Maternal Oxygen Research Articles

Evaluation of an Initiative to Decrease the Use of Oxygen Supplementation for Category II Fetal Heart Rate Tracings.

To examine compliance with a guideline to reduce exposure to supplemental oxygen for category II fetal heart rate (FHR) tracings in normally oxygenated laboring patients. All patients in labor in an urban academic medical center from January 1 to July 31, 2020 were assessed. The preintervention group included those who delivered from January 1 to March 19, 2020. On March 20, 2020, a new guideline took effect that recommended no maternal supplemental oxygen for category II FHR tracings. The postintervention group delivered from March 20 to July 31, 2020. Exclusion criteria were planned cesarean delivery, multiple gestations, delivery at less than 24 weeks of gestation, intrauterine fetal death, and patients who received supplemental oxygen for an oxygen saturation lower than 95%. The primary outcome was the percentage of patients who received oxygen in labor analyzed by control charts and the rules of special cause variation. Chi-squared and t tests were used for secondary outcome assessment. P<.05 was considered significant. A total of 1,333 patients were included, 474 patients in the preintervention group and 859 in the postintervention group. Oxygen was administered to 22.6% of patients before guideline implementation, compared with 0.6% after the guideline. Special cause variation was detected with an 8-point shift starting the month that the guideline was implemented, indicating statistical significance. There were no differences in any studied secondary maternal or fetal outcomes, although our statistical power to detect differences in infrequent outcomes was limited. This quality-improvement study demonstrated significant adherence to the guideline that supplemental oxygen would no longer be given to patients with category II FHR tracings in the absence of maternal hypoxemia, with no significant change in maternal or perinatal outcomes.

Maternal Oxygen Supplementation Compared With Room Air for Intrauterine Resuscitation: A Systematic Review and Meta-analysis

(Abstracted from JAMA Pediatr 2021;175:368–376) In the United States, 2 of 3 pregnant women receive oxygen supplementation at some point during labor. It is provided to increase placental oxygen transfer and prevent neonatal acidemia when fetal heart rate (FHR) tracings suggest fetal hypoxia.

P-084. Symptomatic SARS-COV-2 infected pregnant patients and preeclampsia: worse outcome?

Background/objectives: Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) infection and preeclampsia may share some common pathophysiological ground, as the inflammatory changes they impose. Although the clinical course of SARS COV-2 during pregnancy is not completely understood, recent findings suggest an increased risk of preeclampsia with severe features induced by viral infection. The aim of this study is to describe the clinical course of infected pregnant women who developed preeclampsia (PE). Methods: Cohort study of SARS-COV-2 PCR positive symptomatic pregnant patients, with (n=9) and without PE (n=45), followed from admission to hospital discharge. Clinical course, delivery, neonatal and maternal outcomes were analyzed. Results: SARS-Cov-2 women with PE had higher body mass index (41,3 ± 7,8kg/m2 vs 31,6 ± 6,2kg/m2;p<0,001) and higher level of d-dimers (3,47 ± 089 vs 1,97 ± 1,18;p 0,014) than their counterpart without PE. Delivery for maternal deterioration status was also more often in PE group (23,3% vs 75%;p 0,011). No differences were observed in rates of maternal intensive care admission, need of mechanical ventilation, pulmonary image findings, maternal oxygen saturation, gestational age of delivery or neonatal outcomes. Conclusions: Development of preeclampsia in symptomatic SARS-COV-2 infected pregnant women was associated with a higher rate of maternal-indicated deliveries. No differences were found regarding neonatal or maternal clinical outcomes.

The Effect of Intrapartum Oxygen Supplementation on Category II Fetal Monitoring

(Am J Obstet Gynecol. 2020;223:905.e1–905.e7) While oxygen is routinely administered in response to category II electronic fetal monitoring (EFM) patterns, there is not currently any evidence that this practice is beneficial for the neonate. Maternal oxygen supplementation in this context is meant to reduce fetal hypoxia, but a recent study suggests umbilical artery lactate was not improved with oxygen supplementation compared with therapy using room air (RA). This was a secondary analysis of that study, aimed at investigating how oxygen supplementation affects other markers of category II EFM.

Intrapartum Resuscitation Interventions for Category II Fetal Heart Rate Tracings and Improvement to Category I.

