our hospital from January 2018 to July 2019. And the relationship between prepregnancy BMI, BMI increase during pregnancy and delivery methods, postpartum hemorrhage, neonatal weight, premature delivery, neonatal asphyxia, gestational diabetes mellitus (GDM), and hypertension during pregnancy (HDP) was observed and compared. The results show that both high BMI before pregnancy and excessive weight gain during pregnancy can lead to the incidence of abnormal birth weight and adverse birth outcome increase. Therefore, in order to reduce the incidence of neonatal weight abnormalities and adverse birth outcomes and to prevent the adverse effects during pregnancy and postpartum, clinically, obese women should be guided to eat according to reasonable diet and exercise to control their weight.


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## Body

## 1. Introduction

Since pregnant women need to satisfy fetal growth and lactation, the maternal weight would increase with the pregnancy process going on. Therefore, weight measurement is the necessary part in pregnancy tests [1]. In fact, abnormal weight gain has adverse effects for both matrix and fetus [2, 3]. In clinical practice, body mass index (BMI) and weight gain during pregnancy are used for measuring maternal nutritional conditions and fetal growth [4]. In recent years, the increase of BMI before pregnancy and during pregnancy increases significantly, which results in an increased incidence of hypertensive disorder in pregnancy (HDP) and abnormal glucose and lipid metabolism and affects the growth and gestational age of the fetus [5–7]. The purpose of the study is to analyze the relationship between BMI of pregnant women before pregnancy, weight gain during pregnancy, and neonatal weight and delivery outcome to provide scientific reference for clinical perinatal healthcare of the parturient.


## 2. Data and Methodology

### 2.1. General Information

The clinical data of 358 puerperal women in our hospital from January 2019 to July 2021 were retrospectively analyzed, and the average age, average gestation period, average weight, and height are seen in Table1.Table 1
General information and grouping of pregnant women.
General information (x¯ ± s)BMI grouping before pregnancy (n)Grouping of increased BMI during pregnancy (n)The total number of parturients (n = 358)The average age: 29.84 ± 3.16 yearsNormal group (n = 243)Deficient increase group (n = 103)The average gestation period: 37.12 ± 3.46 weeksOverweight group (n = 76)Appropriate increase group (n = 197)The average weight: 61.22 ± 10.41 kgObese group (n = 39)Excessive increase group (n = 58)The average height: 158.24 ± 7.45 cm——


### 2.2. Inclusion Criteria

The inclusion criteria were as follows: (i) pregnant women aged from 18 to 40, gestation period in 32 to 42 weeks, primipara, and singleton cases; (ii) ultrasound examination passed, umbilical cord not entangled, and amniotic fluid in good condition.


### 2.3. Data Exclusion Criteria

The exclusion criteria were as follows: (i) multiple pregnancy, (ii) placenta previa, (iii) placental abruption, (iv) cesarean delivery due to society reasons and lack of information cases, and (v) women with advanced maternal age.


### 2.4. Methodology

Firstly, height (m) and weight (kg) of pregnant women were, respectively, applied to calculate BMI before pregnancy and delivery. BMI (kg/m2) = weight (kg)/height2 (m2). According to BMI before pregnancy, the patients were divided into 3 groups: (1) a total of 243 cases with BMI <24.0 kg/m2 were classified as the normal group, (2) a total of 76 cases with 24.0 kg/m2 ≤ BMI < 28.0 kg/m2 were classified as the overweight group, and (3) a total of 39 cases with BMI ≥28.0 kg/m2 were classified as the obese group. And then, the increment of BMI was calculated by subtracting BMI of prepregnancy from BMI of predelivery.According to the increment of BMI during pregnancy, they could be grouped into another three groups: (1) a total of 103 cases with increment <4 kg/m2 as the deficient increase group, (2) a total of 197 cases with 4 kg/m2 ≤ increment ≤ 6 kg/m2 as the appropriate increase group, and (3) a total of 58 cases with increment >6 kg/m2 as the excessive increase group. In addition, gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy (HDP), delivery modes, postpartum hemorrhage, neonatal weight, asphyxia neonatorum, and other situations were recorded.


