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

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


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


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 38th and 41st 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.


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).