To evaluate intrapartum resuscitation interventions and improvement in category II fetal heart rate (FHR) tracings. This secondary analysis of a randomized trial of intrapartum fetal electrocardiographic ST-segment analysis included all participants with category II FHR tracings undergoing intrauterine resuscitation: maternal oxygen, intravenous fluid bolus, amnioinfusion, or tocolytic administration. Fetal heart rate pattern-recognition software was used to confirm category II FHR tracings 30 minutes before intervention and to analyze the subsequent 60 minutes. The primary outcome was improvement to category I within 60 minutes. Secondary outcomes included FHR tracing improvement to category I 30-60 minutes after the intervention and composite neonatal outcome. Of 11,108 randomized participants, 2,251 (20.3%) had at least one qualifying intervention for category II FHR tracings: 63.7% improved to category I within 60 minutes and 50.5% improved at 30-60 minutes. Only 3.4% underwent cesarean delivery and 4.1% an operative vaginal delivery for nonreassuring fetal status within 60 minutes after the intervention. Oxygen administration was the most common intervention (75.4%). Among American College of Obstetricians and Gynecologists-defined subgroups that received oxygen, the absent FHR accelerations and absent-minimal FHR variability subgroup (n=332) was more likely to convert to category I within 60 minutes than the FHR accelerations or "moderate FHR variability" subgroup (n=1,919) (77.0% vs 63.0%, odds ratio [OR] 2.0, 95% CI 1.4-2.7). The incidence of composite neonatal adverse outcome for category II tracings was 2.9% (95% CI 2.2-3.7%) overall; 2.8% (95% CI 2.0-3.8%) for improvement to category I within 60 minutes (n=1,433); and 3.2% (95% CI 2.1-4.6%) for no improvement within 60 minutes (n=818). However, the group with improvement had 29% lower odds for higher level neonatal care (11.8% vs 15.9%, OR 0.71, 95% CI 0.55-0.91). Nearly two thirds of category II FHR tracings improved to category I within 60 minutes of intervention with a relatively low overall rate of the composite neonatal adverse outcome. Funded in part by Neoventa Medical.

Effect and Safety of Remifentanil Patient-Controlled Analgesia Compared with Epidural Analgesia in Labor: An Updated Meta-Analysis of Randomized Controlled Trials

Purpose: The study was aimed to systematically assess the effect and safety of remifentanil patient-controlled analgesia (rPCA) versus epidural analgesia (EA) during labor. Methods: Eligible trials were retrieved from PubMed, EMBASE, ScienceDirect, and Cochrane Library before April 2020. The primary outcomes were patient satisfaction with pain relief and average visual analog scale (VAS) pain scores during labor; the secondary outcomes were rate of spontaneous delivery, oxygen desaturation, maternal hyperthermia, and neonatal Apgar scores <7 at 1 and 5 min. Results: Eleven studies involving 3,039 parturients were included. We found that parturients receiving rPCA were similarly satisfied with pain relief compared to those receiving EA (standardized mean difference: −0.19; 95% confidence interval [CI]: −0.57, 0.18), though had significantly higher VAS pain scores during labor (weighted mean difference: 1.41; 95% CI: 0.32, 2.50). The rate of spontaneous delivery was comparable. rPCA increased the risk of maternal oxygen desaturation (risk ratio [RR]:3.23, 95% CI: 1.98, 5.30). There was no statistical significance regarding hyperthermia (RR: 0.49, 95% CI: 0.24, 1.01). No significant difference was found for neonatal Apgar scores <7 at 1 and 5 min. Conclusion: rPCA could be an optional alternative for pain relief to EA without worsening maternal satisfaction with pain relief, delivery modes, or neonatal morbidity. However, rPCA was associated with higher pain intensity during labor and higher incidence of maternal oxygen desaturation. The routine use of rPCA in labor must be armed with close respiratory monitoring. Continued well-designed studies are required to provide more robust evidence.

Does wearing double surgical masks during the COVID-19 pandemic reduce maternal oxygen saturation in term pregnant women?: A prospective study.