### 2.5. Index Observation and Measurement

Prepregnancy BMI and increment of BMI with delivery modes, postpartum hemorrhage, and delivery outcome were recorded and compared to analyze the relationship between them. The relevance was recorded and found out by comparing prepregnancy BMI and increment of BMI with neonatal weight, premature delivery, and other situations.Measurement of HDP [8]: blood pressure increase occurred firstly after 20 weeks of delivery. Measurement of GDM [9]: 75 g oral glucose tolerance test results: fasting blood glucose >5.1 mmol/L, 1 h blood glucose >10.0 mmol/L, and 2 h blood glucose >8.5 mmol/L. Among them, any increase in the result can be diagnosed as GDM.Measurement of postpartum hemorrhage [10]: postpartum bleeding volume >500 ml. Criteria of neonatal weight: low-weight infants <2500 g, normal-weight infants from 2500 g to 4000 g, and macrosomia infants ≥4000 g. Measurement of premature delivery: gestation less than 37 weeks. Measurement of asphyxia neonatorum: Apgar score <7 in 1 minute.


### 2.6. Statistical Analysis

All data were processed with SPSS 22.0 statistical software, and GraphPad Prism 8 was used to make statistical graphs. Measurement data were expressed as mean ± standard deviation (x¯ ± s), an independent sample t-test was used for comparison between groups, count data were expressed as n (%), and chi-square (χ2) test was performed. The difference was statistically significant when P<0.05.


## 2.1. General Information

The clinical data of 358 puerperal women in our hospital from January 2019 to July 2021 were retrospectively analyzed, and the average age, average gestation period, average weight, and height are seen in Table1.Table 1
General information and grouping of pregnant women.
General information (x¯ ± s)BMI grouping before pregnancy (n)Grouping of increased BMI during pregnancy (n)The total number of parturients (n = 358)The average age: 29.84 ± 3.16 yearsNormal group (n = 243)Deficient increase group (n = 103)The average gestation period: 37.12 ± 3.46 weeksOverweight group (n = 76)Appropriate increase group (n = 197)The average weight: 61.22 ± 10.41 kgObese group (n = 39)Excessive increase group (n = 58)The average height: 158.24 ± 7.45 cm——


## 2.2. Inclusion Criteria

The inclusion criteria were as follows: (i) pregnant women aged from 18 to 40, gestation period in 32 to 42 weeks, primipara, and singleton cases; (ii) ultrasound examination passed, umbilical cord not entangled, and amniotic fluid in good condition.


## 2.3. Data Exclusion Criteria

The exclusion criteria were as follows: (i) multiple pregnancy, (ii) placenta previa, (iii) placental abruption, (iv) cesarean delivery due to society reasons and lack of information cases, and (v) women with advanced maternal age.


## 2.4. Methodology

Firstly, height (m) and weight (kg) of pregnant women were, respectively, applied to calculate BMI before pregnancy and delivery. BMI (kg/m2) = weight (kg)/height2 (m2). According to BMI before pregnancy, the patients were divided into 3 groups: (1) a total of 243 cases with BMI <24.0 kg/m2 were classified as the normal group, (2) a total of 76 cases with 24.0 kg/m2 ≤ BMI < 28.0 kg/m2 were classified as the overweight group, and (3) a total of 39 cases with BMI ≥28.0 kg/m2 were classified as the obese group. And then, the increment of BMI was calculated by subtracting BMI of prepregnancy from BMI of predelivery.According to the increment of BMI during pregnancy, they could be grouped into another three groups: (1) a total of 103 cases with increment <4 kg/m2 as the deficient increase group, (2) a total of 197 cases with 4 kg/m2 ≤ increment ≤ 6 kg/m2 as the appropriate increase group, and (3) a total of 58 cases with increment >6 kg/m2 as the excessive increase group. In addition, gestational diabetes mellitus (GDM), hypertensive disorders of pregnancy (HDP), delivery modes, postpartum hemorrhage, neonatal weight, asphyxia neonatorum, and other situations were recorded.


## 2.5. Index Observation and Measurement

Prepregnancy BMI and increment of BMI with delivery modes, postpartum hemorrhage, and delivery outcome were recorded and compared to analyze the relationship between them. The relevance was recorded and found out by comparing prepregnancy BMI and increment of BMI with neonatal weight, premature delivery, and other situations.Measurement of HDP [8]: blood pressure increase occurred firstly after 20 weeks of delivery. Measurement of GDM [9]: 75 g oral glucose tolerance test results: fasting blood glucose >5.1 mmol/L, 1 h blood glucose >10.0 mmol/L, and 2 h blood glucose >8.5 mmol/L. Among them, any increase in the result can be diagnosed as GDM.Measurement of postpartum hemorrhage [10]: postpartum bleeding volume >500 ml. Criteria of neonatal weight: low-weight infants <2500 g, normal-weight infants from 2500 g to 4000 g, and macrosomia infants ≥4000 g. Measurement of premature delivery: gestation less than 37 weeks. Measurement of asphyxia neonatorum: Apgar score <7 in 1 minute.


