Kirchengast S; Hartmann B

Special Article - Obesity in Pregnancy

Ann Obes Disord. 2017; 2(1): 1017.

Maternal Obesity Increases the Risk of Primary as Well as Secondary Caesarean Section

Kirchengast S¹* and Hartmann B²

¹Department Anthropology, University of Vienna, Austria

²Department of Gynecology and Obstetrics, Hospital of Neunkirchen, Austria

*Corresponding author: Kirchengast Sylvia, Department of Anthropology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria

Received: November 28, 2016; Accepted: January 09, 2017; Published: January 11, 2017

Abstract

Maternal obesity is not only associated with pregnancy outcome but also with the mode of delivery. In the present study the impact of maternal prepregnancy weight status on the mode of delivery, in particular on caesarean section rate was tested. The data of 3451 live births taking place at the Viennese University Hospital were analyzed. Maternal somatometrics (height, weight, weight gain) and newborn somatic characteristics (birth weight, birth length, head dimensions, APGAR scores) were documented. Prepregnancy weight status was classified using Body Mass Index (BMI) categories published by the WHO. The caesarean section rate was 15.6%. (6.8% primary CS, 8.8% secondary CS). 24.2% of the mothers were overweight, 9.6% obese and 0.8% morbidly obese before pregnancy. Maternal prepregnancy BMI was significantly associated with newborn size. The relative risk to give birth to a macrosome newborn was significantly increased among overweight (OR 1.46 CI 1.24- 1.72), obese (OR 1.76 CI 1.40-2.19) and morbidly obese mothers (OR 1.51 CI 0.57-3.99). The relative risk of caesarean section increased significantly with increasing prepregnancy weight status (p<0.04). Morbidly obese women showed the significantly highest rate of caesarean section (33.4%; primary CS 16.7%, secondary CS 16.7%). The relative risk of experiencing caesarean section was significantly higher among morbidly obese women than among underweight (OR 3.57 CI 1.85-6.86), normal weight (OR 2.89 CI 1.25-6.69), overweight (OR 2.27 CI 0.99-5-22) and even obese women (OR 2.11 CI 0.94- 4.72). Prepregnancy obesity is clearly a significant risk factor of newborn macrosomia and primary as well as secondary caesarean section.

Keywords: Pre-pregnancy obesity; Newborn size; Mode of delivery; Caesarean section

Introduction

The prevalence of overweight and obesity as a worldwide epidemic has increased dramatically since the beginning of the 21rst century [1-3]. In 2008 for the first time in the long history of Homo sapiens, the number of obese people on earth exceeded the number of people who suffer from starvation and malnutrition [4]. Currently more than 1.9 billion adults, 18 years and older, were overweight. Of these over 600 million correspond to the definition of obesity [5]. From the viewpoint of public health this high prevalence of overweight and obesity is a major concern because overweight and especially obesity increase rates of metabolic diseases such as diabetes type II, cardiovascular diseases such as heart disease, stroke, hypertension, but also pancreatitis, osteoarthritis and cancer [6]. Obesity however, is also related to reproductive problems, such as increased infertility rates in women as well as in men [7,8]. A special problem represents obesity among women of reproductive age. In the United States more than 50% of women ageing between 20 and 39 years are overweight or obese [6,9,10]. Europe seems to follow a similar pattern, albeit with some delay. Currently one in five pregnant women can be classified as obese in Europe [5,11]. This high rate of obesity among women of childbearing age represents an enormous public health problem because obesity during pregnancy has been associated with both short- and long-term health effects for women and their offspring [9,12-16]. In general, maternal obesity before and during pregnancy increases the risk for morbidity and mortality of mother and child. Furthermore maternal obesity is associated with an increased risk of miscarriage [17,18], hypertensive disorders such as pre-eclampsia, hypertension and thromboembolic complications [11,19] but also and increased risk of Gestational Diabetes (GDM) and pre-eclampsia [20,21]. On the other hand maternal obesity bears also technical problems: ultrasonography in morbidly obese patients can be challenging because fat tissue attenuates the ultrasound signal by absorption of associated energy [19]. Obesity related problems occur also during parturition. Obese women are more likely to face induction of labor, caesarean section, anesthetic problems, wound infections and postpartum hemorrhage [11,22-24]. Especially caesarean section rates are extremely high among obese women. Several studies have shown an excess risk of caesarean section among overweight, obese and morbidly obese women [25-31]. Caesarean delivery risk is increased by 50% in overweight women and is more than double for obese women in comparison to normal weight women [32]. Consequently prepregnancy obesity is mentioned as a major risk factor for caesarean sections. The aim of the present study was to analyze the impact of maternal prepregnancy weight status, gestational weight, body height but also newborn somatometrics on the mode of delivery.