PurposeThis study aimed to compare the effects of using single and double surgical masks (SM) on maternal oxygen saturation in pregnant women.MethodsIn this prospective study, single or double SM were worn by term pregnant women who applied for routine controls. The vital signs of the participants such as oxygen saturation, pulse, respiratory rate, fever, systolic and diastolic blood pressure were measured at admission and 30 min later.ResultsThere were 223 participants in the single SM group and 231 participants in the double SM group. Thirty minutes after putting on the mask, there was no significant difference in the proportion of patients whose oxygen saturation fell below 95 (3.6 vs 5.6%, p = 0.301). No significant difference was observed between the admission and 30 min oxygen saturation levels of the pregnant women in the single SM group. However, maternal oxygen saturation after 30 min of the pregnant women in the double SM group was significantly lower (97.4 ± 1.1 vs 96.6 ± 1.3, p < 0.001). No significant changes were observed in the vital signs of either groups.ConclusionWhen using double SM, oxygen saturation is significantly reduced compared to pre-mask values. Nevertheless, it seems difficult to say that these decreases have clinical significance.

Comprehensive pregnancy monitoring with a network of wireless, soft, and flexible sensors in high- and low-resource health settings

Vital signs monitoring is a fundamental component of ensuring the health and safety of women and newborns during pregnancy, labor, and childbirth. This monitoring is often the first step in early detection of pregnancy abnormalities, providing an opportunity for prompt, effective intervention to prevent maternal and neonatal morbidity and mortality. Contemporary pregnancy monitoring systems require numerous devices wired to large base units; at least five separate devices with distinct user interfaces are commonly used to detect uterine contractility, maternal blood oxygenation, temperature, heart rate, blood pressure, and fetal heart rate. Current monitoring technologies are expensive and complex with implementation challenges in low-resource settings where maternal morbidity and mortality is the greatest. We present an integrated monitoring platform leveraging advanced flexible electronics, wireless connectivity, and compatibility with a wide range of low-cost mobile devices. Three flexible, soft, and low-profile sensors offer comprehensive vital signs monitoring for both women and fetuses with time-synchronized operation, including advanced parameters such as continuous cuffless blood pressure, electrohysterography-derived uterine monitoring, and automated body position classification. Successful field trials of pregnant women between 25 and 41 wk of gestation in both high-resource settings (n = 91) and low-resource settings (n = 485) demonstrate the system's performance, usability, and safety.

Impact of intrauterine fetal resuscitation with oxygen on oxidative stress in the developing rat brain

Use of maternal oxygen for intrauterine resuscitation is contentious because of the lack of evidence for its efficacy and the possibility of fetal harm through oxidative stress. Because the developing brain is rich in lipids and low in antioxidants, it remains vulnerable to oxidative stress. Here, we tested this hypothesis in a term pregnant rat model with oxytocin-induced fetal distress followed by treatment with either room air or 100% oxygen for 6 h. Fetal brains from both sexes were subjected to assays for biomarkers of oxidative stress (4-hydroxynonenal, protein carbonyl, or 8-hydroxy-2ʹ-deoxyguanosine), expression of genes mediating oxidative stress, and mitochondrial oxidative phosphorylation. Contrary to our hypothesis, maternal hyperoxia was not associated with increased biomarkers of oxidative stress in the fetal brain. However, there was significant upregulation of the expression of select genes mediating oxidative stress, of which some were male-specific. These observations, however, were not accompanied by changes in the expression of proteins from the mitochondrial electron transport chain. In summary, maternal hyperoxia in the setting of acute uteroplacental ischemia-hypoxia does not appear to cause oxidative damage to the developing brain.

The Effect of Intrapartum Oxygen Supplementation on Category II Fetal Monitoring

(Abstracted from Am J Obstet Gynecol 2020;223:905.e1–905.e7) The administration of maternal oxygenation (O2) is a commonly used resuscitation technique for fetuses with category II electronic fetal monitoring (EFM) patterns. In cases of recurrent fetal decelerations, the goal of maternal O2 supplementation is to increase fetal oxygenation.