## 2.6. Statistical Analysis

All data were processed with SPSS 22.0 statistical software, and GraphPad Prism 8 was used to make statistical graphs. Measurement data were expressed as mean ± standard deviation (x¯ ± s), an independent sample t-test was used for comparison between groups, count data were expressed as n (%), and chi-square (χ2) test was performed. The difference was statistically significant when P<0.05.


## 3. Result

### 3.1. General Information and Grouping of Pregnant Women

General information and grouping of 358 parturients are shown in Table1.


### 3.2. Comparison of the Prepregnancy BMI and Delivery Outcome

The incidences of cesarean section, postpartum hemorrhage, GDM, and HDP in the overweight/obese group were significantly higher than those in the normal group (P<0.05), and incidences in the obese group were higher than those in the overweight group. The overweight/obese groups’ natural labour rate was lower than the normal group (P<0.05), and natural labour rate in the obese group was lower than that in the overweight group (P<0.05, Table 2).Table 2
Comparison of the prepregnancy BMI and delivery outcome (n, %).
GroupCaseCesarean sectionNatural labourPostpartum hemorrhageHDPGDMNormal group243104 (42.79%)139 (57.21%)12 (4.93%)23 (9.46%)17 (6.99%)Overweight group7642 (55.26%)∗34 (44.74%)∗7 (9.21%)∗10 (13.15%)∗7 (9.21%)∗Obese group3927 (69.23%)∗#12 (30.77%)∗#6 (15.38%)∗#11 (28.20%)∗#6 (15.38%)∗#χ25.7724.5474.6626.0783.984P0.0060.0120.0160.0020.022Compared with the normal group,∗P < 0.05; compared with the overweight group, P#<0.05.


### 3.3. Comparison of the BMI Increase and Delivery Outcome

The incidences of cesarean section, postpartum hemorrhage, GDM, and HDP in the excessive increase group were significantly higher than those in the appropriate and deficient increase group, and natural labour rate in the excessive increase group was lower than that in the other groups (P<0.05, Table 3).Table 3
Comparison of the BMI increase and delivery outcome (n, %).
GroupCaseCesarean sectionNatural labourPostpartum hemorrhageHDPGDMDeficient increase group10335 (33.98%)∗68 66.02%)∗6 (5.82%)∗11 (10.67%)∗8 (7.76%)∗Appropriate increase group19796 (48.73%)∗101 (51.27%)∗11 (5.58%)∗17 (8.62%)∗13 (6.59%)∗Excessive increase group5842 (72.41%)16 (27.58%)6 (10.34%)16 (27.58%)9 (15.51%)χ26.5223.8474.1626.9883.154P0.0040.0120.0170.0020.024Compared with the excessive increase group,∗P < 0.05.


### 3.4. Comparison of the Prepregnancy BMI and Neonatal Conditions

The incidences of huge infants, premature delivery, and neonatal asphyxia in the overweight/obese group were significantly higher than those in the normal group (P<0.05), and incidences in the obese group were higher than those in the overweight group. The overweight and obese group normal neonatal weight cases were lower than the normal group (P<0.05), and normal neonatal weight cases in the obese group were lower than those in the overweight group (P<0.05, Table 4).Table 4
Comparison of the prepregnancy BMI and neonatal conditions (n, %).
GroupCaseLow neonatal weightNormal neonatal weightHuge infantsPremature deliveryNeonatal asphyxiaNormal group2434 (1.64%)231 (95.07%)8 (3.29%)22 (9.05%)20 (8.23%)Overweight group761 (1.31%)66 (86.85%)∗9 (11.84%)∗13 (17.10%)∗12 (15.78%)∗Obese group391 (2.56%)30 (76.93%)∗#8 (20.51%)∗#8 (20.51%)∗#11 (28.20%)∗#χ21.7922.5478.6625.9783.459P0.0760.0370.0010.0030.029Compared with the normal group,∗P < 0.05; compared with the overweight group, P#<0.05.