Materials and Methods

Data set

This retrospective study is based on a data set of 3451 singleton births which took place at the University Clinic of Gynecology and Obstetrics in Vienna, Austria between 1995 and 2000 Although a total of 7138 births were collected, only 3451 met the strict inclusion and exclusion criteria. The present analyses included exclusively births which took place between the 38^th and 41^st gestational week, because term birth of comparable gestational length was a strict inclusion criterion Furthermore exclusively nulliparous women ageing between 19 and 42 years whose first prenatal check took place during the eighth week of gestation were enrolled in the present study. Additionally the following inclusion criteria were used: all prenatal check-ups of the Austrian mother-child passport completed, the delivery of a single infant without congenital malformations, no registered maternal diseases before and during pregnancy, no hypertension (BP< 150/90 mmHg), no proteinuria, no glucosuria, no pregnancy related immunization. On the other hand caesarean delivery on maternal request, coincident medical diseases such as gestational diabetes or preeclampsia, drug or alcohol abuse, twin birth or IVF were strict exclusion criteria. Therefore only 3451 births were considered for final analyses. Gestational age was calculated in terms of the number of weeks from the beginning of the last menstrual bleeding to the date of delivery (=duration of amenorrhoea). All subjects originated from Austrian or central Europe.

Maternal parameters

All women enrolled in the present study aged between 19 and 42 years (x=28.5 ±4.4). Furthermore the following maternal somatometric parameters were determined at the first prenatal visit: Stature height was measured to the nearest 0.5cm. Body weight was measured to the nearest 0.1kg on a balance beam scale. Additionally maternal weight at the End of Pregnancy (EPW) was measured before birth. The weight gain during pregnancy (PWG) was calculated by subtraction of pre-pregnancy weight from body weight at the end of pregnancy. A gestational weight gain below 7kg was classified as low gestational weight gain, while a gestational weight gain above 15kg was defined as high gestational weight gain.

Maternal pre-pregnancy weight status was determined by the body mass index (BMI) kg/m² using stature height and pre-pregnancy weight. To classify maternal weight status the cut-offs published by the WHO [33] were used.

Underweight = BMI < 18.50kg/m²

Normal weight = BMI 18.50 to 24.99 kg/m²

Overweight = BMI 25.00 to 29.99 kg/m²

Obesity = BMI 30.00 to 39.99 kg/m²

Morbid Obesity = BMI > 40,00kg/m²

Newborn parameters

Birth weight, birth length and head circumference were taken directly from newborn immediately after birth. Newborn weight status was defined as follows: very low < 1500g, low 1500-2500 g, normal 2500-400 g and high (macrosomia) >4000g. Furthermore the one- and the five minute APGAR scores for the evaluation of the newborn were determined.

Obstetrical characteristics

Four categories of birth mode were distinguished:

Spontaneous vaginal birth

Assisted vaginal birth i.e. vacuum extraction or forceps

Primary caesarean section

Secondary caesarean section

Caesarean sections requested by the mother without any medical indication were not carried out at this hospital.

Statistical analyses

Statistical analyses were performed by means of SPSS for Windows program Version 22.0. After calculating descriptive statistics (means, SDs), group differences were tested regarding their statistical significance using Duncan analyze and Student t-tests.

Furthermore χ² analyses and odds ratios were computed. Multiple regression analyses were performed to test the impact of maternal prepregnancy BMI, stature height, gestational weight gain, birth weight, birth length and newborn head circumference on the mode of delivery. Additionally binary logistic regressions were computed in order to test the association of maternal stature, prepregnancy body mass index as well as newborn anthropometrics and caesarean section. Vaginal delivery was coded as 1; a caesarean section was coded as 2.

Results

Mode of delivery

The majority of women (74.3%) experienced a spontaneous vaginal birth. 10.2% of the women needed forceps or vacuum extraction. Primary caesarean section was performed among 6.8% of the women, while 8.8% experienced a secondary or emergency caesarean section.