Nifedipine disturbs fetal cardiac function during hypoxemia in a chronic sheep model at near term gestation

Nifedipine is a widely used drug in pregnancies complicated by maternal hypertensive disorders that can be associated with placental insufficiency and fetal hypoxemia. The evidence regarding fetal myocardial responses to nifedipine in hypoxemia is limited. We hypothesized that nifedipine would not impair fetal sheep cardiac function under hypoxemic environment. In particular, we investigated the effects of nifedipine on fetal ventricular functional parameters and cardiac output. A total of 21 chronically instrumented fetal sheep at 122 to 134 gestational days (term, 145 days) were included in this study. Fetal cardiac function was evaluated by measuring global longitudinal strain, indices describing ventricular systolic and diastolic function, and cardiac outputs using two-dimensional speckle tracking and tissue and spectral pulsed-wave Doppler echocardiography. Fetal carotid artery blood pressure and blood gas values were invasively monitored. After baseline data collection, fetal hypoxemia was induced by maternal hyperoxygenation. After hypoxemia phase data collection, 9 fetuses received nifedipine infusion, and 12 fetuses received saline infusion. Data were collected 30 and 120 minutes after the infusion was started. After 120 minutes of data collection, maternal and fetal oxygenation were normalized, and normoxemia phase data were collected, while infusion was continued. Hypoxemia decreased fetal carotid artery mean arterial pressure from 40 (8) mm Hg to 35 (8) mm Hg (P<.007), and left ventricular global longitudinal strain showed less deformation than at baseline (P=.001). Under hypoxemia, nifedipine caused a reduction in right ventricular global longitudinal strain (P<.05), a decrease in right ventricular isovolumic relaxation velocity and its deceleration (P<.01) indicating diastolic dysfunction, and a drop in right ventricular cardiac output (P<.05). Nifedipine did not alter fetal left ventricular functional parameters or cardiac output. When normoxemia was restored, fetal right ventricular functional parameters and cardiac output returned to baseline level. In hypoxemic fetus, nifedipine impaired right ventricular function and reduced its cardiac output. The detrimental effects of nifedipine on fetal right ventricular function were abolished, when normoxemia was restored. Our findings suggest that in a hypoxemic environment nifedipine triggers detrimental effects on fetal right ventricular function.

Magnesium sulfate titration reduces maternal complications following fetoscopic closure of spina bifida.

To evaluate if magnesium sulfate (MgSO4 ) titration following fetoscopic spina bifida closure is associated with fewer maternal complications than the Management of Myelomeningocele Study (MOMS) tocolytic regimen. This prospective cohort study included 73 consecutive patients undergoing fetoscopic closure of spina bifida between 2015 and 2020. A policy of using the MgSO4 regimen per the MOMS trial was changed to a flexible one in which MgSO4 was titrated according to the frequency of the uterine contractions following surgery. The frequency of maternal pulmonary edema, low maternal oxygen saturation requiring oxygen supplementation, atelectasis, hypocalcemia, and preterm delivery was compared before and after the policy was changed. A higher proportion of women in the group that used the MOMS MgSO4 regimen had pulmonary edema compared to those in the flexible one (26.1% [6/23] vs. 6% [3/50]; p=0.024). Multivariate analysis showed that the MOMS tocolytic regimen was independently associated with a higher risk of pulmonary edema (adjusted odds ratio: 8.57; 95% confidence interval: 1.54-47.7; p=0.014) than a flexible one. There was no difference in the rate of preterm delivery. Following fetoscopic closure of spina bifida, the MOMS MgSO4 regimen is associated with an increased risk of pulmonary edema than a more flexible regimen.

For which patients is maternal oxygen supplementation of value?

For which patients is maternal oxygen supplementation of value?

896 The effect of maternal hyper-oxygenation on vascular resistance of growth restricted fetuses

To study the effects of maternal hyper-oxygenation on fetal circulation as measured by Doppler ultrasonography in the growth restricted fetus. This is prospective observational study. Patients were positioned in low-fowlers position with the head of the bed elevated between 15 and 30 degrees for approximately 15 minutes. 100% oxygen was delivered at a flow rate of 8 l/min through a close-fitting facemask (with a reservoir and non-rebreathing valve) for a duration of 10 minutes. Fetal doppler ultrasonography was performed 20 minutes prior and after administration of supplemental oxygen. Doppler values for umbilical artery, middle cerebral artery, ductus venosus, were obtained during a period of fetal apnea, preferably fetal quiet sleep as flow waveforms and cardiac output have been shown to vary with behavioral states. At least three consecutive waveforms were gathered. Six patients with growth restricted fetuses were enrolled. We found no statistically signficant differences in umbilical artery peak systolic flow, end diastolic flow, resistance index, pulsatility index. or systolic to diastolic ratio before and after maternal hyper-oxygenation. We also found no difference in middle cerebral artery peak systolic flow, end diastolic flow, resistance index, and pulsatility index before and after maternal hyper-oxygenation. We were unable to measure fetal ductus venosus doppler flow due to hyperactivity of the fetus within the 20 minutes following maternal oxygen administration. Maternal hyper-oxygenation caused a noted increase in fetal movements in the growth restricted fetus, and precluded aquisition of fetal ductus venosus assessement following oxygen administration. We found no significant differences in umbilical artery and middle cerebral artery doppler flow measurements following maternal hyper-oxygenation.

