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Obesity, pregnancy and delivery

Obesity represents a significant medical problem in modern world, especially in developed and developing countries. Due to its destructive impact on health, great efforts are being made in order to reduce the number of obese people. Approximately 25% of women in their reproductive age are overweight. These women are obese when they enter pregnancy, which increases the risk of giving birth to a macrosomic newborn. On the other hand, the risk for a person to become obese adult increases if that person was born with increased birth weight. Obesity is defined as excess of adipose tissue which occurs due to imbalance between energy input and consumption, leading to multiple adverse pathophysiological mechanisms which endanger health. In 95% of cases, the etiology of obesity is unknown, but most people become obese simply due to eating habits. After a person becomes obese, all the other factors (reduced physical activity, changes in metabolic and hormonal mechanisms) are more and more expressed and are contributing to preservation and advancement of obesity. Due to alterations in target-organ sensitivity to insulin and pancreas’ ability to respond to increased need for insulin, obese people are more often affected by diabetes. Obese people have elevated triglycerides and cholesterol blood levels which, along with hypertension, leads to atherosclerosis. Due to hyperestrogenism, obese women are more often affected by breast and endometrial cancer and also by oligomenorrhea, amenorrhea and anovulatory cycles. In extremely obese people, upper-airway obstruction during sleep causes hypoxia and hypercapnia, which can lead to development of policytemia, pulmonary hypertension and chronic pulmonary heart. The body weight of obese people is 20-30% above average for a given height, age and sex. Different laboratory techniques have been used for estimating obesity and amount of adipose tissue, but due to their complexity they are not used in routine practice. Nowadays, mostly criteria based on height and weight are being used for estimating obesity. Index known as Body Mass Index (BMI) is generally accepted. It is calculated using formula W/H, where W stands for body weight in kilograms and H stands for height in meters. Based on BMI, women are grouped in 4 categories: 1. Thin = BMI < 19.9 kg/m², 2. Normal = BMI 20.0-24.9 kg/m², 3. Obese = BMI 25.0-29.9 kg/m², 4. Very obese = BMI > 30.0 kg/m². This classification was used in our study. Main advantage of BMI index is its simple calculation, but its limitation is absence of differentiation between obesity and increased muscle mass as the cause of increased body weight. BMI is well correlated with mortality – people with BMI in range 20 to 25 kg/m² have low risk, and those people with BMI higher than 30kg/m² have high risk of premature death. Women can enter pregnancy already overweight or they can experience significant increase in body weight, resulting in obesity. Those pregnancies are more often characterized by antepartal, intrapartal and postpartal complications. Among antepartal complications, authors describe hypertension, preeclampsia, gestational diabetes and urinary infections ; among intrapartal complications - umbilical cord complications, meconium stained amniotic fluid and prolonged second phase of delivery ; and among pospartal complications – hemorrhage and puerperal infections. All authors agree that women which have high body weight prior to delivery, more frequently give birth to macrosomic newborns, which increases the use of oxytocin and the need for cesarean sections. There is higher occurrence of perinatal mortality in obese pregnant women, related to premature deliveries and twin-pregnancies which lead to increased number of premature deliveries. On the other hand, high increase in body weight of pregnant women who had high BMI before pregnancy, can lead to more frequent deliveries of newborns with low birth weight. Newborns born by obese mothers have higher risk for congenital malformations. Newborns of extremely obese pregnant women (BMI>31kg/m²) more often manifest neural tube defects along with other anomalies of central nervous system, anomalies of the great vessels and frontal abdominal wall defects. Pregnant women that had high increase in body weight during pregnancy usually enter next pregnancy with increased body weight.

obesity; pregnancy; delivery

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