Maternal and newborn anthropometrics

Maternal and newborn anthropometrics characteristics are presented in Table 1. As to be seen, only less than 3% of the women corresponded to the definitions of underweight (BMI < 18.5kg/m²), 62.5% of the women corresponded to the definitions of normal weight (BMI 18.5-24.99 kg/m²). 24.2% of the women were overweight during prepregnancy phase, whereas obesity during prepregnancy phase was found among 9.6%. 0.8% of the women were classified as morbidly obese i.e. the BMI was higher than 40.00kg/m². 55% of the women experienced a weight gain between 7 and 15kg, 14.5% experienced a weight gain of less than 7kg and 30.5% experienced a weight gain higher than 15kg. Since only term births were included in the present analyses, none of the newborns was lighter than 1500g and only 1.5% of the newborn were lighter than 2500g. The majority of newborns (82.3%) corresponded to the definitions of normal weight (2500- 4000g), 17.2% newborns however were classified as macrosome (>4000g). Macrosomia was significantly more often found among overweight and obese mothers compared to normal weight or underweight women (Figure 1). In comparison to normal weight mothers the relative risk to give birth to a macrosome newborn was significantly (p< 0.001) increased among overweight (OR 1.46 CI 1.24-1.72), obese (OR 1.76 CI 1.40-2.19) as well as morbidly obese mothers (OR 1.51 CI 0.57-3.99).

Table 1: Sample description Maternal and newborn characteristics, (descriptive statistics mean, sd, range, absolute and relative frequencies).




  
    Maternal parameters 
    x (SD) 
    range 
    n(%) 
  
  
    Maternal age (yrs)
    28.5 (4.4)
    19-42
    
  
  
    Stature height (cm)
    168.4 (6.5)
    144-193
    
  
  
    Prepregnancy weight    (kg)
    68.9 (13.1)
    37 -142
    
  
  
    End of pregnancy    weight (kg)
    81.2 (13.3)
    48-146
    
  
  
    Gestational weight    gain (kg)
    12.3 (4.8)
    2.0 -29.0
    
  
  
    Gestational weight    gain < 7kg
    
    
    500 (14.5%)
  
  
    Gestational weight    gain 7-15kg
    
    
    1898 (55.0%)
  
  
    Gestational weight    gain >15kg
    
    
    1053 (30.5%)
  
  
    Prepregnancy body    mass index (kg/m²)
    24.82 (4.29)
    15.1-50.3
    
  
  
    Prepregnancy weight    status
    
    
    
  
  
    underweight BMI    < 18.50
    
    
    98 (2.8%)
  
  
    normal weight BMI    18.50-24.99
    
    
    2158 (62.5%)
  
  
    overweight BMI    25.00-29.99
    
    
    836 (24.2%)
  
  
    obese BMI    30.00-39.99
    
    
    333 (9.6%)
  
  
    Morbidly obese BMI    >40.00
    
    
    26 (0.8%)
  
  
    Newborn parameters 
    
    
    
  
  
    Sex
    
    
    
  
  
    female
    
    
    1733 (50.2%)
  
  
    male
    
    
    1718 (49.8%)
  
  
    Birth weight (g)
    3451.7 (484.8)
    1650-5110
    
  
  
    Birth length (cm)
    50.9 (2.5)
    32-59
    
  
  
    Head circumference    (cm)
    35.2 (1.4)
    29-39
    
  
  
    Newborn weight    status
    
    
    
  
  
    very low birth    weight < 1500g
    
    
    0 (0.0%)
  
  
    low birth weight    1500-2499g
    
    
    50 (1.4%)
  
  
    normal birth weight    2500-4000g
    
    
    2807 (81.3%)
  
  
    macrosome >4000g
    
    
    594 (17.2%)
  
  
    Apgar 1
    8.7 (0.9)
    0-10
    
  
  
    Apgar 5
    9.7 (0.8)
    10-Jan



Table 1:  Sample description Maternal and newborn characteristics, (descriptive
statistics mean, sd, range, absolute and relative frequencies).

Figure 1: Pre-pregnancy weight status and prevalence of macrosomia (p <0.01).

    
    
    Figure 1: Pre-pregnancy weight status and prevalence of macrosomia (p <0.01).

Maternal and newborn characteristics according to the mode of delivery

Comparing vaginal delivery (spontaneous + VE + forceps) and caesarean section (primary CS + secondary CS) it turned out that women experiencing caesarean section were significantly older, shorter but heavier before and at the end of pregnancy. Furthermore the caesarean section group experienced a significantly higher gestational weight gain and exhibited a significantly higher prepregnancy body mass index. Newborns of the caesarean section group were significantly lighter and shorter. Furthermore their Apgar scores one and five minutes after birth were significantly lower than that among newborns that experienced a vaginal delivery (Table 2). Comparing all four modes of delivery it could be shown that women experiencing secondary caesarean section were significantly shorter than women experiencing primary caesarean section or vaginal delivery. In contrast, women experiencing primary or secondary caesarean section exhibited a significantly higher prepregnancy body mass index than women who experienced vaginal deliveries. The significantly highest gestational weight gain was found among the secondary caesarean section group (Table 3).

