Correlation Study Of Between Isolated Term Oligohydramnios With Pregnancy Outcome And Placental Pathology

BackgroundIsolated term oligohydramnios（ITO）is defined as the absence of fetal growth restriction,structure or chromosome abnormality,and other known maternal diseases（such as pre-eclampsia）,manifestation of decreased amniotic fluid at term^[1,2].Studies have shown that isolated oligohydramnios at term may be the first sign of placental dysfunction^[3],closely related to maternal and fetal outcomes,or may lead to an increased risk of termination of pregnancy,induced labor,and cesarean section,affect the incidence and mortality of perinatal infants^[4].Therefore,it is of great significance to further understand the relationship between ITO and placental pathology and its effect on mother and infant,to find reliable prenatal examination methods and to solve the difficult problems in the clinical work of obstetrics and gynecology.ObjectiveA retrospective study was conducted to collect general clinical data,pregnancy outcomes,neonatal outcomes,fetal ultrasound blood flow indicators,and placental tissue pathological results of ITO pregnant women and normal pregnant women admitted and delivered in our hospital’s obstetrics department.The comparison of ITO and normal pregnant women’s clinical outcomes（fetal blood flow,pregnancy outcome,placental histopathological results）can provide the basis for the intervention of ITO.Date and methods1.Study subjects:Retrospectively collected full-term singleton mothers delivered in the obstetrics department of Henan Provincial People’s Hospital from October 2019 to November 2022.ITO inclusion criteria:ultrasound examination of amniotic fluid index（AFI）≤50mm,gestational weeks 37-41⁺⁶weeks,single pregnancy,prenatal ultrasound estimation of non macrosomia,delivery in our hospital,after delivery,the placental tissue was examined by placental histopathology by the pathology department;Exclusion criteria:polyhydramnios,premature rupture of membranes,scarred uterus,hypertension during pregnancy,fetal structural developmental malformations,twin or multiple pregnancies,intrauterine growth restriction,gestational diabetes mellitus,other diseases associated with pregnancy,such as appendicitis,pancreatitis,cardiovascular disease,antiphospholipid syndrome,thrombophilia,systemic lupus erythematosus,etc.A total of 358 mothers were finally included,including 178 in the isolated term oligohydramnios group and180 in the normal amniotic fluid group,and their general data,mode of delivery,neonatal outcome and placental histopathological results were collected.This study has been approved by the hospital ethics committee.2.Research method:All women were divided into two groups according to amniotic fluid index:Isolated term oligohydramnios（ITO）group（N=178）and normal amniotic fluid（NAF）group（N=180）.ITO group was divided into good pregnancy group（n=159）and poor pregnancy group（N=19）according to different pregnancy outcomes.The general conditions of parturients include:Age,whether they are old parturients,the way of conception,the parity,the history of previous bad pregnancy and childbirth;Maternal pregnancy outcome indicators:delivery weeks,delivery mode（cesarean section,transfer cesarean section,selective induction of labor）,amniotic fluid pollution;Neonatal outcome:neonatal weight,5 min apgar<7 ratio,NICU occupancy rate,full-term low birth weight,fetal distress,perinatal mortality,and compound adverse outcomes.By comparing the two groups of general conditions and maternal and infant outcomes,to analyze the impact of ITO on maternal and infant outcomes and other related factors.The parameters of fetal blood flow included:The fetal middle cerebral artery blood flow resistance index,fetal middle cerebral artery pulsation index,fetal umbilical artery blood flow resistance index,fetal umbilical artery pulsation index,fetal umbilical artery systolic peak flow rate/end diastolic flow rate.The statistical indexes of placental pathological results included:Placental weight,abnormal insertion point of umbilical cord,too short umbilical cord,torsion of umbilical cord,the widest diameter of umbilical cord,placental pathological conditions（infarction,saponification,hematoma,etc.）