### 3.5. Comparison of the BMI Increase and Neonatal Conditions

The incidences of huge infants and neonatal asphyxia in the excessive increase group were significantly higher than those in the appropriate and deficient increase groups, and normal neonatal weight cases in the excessive increase group were lower than those in the other groups (P<0.05). The incidences of low neonatal weight and premature delivery were higher in the excessive increase and deficient increase group in comparison with the appropriate increase group (P<0.05, Table 5).Table 5
Comparison of the BMI increase and neonatal conditions (n, %).
GroupCaseLow neonatal weightNormal neonatal weightHuge infantsPremature deliveryNeonatal asphyxiaDeficient increase group1034 (3.88%)∗94 (91.27%)#5 (4.85%)#18 (17.47%)∗13 (12.62%)#Appropriate increase group1970186 (94.42%)#11 (5.58%)#16 (8.12%)18 (9.13%)#Excessive increase group582 (3.44%)∗47 (81.04%)9 (15.51%)9 (15.51%)∗12 (20.68%)χ24.9224.5479.6725.4765.884P0.0230.0270.0010.0150.013Compared with the appropriate increase group,∗P < 0.05; compared with the excessive increase group, P#<0.05.


## 3.1. General Information and Grouping of Pregnant Women

General information and grouping of 358 parturients are shown in Table1.


## 3.2. Comparison of the Prepregnancy BMI and Delivery Outcome

The incidences of cesarean section, postpartum hemorrhage, GDM, and HDP in the overweight/obese group were significantly higher than those in the normal group (P<0.05), and incidences in the obese group were higher than those in the overweight group. The overweight/obese groups’ natural labour rate was lower than the normal group (P<0.05), and natural labour rate in the obese group was lower than that in the overweight group (P<0.05, Table 2).Table 2
Comparison of the prepregnancy BMI and delivery outcome (n, %).
GroupCaseCesarean sectionNatural labourPostpartum hemorrhageHDPGDMNormal group243104 (42.79%)139 (57.21%)12 (4.93%)23 (9.46%)17 (6.99%)Overweight group7642 (55.26%)∗34 (44.74%)∗7 (9.21%)∗10 (13.15%)∗7 (9.21%)∗Obese group3927 (69.23%)∗#12 (30.77%)∗#6 (15.38%)∗#11 (28.20%)∗#6 (15.38%)∗#χ25.7724.5474.6626.0783.984P0.0060.0120.0160.0020.022Compared with the normal group,∗P < 0.05; compared with the overweight group, P#<0.05.


## 3.3. Comparison of the BMI Increase and Delivery Outcome

The incidences of cesarean section, postpartum hemorrhage, GDM, and HDP in the excessive increase group were significantly higher than those in the appropriate and deficient increase group, and natural labour rate in the excessive increase group was lower than that in the other groups (P<0.05, Table 3).Table 3
Comparison of the BMI increase and delivery outcome (n, %).
GroupCaseCesarean sectionNatural labourPostpartum hemorrhageHDPGDMDeficient increase group10335 (33.98%)∗68 66.02%)∗6 (5.82%)∗11 (10.67%)∗8 (7.76%)∗Appropriate increase group19796 (48.73%)∗101 (51.27%)∗11 (5.58%)∗17 (8.62%)∗13 (6.59%)∗Excessive increase group5842 (72.41%)16 (27.58%)6 (10.34%)16 (27.58%)9 (15.51%)χ26.5223.8474.1626.9883.154P0.0040.0120.0170.0020.024Compared with the excessive increase group,∗P < 0.05.


## 3.4. Comparison of the Prepregnancy BMI and Neonatal Conditions

The incidences of huge infants, premature delivery, and neonatal asphyxia in the overweight/obese group were significantly higher than those in the normal group (P<0.05), and incidences in the obese group were higher than those in the overweight group. The overweight and obese group normal neonatal weight cases were lower than the normal group (P<0.05), and normal neonatal weight cases in the obese group were lower than those in the overweight group (P<0.05, Table 4).Table 4
Comparison of the prepregnancy BMI and neonatal conditions (n, %).
GroupCaseLow neonatal weightNormal neonatal weightHuge infantsPremature deliveryNeonatal asphyxiaNormal group2434 (1.64%)231 (95.07%)8 (3.29%)22 (9.05%)20 (8.23%)Overweight group761 (1.31%)66 (86.85%)∗9 (11.84%)∗13 (17.10%)∗12 (15.78%)∗Obese group391 (2.56%)30 (76.93%)∗#8 (20.51%)∗#8 (20.51%)∗#11 (28.20%)∗#χ21.7922.5478.6625.9783.459P0.0760.0370.0010.0030.029Compared with the normal group,∗P < 0.05; compared with the overweight group, P#<0.05.