Table 2: Differences in maternal and newborn characteristics according to te mode of delivery. Vaginal delivery (VD) vs caesarean section (CS). (Student t-tests).




  
     
    VD 
      (n=2914)
    CS 
      (n=536)
    Sig. 
  
  
    x (SD)
    x (SD)
    p-value
  
  
    Maternal age (yrs)
    28.4 (4.4)
    28.8 (4.3)
    0.047
  
  
    Maternal stature    height (cm)
    168.6 (6.4)
    166.9 (7.0)
    0.001
  
  
    Prepregnancy weight    (kg)
    68.9 (12.9)
    69.1 (13.4)
    0.643
  
  
    End of pregnancy    weight
    80.9 (13.2)
    82.6 (13.5)
    0.011
  
  
    Gestational weight    gain (kg)
    12.1 (4.7)
    13.4 (4.8)
    0.001
  
  
    Prepregnancy weight    status (BMI) (kg/m²)
    24.19 (4.23)
    24.81 (4.63)
    0.003
  
  
    Birth weight (g)
    3566.3 (468.2)
    3472.2 (560.7)
    0.001
  
  
    Birth length (cm)
    53.0 (2.5)
    52.4 (2.8)
    0.001
  
  
    Head circumference    (cm)
    35.3 (1.4)
    35.4 (1.6)
    0.058
  
  
    Apgar 1min
    8.7 (0.9)
    8.6 (1.0)
    0.001
  
  
    Apgar 5min.
    9,7 (0.7)
    9.6 (0.8)
    0.016
  
  
    VD: Vaginal    Delivery; CS: Caesarean Section.



Table 2:  Differences in maternal and newborn characteristics according to te
mode of delivery. Vaginal delivery (VD) vs caesarean section (CS). (Student
t-tests).

Table 3: Maternal and newborn characteristic according to mode of delivery Duncan analyses.




  
    
    Mode of delivery 
    
  
  
    Spontaneous vaginal
    Forceps + VE
    Primary CS
    Secondary CS
    Sig.
  
  
    Maternal parameters 
    x
    (SD)
    x
    SD
    x
    SD
    x
    SD
    p-value
  
  
    Age (yrs)
    28.5
    (4.4)^c
    28
    (4.3)^c
    29.3
    (4.3)^a,b,d
    28.4
    (4.3)^c
    0.01
  
  
    Body height (cm)
    168.6
    (6.4)^c,d
    168.3
    (6.2)^d
    167.5
    (7.2)^a,d
    166.6
    (6.8)^a,b,c
    0.001
  
  
    Prepregnancy weight    (kg)
    68.9
    (13)
    68.1
    (12.6)
    69.7
    (13.5)
    68.7
    (13.2)
    0.524
  
  
    End of pregnancy    weight (kg)
    80.9
    (13.2)
    81.2
    (13.4)
    82.2
    (13.3)
    82.8
    (13.7)
    0.075
  
  
    Pregnancy weight    gain (kg)
    11.9
    (4.7)^b,d
    13.1
    (4.9)^a,d
    12.6
    (4.5)^d
    14.1
    (4.9)^a,b,c
    0.000
  
  
    Prepregnancy BMI    (kg/m²)
    24.22
    (4.24)^c,d
    24.02
    (4.14)^c,d
    24.86
    (4.86)^a,b
    24.76
    (4.45)^a,b
    0.022
  
  
    Newborn parameters 
    
    
    
    
    
    
    
    
    
  
  
    Birth weight (g)
    3569.2
    (467.9)^c
    3545.1
    (470.5)^c
    3387.7
    (522.9)^a,b,d
    3537.2
    (580.7)^c
    0.001
  
  
    Birth length (cm)
    52.9
    (2.5)^c
    53.2
    (2.6)^c
    51.9
    (2.7)^a,b,d
    52.8
    (2.8)^c
    0.001
  
  
    Head circumference    (cm)
    35.3
    (1.3)^b,c
    35.5
    (1.5)^a,d
    35.5
    (1.6)^a,d
    35.4
    (1.6)^b,c
    0.001
  
  
    Apgar 1min
    8.8
    (0.8)^b,d
    8.3
    (0.9)^a,c
    8.8
    (0.7)^b,d
    8.4
    (1.1)^a,c
    0.001
  
  
    Apgar 5min
    9.7
    (0.8)^b,d
    9.4
    (0.9)^a,c
    9.7
    (0.7)^b,d
    9.5
    (0.9)^a,c
    0.001
  
  
    VE: Vacuum    Extraction; CS: Caesarean Section;
      a: significantly    different from spontaneous vaginal birth;
      b: significantly    different from forceps + vacuum extraction;
      c: significantly    different from primary caesarean section;
      d: significantly    different from secondary caesarean section.