.3.Statistical methods:SPSS 26.0 was used to analyze the data.Mean±standard deviation（SD）was used for normality test measurement data,and independent sample t-test was used for comparison between groups data that did not conform to the normal distribution were presented as median（quartile）,and Mann-whitney U test was used for comparison between groups.The categorical count data were expressed by the number of cases（percentage）,and theΧ²test was used for the comparison between groups.The test levels were all P<0.05 with statistical significance.Using Graphpad Prism to draw a forest map to analyze the related factors that affect the outcome of complex adverse neonatal outcomes.Results（1）General condition:The proportion of primipara:143 cases（80.3%）in ITO group and 124 cases（68.9%）in NAF group.The proportion of primipara in ITO group was higher than that in NAF group（P<0.05）.Maternal age:ITO group（31.65±3.88）,NAF group（31.51±3.32）.The mean age of ITO group was slightly higher than that of NAF group,but there was no significant difference（P=0.702）,there was no significant difference in the proportion of pregnant women over 35 years of age,conception mode（natural conception or assisted reproduction）,history of adverse pregnancy and delivery between Ito and NAF groups.（2）Pregnancy outcome:There was no significant difference between the two groups in the gestational weeks of delivery（P=0.354）.The rate of cesarean section was 69 cases（38.8%）in ITO group and 38 cases（21.1%）in NAF group.The rate of cesarean section in ITO group was higher than that in NAF group（P<0.05）.The rate of transferring cesarean section and selective abortion in ITO group were significantly higher than those in NAF group（P<0.05）.Amniotic fluid contamination:41 cases（23%）in ITO group and 22 cases（12.2%）in NAF group.The amniotic fluid contamination rate in ITO group was significantly higher than that in NAF group（P<0.05）.（3）Perinatal outcome:There were no neonatal deaths in both ITO group and NAP group.There was no significant difference in Apgar<7 at 5 min（P=0.990）.Neonatal weight（g）:ITO group（3136.18±304.47）,NAF group（3309.89±262.43）,the mean weight of ITO group was lower than that of NAF group（P<0.05）.The proportion of full-term low birth weight infants（P=0.021）,fetal distress（P=0.032）,and the incidence of composite neonatal adverse outcomes（P=0.003）in the ITO group were significantly higher than those in the NAF group（P<0.05）.The incidence of NICU occupancy in the ITO group was not significantly different from that in the NAF group（P>0.05）.（4）Analysis of factors related to adverse outcomes in newborns:Isolated term oligohydramnios and full-term low birth weight infants were significantly associated with the adverse outcomes（P<0.05）,however,amniotic fluid pollution,maternal age and history of adverse pregnancy and delivery were not significantly associated with adverse outcome of the combined newborn（P>0.05）.（5）Fetal blood flow parameters:There were significant differences in fetal umbilical artery blood flow resistance index（UA-RI）,fetal umbilical artery pulsation index（UA-PI）,fetal umbilical artery systolic peak flow rate/end diastolic flow rate（UA-S/D）,fetal middle cerebral artery blood flow resistance index（MCA-RI）,and fetal middle cerebral artery pulsation index（MCA-PI）between ITO and NAF pregnant women（P<0.05）.According to the neonatal outcome in ITO group,they were divided into good pregnancy outcome group and bad pregnancy outcome group,there were significant differences in MCA-RI,MCA-PI,UA-RI,UA-PI,UA-S/D between good pregnancy outcome and poor pregnancy outcome group（P<0.05）.（6）The placental weight（g）:ITO group（452.33±23.48）,NAF group（471.84±12.47）,the widest diameter of umbilical cord（mm）:ITO group（1.17±0.26）,NAF group（1.28±0.29）,compared with NAF group,ITO group had significantly smaller placental mass and narrower umbilical cord（P<0.05）,there were significant differences between the two groups in abnormal insertion point of the umbilical cord,infarction,chorioamnionitis,chorioocclusive endoangitis,choriothrombotic hematoma and fibrin deposition in chorionic space（P<0.05）.There was no significant difference between the two groups in focal calcification（P=0.854）,umbilical cord too short（P=0.670）and umbilical cord torsion（P=0.275）.Conclusions1.ITO may be significantly correlated with adverse perinatal outcome,high induced labor rate and cesarean section rate.2.There are significant differences in ultrasound blood flow between different pregnancy outcomes in ITO,indicating that prenatal ultrasound detection of fetal blood flow is beneficial for clinical evaluation of oligohydramnios fetal outcomes.3.The comparison of placental pathology between ITO and normal amniotic fluid indicates that ITO may be a part of“Placental insufficiency”.