## 3.5. Comparison of the BMI Increase and Neonatal Conditions

The incidences of huge infants and neonatal asphyxia in the excessive increase group were significantly higher than those in the appropriate and deficient increase groups, and normal neonatal weight cases in the excessive increase group were lower than those in the other groups (P<0.05). The incidences of low neonatal weight and premature delivery were higher in the excessive increase and deficient increase group in comparison with the appropriate increase group (P<0.05, Table 5).Table 5
Comparison of the BMI increase and neonatal conditions (n, %).
GroupCaseLow neonatal weightNormal neonatal weightHuge infantsPremature deliveryNeonatal asphyxiaDeficient increase group1034 (3.88%)∗94 (91.27%)#5 (4.85%)#18 (17.47%)∗13 (12.62%)#Appropriate increase group1970186 (94.42%)#11 (5.58%)#16 (8.12%)18 (9.13%)#Excessive increase group582 (3.44%)∗47 (81.04%)9 (15.51%)9 (15.51%)∗12 (20.68%)χ24.9224.5479.6725.4765.884P0.0230.0270.0010.0150.013Compared with the appropriate increase group,∗P < 0.05; compared with the excessive increase group, P#<0.05.


## 4. Discussion

The nutrition reserved by pregnant women before pregnancy and the nutrition absorbed during pregnancy are the basis for the growth and development of the fetus. Clinically, the weight of the pregnant woman during pregnancy is often used to indirectly evaluate the growth and development of the fetus and the weight of the newborn; therefore, the weight of pregnant women is a necessary item for pregnancy examination [11]. Obesity is a risk factor for a variety of cardiovascular and endocrine diseases. At present, BMI is applied to express the degree of obesity in health and medical communities due to the comprehensive consideration of height and weight [12]. In recent years, the proportion of obese pregnant women has risen sharply, which greatly increases the incidence of HDP and GDM and causes great harm to the health of the puerpera and newborn [13, 14]. Also, high BMI during pregnancy would cause fat accumulated in the pelvic cavity of pregnant women, then result in the reduction of the pelvic space and the block of the fetal head in descent, prolong the labour process, and even influence the delivery outcome [15–17]. Moreover, adipose tissue secretes a large number of cytokines, which could lead to hormone secretion disorder, uterine atony during delivery, prolonged labour process, and risk of postpartum hemorrhage [18–20]. The results of the study showed that the incidences of cesarean section, postpartum hemorrhage, GDM, and HDP in overweight, obesity, and excessive increase groups were significantly higher than those in the normal group and appropriate/insufficient increase group, and the rate of natural labour in the obese group and excessive increase group was lower than that in the normal group, overweight group, and appropriate/deficient increase group. The results showed that high BMI before pregnancy and excessive weight gain during pregnancy increased the risk of HDP, GDM, postpartum hemorrhage, and cesarean section.Excessive glucose in GDM pregnant women will stimulate the fetal pancreas to secrete a large amount of insulin through the placenta. Moreover, the fetal insulin level in late pregnancy is closely related to the incidence of macrosomia, and macrosomia will increase the risk of cesarean section and dystocia [21, 22]. The neonatal asphyxia rate and mortality of preterm infants are higher than those of normal gestational age infants. The prognosis of preterm infants is the focus of clinical attention, but the etiology of preterm birth is still not completely clear [23, 24]. The development of the fetus is closely related to the nutrition which is taken by pregnant women during pregnancy. Therefore, deficient increase in BMI and lack of nutrition would cause the incidence of premature delivery and low neonatal weight increased [25–27]. In addition, an excessive increase of BMI during pregnancy leads to an increase in the incidence of GDM and HDP, which results in therapeutic preterm birth and insufficient blood supply to the placenta from HDP. Therefore, fetal development will be affected, and the incidence of low birth weight will be increased [28, 29]. Besides, obese pregnant women with prolonged labour may increase the incidence of neonatal asphyxia [30–32]. The results of this study showed that the incidence of macrosomia and neonatal asphyxia in overweight, obese, and excessive increase groups was higher than that in normal, appropriate increase, and deficient increase groups. The incidence of premature delivery in overweight and obese groups was higher than that in the normal group, and the incidence of low neonatal weight and premature delivery in the excessive increase group and deficient increase group was higher than that in the appropriate increase group. The results indicated that high BMI before pregnancy and excessive weight gain during pregnancy increased the incidence of huge infants and neonatal asphyxia. Besides, excessive and deficient weight gain during pregnancy could increase the incidence of premature and low-weight infants.In conclusion, high BMI before pregnancy and excessive weight gain during pregnancy can lead to abnormal neonatal weight and increase the incidence of adverse delivery outcomes. Therefore, in order to reduce the incidence of abnormal neonatal weight and adverse delivery outcomes and avoid the adverse effects of pregnancy and postpartum, medical staff should guide obese women who plan to get pregnant to control their weight by reasonable diet and appropriate exercise.



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