Table 3:  Maternal and newborn characteristic according to mode of delivery Duncan analyses.

Concerning newborn characteristics it turned out, that newborns who were delivered by primary caesarean section were significantly lighter and shorter than all other newborns. On the other hand the significantly largest head circumference was found among newborns delivered by primary caesarean section as well as vacuum extraction and forceps. The Apgar scores one and five minutes after delivery were significantly lowest among newborns delivered by forceps and vacuum extraction followed by newborns experiencing secondary caesarean section.

Prepregnancy weight status and mode of delivery

As to be seen in Figure 2, caesarean section rate increased significantly with increasing maternal prepregnancy weight status. This was true of primary as well as secondary caesarean sections. Morbidly obese women (BMI > 40.00kg/m²) showed the significantly highest rate of caesarean sections while the lowest percentage of caesarean sections was found among underweight women (χ² = 21.04; p< 0.04). With increasing maternal prepregnancy weight status the relative risk of a caesarean section increased significantly. An especially high risk of caesarean section was found among morbidly obese women (BMI > 40.00kg/m²), in comparison to underweight (OR 3.57; CI 1.85-6.86) and normal weight women (OR 2.89; CI 1.25-6.69). The relative risk of experiencing a caesarean section among morbidly obese women was also significantly increased in comparison to overweight (OR 2.27; CI 0.99 - 5.22) and even obese women (OR 2.11; CI 0.94-4.72). The observed significant impact of maternal prepregnancy weight status on the mode of delivery was corroborated by the results of a binary logistic regression analyses as well as the multiple repression analysis. It could be shown that maternal prepregnancy body mass index had an independent positive effect on caesarean section rate. The risk of caesarean section increased significantly with increasing maternal age prepregnancy body mass index, gestational weight gain and newborn head circumference, but also with decreasing maternal body height and newborn weight (Tables 4 & 5).

Table 4: The impact of maternal and newborn somatometry on mode of delivery. Binary logistic regression analyses (spontaneous =1, section =2).




  
    Variable 
    Coefficient B 
    SE 
    Significance 
    95% CI 
  
  
    Maternal age
    0.03
    0.01
    0.002
    1.01-1.06
  
  
    Maternal height
    -0.03
    0.01
    0.001
    0.96-0.98
  
  
    Prepregancy BMI
    0.05
    0.01
    0.001
    1.03-1.08
  
  
    Gestational weight    gain
    0.08
    0.01
    0.001
    1.06-1.11
  
  
    Birth weight
    -0,01
    0.01
    0.001
    0.99-0.99
  
  
    Birth length
    -0.07
    0.03
    0.010
    0.88-0.98
  
  
    Head circumferences
    0.33
    0.05
    0.001
    1.26-1.53



Table 4:  The impact of maternal and newborn somatometry on mode of delivery.
Binary logistic regression analyses (spontaneous =1, section =2).

Table 5: The impact of maternal and newborn parameters on delivery mode. Linear regression analyses.




  
    
    R²
    Coefficient
    SE
    Sig.
    95% CI
  
  
    Dependent variable:    Mode of delivery 
  
  
    Maternal age
    0.2
    0.01
    0
    0.054
    0.01-0.02
  
  
    Maternal stature    height
    -0.01
    0
    0.001
    -0.02- -0.01
  
  
    Prepregnancy BMI
    0.02
    0
    0.001
    0.01-0.03
  
  
    Gestational weight    gain
    0.03
    0
    0.001
    0.03-0.04
  
  
    Birth weight
    0.01
    0
    0.001
    0.01-0.02
  
  
    Birth length
    -0.01
    0.01
    0.304
    -0.03-0.01
  
  
    Head circumference
    0.11
    0.02
    0.001
    0.08-0.15



Table 5:  The impact of maternal and newborn parameters on delivery mode.
Linear regression analyses.

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Citation: Kirchengast S and Hartmann B. Maternal Obesity Increases the Risk of Primary as Well as Secondary Caesarean Section. Ann Obes Disord. 2017; 2(1): 1017.

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