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Paper text:
diabetes mellitus ( dm ) is a chronic hyperglycemia caused by impaired insulin secretion . diabetes mellitus type i ( dm i ) has absolute insulin deficiency in contrast to diabetes mellitus type ii ( dm ii ) which has relative insulin deficiency .
gestational diabetes mellitus ( gdm ) is defined as impaired glucose tolerance with onset during pregnancy .
causal conditions are genetic predisposition , obesity , and lifestyle . during the second part of pregnancy , an increasing insulin resistance occurs due to changes in adipokinin , leptin , and tnf - alpha release .
the prevalence varies from 0.6% to 20% over the last 20 years . in germany , the prevalence in 2010 was about 3.7% with a distinct increase since 2002 .
there are various gdm complications for both mother and child : increasing numbers of maternal urinary tract infections and vaginal candida infections were observed .
there is an increase in risk for preterm birth   and pregnancy - induced hypertension ( pih ) .
fetal macrosomias , caesarean section , shoulder dystocia , birth injuries , and severe postpartum hemorrhage ( hapo ) occur more frequently in gdm patients .
various studies have shown that 3560% of patients with gdm develop dm ii or impaired glucose tolerance during the following 10 years [ 913 ] .
the fetus thus develops macrosomia or  as a result of acute and chronic oxygen deficiency  higher risks for growth restriction or even intrauterine fetal death .
macrosomia also increases shoulder dystocia rates , birth injuries , and increased caesarean section rates .
several studies showed a correlation between increased amniotic fluid insulin or c - peptide and gdm .
found increased levels of amniotic fluid c - peptide in patients who developed gdm , whereas carpenter and star provided evidence for increased amniotic fluid insulin in patients who later develop gdm . in contrast , in a prospective study our group could not demonstrate any correlation between amniotic fluid insulin , c - peptide , and the development of gdm .
all things considered , the role of increased amniotic fluid insulin and c - peptide and the development of a gdm remain to be elucidated .
therefore , in this study we investigated the correlation between amniotic fluid insulin , c - peptide , and fetal birth weight , as well as type of delivery and birth complications .
we included only women who underwent an amniocentesis between 14 and 22 weeks of gestation .
we included women who did not participate in gdm diagnostics to eliminate confounding effects of gdm therapy .
the data from these further unselected patients were collected before the general german gdm screening started in 2012 .
we retrospectively analyzed singleton pregnancy and delivery data of 144 women who underwent an amniocentesis at the wrzburg university hospital , department of obstetrics and gynecology .
we only included women with normal fetal chromosomal findings and normal amniotic fluid alpha fetoprotein ( afp ) who did not undergo testing for gdm and hence did not receive any therapy .
insulin was measured using an iod-125 radioimmunoassay kit ( schering , berlin , germany ) using the protocol for serum samples .
radioactively labeled insulin was used in a defined concentration , which competes with the sample of insulin to be measured .
the specific primary anti - insulin antibody binds less of the radioactively marked insulin the more sample insulin is bound . to clear the sample of free antigen , the antigen - antibody complexes were precipitated by a secondary antibody against the primary antibody . after the binding , reaction according to the manufacturer s instructions ,
the radioactive tracer insulin - i-125 and an anti - insulin mouse immunoglobulin were diluted with distilled water . for the generation of a standard curve ,
after 18 hours of incubation at room temperature , the insulin - ig complexes were precipitated .
the supernatant was discarded and radioactivity was measured with a gamma counter . using the standard curve , we calculated the insulin concentrations .
the lower detection limit was 4.2 u / ml the use of specific antibodies makes this assay precise ; it can distinguish small differences in concentration due to the sensitive detection of radioactivity .
c - peptide was measured using an immunoradiometric assay ( irma - c - pep kit ) .
this kit uses 2 monoclonal antibodies specific for different epitopes on the c - peptide antigen .
the capture antibody was coated on a well , whereas the signaling antibody with i-125 is soluble .
after incubation , we measured the radioactivity with a gamma counter and calculated the c - peptide concentrations according to the standard curve .
data concerning the pregnancies and births were noted and analyzed using spss 18.0.2 for windows and microsoft excel 2010 .
the mean newborn birth weight was 3420 g , whereas the subgroup of mature newborns showed a mean of 3530 g. the maternal age ranged from 19 to 44 years with a mean age of 35.6 years .
the total rate of vaginal deliveries was 81.9% ( of which 71.5% were spontaneous and 10.4% were operative ) , and the cesarean section rate was 18.1% .
the mean concentration was 4.364 u / ml , ranging from 0.9 u / ml to 9.9 u / ml ( figure 1 ) .
concentrations ranged from 0.022 ng / ml to 0.721 ng / ml and the mean was 0.076 ng / ml ( figure 2 ) .
