the prevalence of obesity has increased dramatically in recent decades both in the united states and abroad .
today , it is estimated that as many as 34% of women of reproductive age are obese ( bmi  30  kg / m ) .
studies have consistently shown a significant association between obesity and adverse pregnancy outcomes [ 24 ] .
specifically , obesity increases the risk of miscarriage , gestational diabetes , hypertensive complications , infections , postterm pregnancy , and cesarean section delivery [ 59 ] .
additionally , obesity is associated with numerous fetal risks including congenital anomalies , macrosomia , and perinatal morbidity and mortality [ 6 , 7 , 1012 ] .
however , it remains unclear whether obesity by itself , independent of diabetes and hypertension , is a predictor of adverse pregnancy outcome .
a number of studies have provided indirect data suggesting a possible causal association between maternal adiposity and pregnancy complications .
endocrine abnormalities associated with obesity , that is , increased levels of insulin , androgens , and leptin , have been incriminated [ 1316 ] .
in fact , adipose tissue appears to be an active endocrine organ that secretes several proinflammatory cytokines , which may result in endothelial dysfunction in the mother and placenta and ultimately lead to adverse pregnancy outcome [ 1316 ] .
have demonstrated that obesity in pregnancy results in an exaggerated inflammatory response in the placenta with accumulation of multiple subsets of macrophages and production of proinflammatory mediators .
we hypothesize that the inflammatory and altered endocrine milieu in which the fetus develops may have detrimental consequences on fetal well - being . in this study
, we investigate the impact of obesity on fetal well - being , as assessed by fetal blood gas parameters ( bgps ) , in a retrospective cohort of glucose - tolerant and nonhypertensive women . to the best of our knowledge ,
this is the first systematic assessment of the impact of obesity per se on umbilical artery bgp .
we searched our prospectively maintained database for all patients admitted to the labor and delivery department in our institution between january , 2011 and july , 2011 .
patients with comorbidities ( diabetes or hypertension ) or conditions that could influence fetal bgp were systematically excluded from the analysis .
exclusion criteria were as follows : hypertension or pregnancy - induced hypertension ; preeclampsia ; diabetes , gestational diabetes or impaired glucose tolerance ; active smoking or drug use ; any medical comorbidity including congestive heart failure , chronic kidney disease , or chronic respiratory disease ; placental abruption ; chorioamniointis ; nonreassuring fetal heart rate patterns ; emergency cesarean section delivery ; vacuum extraction delivery ; shoulder dystocia ; multiple pregnancy ; preterm birth ; and congenital abnormality . because the study was designed to compare obese to normal weight patients with regard to bgp , overweight patients ( bmi 2529.9  kg / m ) were excluded from the analysis .
medical charts and laboratory results were carefully reviewed to determine patient 's age , race , bmi , gravity , parity , number of prenatal visits , gestational age at delivery , mode of delivery , number of previous cesarean section deliveries , group b streptococcal colonization , umbilical artery ph , po2 , pco2 and base deficit , and apgar score at 1 and 5 minutes .
patients were divided into 2 groups based on their prepregnancy bmi as follows : normal weight ( < 25 
kg / m , n = 50 ) and obese ( 30  kg / m , n = 50 ) .
gbs colonization was marked as positive if any of the vaginal , anal , or urine cultures were positive at anytime .  
a comparative analysis of bgp between the normal weight group and the obese group was conducted .
data are presented as mean and standard deviation for continuous variables and as frequency for categorical variables .
statistical analysis of categorical variables was carried out using chi - square and fisher 's exact tests as appropriate .
this study would have 99% power to detect a mean difference of 10 in base excess ( type i error 5% ) and 70% power to detect a mean difference of 5 ( type i error 5% ) .
all statistical analyses including sample size calculation were performed usingspss(ibm corporation , armonk , ny , usa ) .
a total of 100 patients ( 50 lean and 50 obese ) were included in the study .
bmi was 20.9  2.1  kg / m on average in the normal weight group and 35.7  5.0  kg / m in the obese group .
there were no significant differences between the 2 groups with respect to all baseline characteristics except for parity ( table 1 ) .
mean age was 25  6.9 years in the normal weight group versus 26.9  6.6 years in the obese group ( p = 0.25 ) .
hispanic patients accounted for 70% ( n = 35 ) of the normal weight group versus 66% ( n = 33 ) of the obese group ( p = 0.67 ) .
a cesarean section was performed in 22% ( n = 11 ) of normal bmi patients compared to 28% ( n = 14 ) of obese patients ( p = 0.49 ) .
eight ( 16% ) lean patients and 9 ( 18% ) obese patients tested positive for gbs ( p = 0.79 ) .  
there were no significant differences in any of the umbilical artery bgp between the two groups .