Evaluation of placental oxygenation index using blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) during normal late pregnancy

Aim Noninvasive blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) has recently been used to evaluate placental oxygenation. However, this method still has unresolved problems, such as long testing times and lack of normal values set. In the present study, we used a shorter protocol in BOLD-MRI and established normal values for placental oxygenation in late pregnancy. Methods We recruited 18 healthy singleton pregnant women (>32 weeks of gestation) who had a normal body size before pregnancy and a normal course of pregnancy. They underwent BOLD-MRI with three consecutive 4-min periods of different oxygenation: normoxia (21% O2), hyperoxia (10 L O2/min), and then normoxia. Placental time–activity curves were presented as signal intensity change relative to baseline (ΔR2*). The time from starting maternal oxygen administration to peak ΔR2*. To assess the relationship between peak ΔR2* values and placenta-related parameters and fetal development, the correlation between peak ΔR2*, placental weight, and neonatal birth weight was evaluated using Spearman’s rank correlation test. Results In all cases, the BOLD signal was elevated by maternal oxygen administration, with the peak resolving within 4 min after the end of oxygen administration. Peak ΔR2* and time to peak ΔR2* during oxygenation were 7.99 ± 2.58, and 458.1 ± 73.9 s, respectively. There was a significant correlation between peak ΔR2* and neonatal birth weight (percentile) (r = 0.537, p = .022), and between placental weight and neonatal birth weight (r = 0.769, p < .01). Conclusions In all cases, the BOLD signal increased with maternal hyperoxia using this protocol. So, 4 min observation following maternal oxygen administration is sufficient for peak ΔR2* evaluation. These reference values set in this study may be one of the indicators of BOLD signal changes in normal pregnancies after 32 weeks of gestation.

Maternal Oxygen Supplementation Compared With Room Air for Intrauterine Resuscitation

Supplemental oxygen is commonly administered to pregnant women at the time of delivery to prevent fetal hypoxia and acidemia. There is mixed evidence on the utility of this practice. To compare the association of peripartum maternal oxygen administration with room air on umbilical artery (UA) gas measures and neonatal outcomes. Ovid MEDLINE, Embase, Scopus, ClinicalTrials.gov, and Cochrane Central Register of Controlled Trials were searched from February 18 to April 3, 2020. Search terms included labor or obstetric delivery and oxygen therapy and fetal blood or blood gas or acid-base imbalance. Studies were included if they were randomized clinical trials comparing oxygen with room air at the time of scheduled cesarean delivery or labor in patients with singleton, nonanomalous pregnancies. Studies that did not collect paired umbilical cord gas samples or did not report either UA pH or UA Pao2 results were excluded. Data were extracted by 2 independent reviewers. The analysis was stratified by the presence or absence of labor at the time of randomization. Data were pooled using random-effects models. The primary outcome for this review was UA pH. Secondary outcomes included UA pH less than 7.2, UA Pao2, UA base excess, 1- and 5-minute Apgar scores, and neonatal intensive care unit admission. The meta-analysis included 16 randomized clinical trials (n = 1078 oxygen group and n = 974 room air group). There was significant heterogeneity among the studies (I2 = 49.88%; P = .03). Overall, oxygen administration was associated with no significant difference in UA pH (weighted mean difference, 0.00; 95% CI, -0.01 to 0.01). Oxygen use was associated with an increase in UA Pao2 (weighted mean difference, 2.57 mm Hg; 95% CI, 0.80-4.34 mm Hg) but no significant difference in UA base excess, UA pH less than 7.2, Apgar scores, or neonatal intensive care unit admissions. Umbilical artery pH values remained similar between groups after accounting for the risk of bias, type of oxygen delivery device, and fraction of inspired oxygen. After stratifying by the presence or absence of labor, oxygen administration in women undergoing scheduled cesarean delivery was associated with increased UA Pao2 (weighted mean difference, 2.12 mm Hg; 95% CI, 0.09-4.15 mm Hg) and a reduction in the incidence of UA pH less than 7.2 (relative risk, 0.63; 95% CI, 0.43-0.90), but these changes were not noted among those in labor (Pao2: weighted mean difference, 3.60 mm Hg; 95% CI, -0.30 to 7.49 mm Hg; UA pH<7.2: relative risk, 1.34; 95% CI, 0.58-3.11). This systematic review and meta-analysis suggests that studies to date showed no association between maternal oxygen and a clinically relevant improvement in UA pH or other neonatal outcomes.