there was no significant correlation between the amniotic fluid insulin or c - peptide values and different delivery modes ( figure 3 ) .
regarding the newborn birth weight , there was no correlation with amniotic fluid insulin or c - peptide ( figure 4 ) .
the concentrations of amniotic fluid insulin and c - peptide were compared with the collected birth injuries data ( e.g. perineal tears grade i to iii , effects on the clitoris , labia , or vaginal tears ) ( figure 5 ) .
only 10 patients had delivery complications . these were fever in 3 cases , major postpartum bleeding in 3 cases , 1 case with intraoperative complications , and 3 cases without complications . between the group with complications and the control group
there was no significant difference in amniotic fluid insulin or c - peptide ( figure 6 ) .
according to the pedersen hypothesis , maternal hyperglycemia caused by a gdm leads to fetal hyperglycemia and hence to fetal hyperinsulinism .
analyzed age - dependent insulin secretion and -cell number of the fetal pancreas in diabetic and non - diabetic women and found significant fetal -cell hypertrophia in diabetic women .
the amniotic fluid insulin is of fetal origin . during pregnancy , glucosuria , polyhydramnios , and fetal macrosomia
the german society of obstetrics and gynecology ( dggg ) suggests screening for gdm , which was established in december 2011 .
the hapo 2008 study showed a distinct correlation between increased maternal blood glucose and fetal outcome , especially macrosomia and shoulder dystocia , which led to adaptation of thresholds for the ogt in venous blood plasma .
because a predictive or early detection marker for the development of a gdm would be beneficial to indicate increased risk as soon as the early second trimester , several authors examined the correlation between amniotic fluid glucose , insulin , and c - peptide .
glucose is transported through the placenta , whereas amniotic fluid insulin is believed to be produced by the fetus . as
pregnancy progresses , insulin levels increase . in a population of 39 patients with gdm and 194 control - patients , star et al . showed a significant correlation between gdm and increased amniotic fluid insulin in amniocenteses at 14 to 20 weeks gestation .
for the study , we included 77 control patients and 9 patients with gdm who underwent amniocentesis between 15 and 22 weeks gestation .
carpenter et al . provided evidence for increased amniotic fluid insulin in patients who developed gdm later on .
in contrast to this , our group could not find any correlation between amniotic fluid insulin or c - peptide and the development of a gdm in a prospective study including 90 patients .
multiple investigators ( hapo2009 ) have found an association between gdm and fetal macrosomia , as well as increased rates of caesarean sections , birth injuries , and delivery complications . until recently , the german obstetrical guidelines did not include a general screening for gdm .
therefore , we investigated whether there is an association between amniotic fluid insulin or c - peptide as markers for fetal glucose metabolism and the development of gdm - complications such as fetal macrosomia , delivery complications , and birth injuries . to eliminate treatment for diabetes as a confounding factor
we retrospectively analyzed frozen amniotic fluid samples of 144 patients and could not find correlations between amniotic fluid insulin or c - peptide with fetal macrosomia , delivery mode , and birth complications or injuries . measuring the amniotic fluid insulin and c - peptide in the early amniocentesis seems to be unsuitable for prediction of gdm complications .
the role of these proteins for the prediction of a gdm developing later during pregnancy remains to be determined .
backgroundgestational diabetes mellitus ( gdm ) occurs in 35% of all pregnancies . 
 gdm increases both maternal and fetal risks , causes fetal macrosomia , and hence increases the rates of caesarean sections and delivery complications such as shoulder dystocia . 
 an early predictive marker and consequent early treatment could be beneficial , so amniotic fluid insulin and c - peptide have been examined in several studies . 
 increased amniotic fluid insulin in early amniocentesis between the 14th and 20th gestational week predicted a later gdm . 
 a potential direct association with fetal macrosomia remains to be determined.material/methodsthis retrospective study investigated amniotic fluid insulin / c - peptide from amniocenteses between 14 and 20 weeks of gestation in correlation with fetal birth weight , type of delivery , and complications . to focus on effects of fetal hyperinsulinism apart from therapeutic confounders 
 , we included patients who did not participate in gdm screening . 
 insulin and c - peptide were measured in 144 samples of frozen amniotic fluid . 
 birth weight , type of delivery , complications , and birth injuries were noted.resultsbirth weights ranged from 760 g to 4410 g with a mean weight of 3424 g at an average of 40 weeks gestation . 
 the mean amniotic fluid insulin was 4.36 u / ml and the mean c - peptide concentration was 0.076 ng / ml . there was no correlation between amniotic fluid insulin or c peptide and birth weight , type of delivery , complications , and birth injuries.conclusionsamniotic fluid insulin and c - peptide are unsuitable as predictive marker for fetal macrosomia , type of delivery , complications , or birth injuries .