ph and pco2 were , respectively , 7.26  0.06 and 54.61  10.3  mmhg on average in the normal weight group versus 7.26  0.08 ( p = 0.95 ) and 55.12  13.9  mmhg ( p = 0.83 ) in the obese group .
mean umbilical artery po2 was 25.7  9.8  mmhg in lean patients versus 23.7  8.9  mmhg in obese patients ( p = 0.48 ) .
newborns of lean patients had a 3.74    1.8  mmol / l base deficit on average compared with 3.77  2.4  mmol / l for newborns of obese patients ( p = 0.79 ) .
mean apgar scores at 1 and 5 minutes were , respectively , 8.78  0.5 and 9.08  0.4 for newborns of lean patients versus 8.72  0.6 ( p = 0.62 ) and 9.14    0.4 ( p = 0.46 ) for newborns of obese patients .
similarly , pearson 's correlation coefficient did not reveal any significant correlation between bmi and bgp or apgar scores ( table 2 ) .
  it is thought that obesity increases the risk of maternal and fetal complications mainly through its association with diabetes , hypertension , and other comorbid conditions .
thus , we excluded these potentially confounding factors from the analysis and investigated the impact of obesity per se on fetal well - being , namely , umbilical artery bgp and apgar scores . furthermore , because overweight is regarded as an intermediate state between normal weight and obesity , such patients were excluded from the analysis . despite a well - matched study population for baseline characteristics , we did not find any significant difference between obese and lean patients with respect to bgp or apgar scores .
our results suggest that obesity may not affect fetal well - being in patients with no comorbidities such as gestational diabetes or hypertension .
only a few studies have investigated the association between obesity per se and pregnancy outcome . in a recent large study ,
owens and colleagues   examined the impact of obesity on pregnancy outcome in 2329 glucose - tolerant women .
they found an increased incidence of cesarean deliveries , hypertensive complications , miscarriages , macrosomia , shoulder dystocia , and congenital malformations in obese women as compared to normal weight women .
however , the authors did not assess the impact of bmi on umbilical artery bgp .
moreover , patients with hypertension or gestational hypertension were not excluded from the analysis which could have introduced bias into the study , especially given the established association between obesity and hypertension - related pregnancy complications . in another large study ,
jensen and colleagues   assessed the relationship between prepregnancy bmi and pregnancy outcome in 2459 glucose - tolerant danish women .
the risk of cesarean section , induction of labor , hypertensive complications , and macrosomia was significantly increased in obese women compared with normal weight women .
more importantly , however , the frequencies of shoulder dystocia , preterm delivery , and infant morbidity other than macrosomia were not significantly associated with maternal bmi .
these findings are in line with the results of our study and suggest that obesity may not increase infant morbidity in the absence of diabetes or other comorbidities . the effect of obesity on umbilical artery bgp ( among other variables )
the authors reported no difference between obese and lean patients with regard to umbilical ph or apgar scores .
although the results of this study are in line with our findings , patients with diabetes / impaired glucose tolerance or hypertension were not excluded from the analysis which precludes any confident conclusion as to the impact of obesity , as an independent factor , on bgp and apgar scores .
the limitations of this study stem primarily from its retrospective design , small sample size , and the absence of randomization .
although patients with nonreassuring fetal heart rate patterns ( category iii tracing ) and vacuum extraction delivery were excluded , the influence of labor on the acid base status of the newborn may not have been completely controlled for in this study .
we found no relation between maternal bmi per se and umbilical artery bgp in a retrospective cohort of 100 patients .
thus , obese women who are glucose - tolerant and nonhypertensive may not be at increased risk of perinatal morbidity .
larger prospective studies are needed to confirm the absence of association between obesity and fetal well - being parameters .
 this study was undertaken to assess the impact of obesity on fetal well - being in glucose - tolerant and nonhypertensive women . 
 medical charts of all patients admitted to the labor and delivery department at our institution between january , 2011 and july , 2011 were retrospectively reviewed . 
 patients with diabetes / impaired glucose tolerance or hypertension were excluded . 
 a total of 100 women , 50 lean and 50 obese , were included . 
 umbilical artery blood gas parameters ( bgps ) were compared in lean ( < 25  kg / m2 ) and obese ( 30  kg / m2 ) women . 
 obese and lean women were comparable with respect to all baseline characteristics . 
 there was no difference in any of the bgp or apgar scores between obese and lean patients . 
 pearson 's correlation coefficient found no significant correlation between bmi and bgp / apgar scores . 
 maternal obesity does not seem to affect bgp and fetal well - being in glucose - tolerant and nonhypertensive women . 
1. Introduction
2. Material and Methods
3. Results 
4. Discussion
5. Conclusion