Quality of vital sign monitoring during obstetric hospitalizations at a regional referral and teaching hospital in Uganda: an opportunity for improvement.

Introductionvital sign monitoring is a key component of safe facility-based obstetric care. We aimed to assess quality of care around vital sign monitoring during obstetric hospitalizations in a tertiary-care facility in a resource-limited setting.Methodsretrospective review of obstetric records at a tertiary care facility. We assessed documentation of vital signs including fetal and maternal heart rate, and maternal blood pressure, temperature, oxygen saturation and urine output. The primary outcome was the quality of vital sign monitoring (high- versus low-quality based on frequency of monitoring). We compared quality of monitoring with timing of admission, presence of complication, and delivery mode using chi-squared tests.Resultsamong 360 records of obstetric admissions (94% of a planned random sample), 96% documented a delivery. Of these, 8% of pregnant women and 11% of postpartum women had high-quality vital sign monitoring documented on initial evaluation at admission. For women delivering during the hospitalization, 0.8% of women delivering had high-quality monitoring in the first four hours postpartum, with higher rates of high-quality monitoring in women delivering vaginally compared to those delivered by cesarean (1.4% versus 0%, p<0.001). There were no differences in rates of quality monitoring by time of admission, or obstetric complication.Conclusionvery few obstetric hospitalizations had high-quality vital sign monitoring. Attention towards improving vital sign monitoring is a critical need.

Maternal cardiac adaptation and fetal growth

Pregnancies with small-for-gestational-age fetuses are at increased risk of adverse maternal-fetal outcomes. Previous studies examining the relationship between maternal hemodynamics and fetal growth were mainly focused on high-risk pregnancies and those with fetuses with extreme birthweights, such as less than the 3rd or 10th percentile and assumed a similar growth pattern in fetuses above the 10th percentile throughout gestation. This study aimed to evaluate the trends in maternal cardiac function, fetal growth, and oxygenation with advancing gestational age in a routine obstetrical population and all ranges of birthweight percentiles. This was a prospective, longitudinal study assessing maternal cardiac output and peripheral vascular resistance by bioreactance at 11+0 to 13+6, 19+0 to 24+0, 30+0 to 34+0, and 35+0 to 37+0 weeks' gestation, sonographic estimated fetal weight in the last 3 visits and the ratio of the middle cerebral artery by umbilical artery pulsatility indices or cerebroplacental ratio in the last 2 visits. Women were divided into the following 5 groups according to birthweight percentile: group 1, <10th percentile (n=261); group 2, 10 to 19.9 percentile (n=180); group 3, 20 to 29.9 percentile (n=189); group 4, 30 to 69.9 percentile (n=651); and group 5, ≥70th percentile (n=508). The multilevel linear mixed-effects model was performed to compare the repeated measures of hemodynamic variables and z scores of the estimated fetal weight and cerebroplacental ratio. In visit 2, compared with visit 1, in all groups, cardiac output increased, and peripheral vascular resistance decreased. At visit 3, groups 1, 2, and 3, compared with 4 and 5, demonstrated an abrupt decrease in cardiac output and increase in peripheral vascular resistance. From visit 2, group 1 had a constant decline in estimated fetal weight, coinciding with the steepest decline in maternal cardiac output and rise in peripheral vascular resistance. In contrast, in groups 4 and 5, the estimated fetal weight had a stable or accelerative pattern, coinciding with the greatest increase in cardiac output and lowest peripheral vascular resistance. Groups 2 and 3 showed a stable growth pattern with intermediate cardiac output and peripheral vascular resistance. Increasing birthweight was associated with higher cerebroplacental ratio. Groups 3, 4, and 5 had stable cerebroplacental ratio across visits 3 and 4, whereas groups 1 and 2 demonstrated a significant decline (P<.001). In a general obstetrical population, maternal cardiac adaptation at 32 weeks' gestation parallels the pattern of fetal growth and oxygenation; babies with birthweight<20th percentile have progressive decline in fetal cerebroplacental ratio, decline in maternal cardiac output, and increase in peripheral vascular resistance.

The effect of mask use on maternal oxygen saturation in term pregnancies during the COVID-19 process.

Our aim was to evaluate the effect of standard surgical and N-95 respiratory mask use on maternal oxygen saturation, vital signs and result on non-stress tests in term pregnancies. It is a prospective observational study. The study included healthy, not in labor, singleton pregnant women of 370/7-410/7weeks who were applied to our hospital for routine obstetric control examination between March 1, 2020, and August 31, 2020. Patients were randomised by coin toss method. Oxygen saturation, systolic, and diastolic arterial blood pressure, pulse, respiratory rate, and temperature of pregnant women using surgical masks and respiratory masks were measured before and after the non-stress test. The tolerance of the masks was also evaluated. Student's t-test was used for variables showing parametric distribution and the Mann Whitney U-test was used for non-parametric tests. The categorical variables between the groups was analyzed by using the Chi square test or Fisher Exact test. The statistical significance level was taken as p<0.05 in all tests. A total of 297 pregnant women using masks were included in the study. The effect of mask type on oxygen saturation before and after the non-stress test was found to be significant (97.1±1.8 corresponds to 95.3±2.6 for the surgical mask, p=0.0001; 97.8±1.7 corresponds to 93.7±2.0 for the respiratory mask, p=0.0001). Mask tolerance of patients using respiratory masks was significantly higher than those using surgical masks (mean 8, 1-10, p=0.0001). Surgical mask and respiratory mask usage decreased significantly in oxygen saturation in term pregnancies.

The efficacy of high flow nasal oxygenation for maintaining maternal oxygenation during rapid sequence induction in pregnancy: A prospective randomised clinical trial.

High-flow nasal oxygenation (HFNO) for pre-oxygenation in rapid sequence induction (RSI) has only been assessed in volunteer parturients without intubation. To evaluate the efficacy of HFNO in comparison with the conventional facemask for oxygenation during RSI for caesarean section under general anaesthesia. Operating room in a tertiary hospital. Prospective randomised, controlled study. Thirty-four healthy parturients undergoing general anaesthesia for caesarean section. Parturients were randomly assigned to HFNO or standard facemask (SFM) group. The primary outcome measure was the PaO2 immediately after intubation. Secondary outcomes included lowest saturation throughout the intubation procedure, end-tidal oxygen concentration (EtO2) on commencing ventilation, blood gas analysis (pH, PaCO2), fetal outcomes and intubation-related adverse events. PaO2 in the HFNO group was significantly higher than that in SFM group (441.41 ± 46.73 mmHg versus 328.71 ± 72.80 mmHg, P < 0.0001). The EtO2 concentration in the HFNO group was higher than that in the SFM group (86.71 ± 4.12% versus 76.94 ± 7.74%, P < 0.0001). Compared to baseline, PaCO2 immediately after intubation also increased significantly in both groups (HFNO group: 30.87 ± 2.50 mmHg versus 38.28 ± 3.18 mmHg; SFM group: 29.82 ± 2.57 mmHg versus 38.05 ± 5.76 mmHg, P < 0.0001), but there was no difference in PaCO2 between the two groups. There was no difference in lowest saturation, intubation times, duration of apnoea, pH value or fetal outcomes. Compared with SFM, HFNO provided a higher PaO2 and EtO2 immediately after intubation in parturients. HFNO is safe as a method of oxygenation during RSI in parturients undergoing general anaesthesia for caesarean section. Clinical trial ChiCTR1900023121.