Five-year trends in maternal cardiac arrest in Maryland: 2013-2017.

BACKGROUND: The United States (US) maternal mortality rate (MMR) continues to increase. Until recently, the MMR in Maryland (MD) was consistently higher than the national average. Maternal cardiac arrest (MCA) is a rare condition, but can lead to devastating consequences. The incidence of MCA in the US is approximately 6-8 per 100,000 deliveries. To our knowledge there is no contemporary review of MCA in MD. Our primary aim was to determine the incidence of MCA in MD over a 5-year period. Secondary aims were to explore the causes of MCA, as well as characterize maternal and fetal survival. MATERIALS AND METHODS: Maternal cardiac arrests in Maryland were identified using diagnostic codes and a statewide administrative database for the fiscal years 2013 through 2017. MCA incidence and mortality rates were compared with previously reported national data from 1998 to 2011. Demographic characteristics, medical co-morbidities, obstetric complications, mode of delivery, and fetal outcomes were collected for all patients. The apparent cause of MCA was determined for each patient. Complications and procedures performed in MCAs were also recorded. RESULTS: In MD, 36 of 47 acute care hospitals provided maternity care. There were 32 cases of MCA in 332,483 deliveries, an estimated incidence rate of 10 per 100,000 deliveries (95% CI = 5-18). The most common apparent cause of MCA was hemorrhage. Maternal survival was 59.4%, while fetal survival was 93.8%. No significant differences were observed in MCA by age group. The incidence of MCA was significantly higher among non-Caucasian patients (24/177,727) when compared to Caucasian patients (8/154,732)(p =.01). DISCUSSION: Maternal cardiac arrest in Maryland appears to be comparable to the US average, with similar maternal survival rates. Non-Caucasian patients appear to have a disproportionately high rate of these complications. While maternal mortality is high for MCA, fetal survival is excellent. Continued efforts and attention are needed to prevent MCA in underserved minorities and treat postpartum hemorrhage, the leading contributor to MCA over the past decade.

Clinical Outcomes of Pregnant and Postpartum Extracorporeal Membrane Oxygenation Patients.

BACKGROUND: The use of extracorporeal membrane oxygenation (ECMO) as a rescue therapy for cardiopulmonary failure is expanding in critical care medicine. In this case series, we describe the clinical outcomes of 21 consecutive pregnant or postpartum patients that required venovenous (VV) or venoarterial (VA) ECMO. Our objective was to characterize maternal and fetal survival in peripartum ECMO and better understand ECMO-related complications that occur in this unique patient population. METHODS: Between January 2009 and June 2019, all pregnant and postpartum patients treated with ECMO for respiratory or circulatory failure at a single quaternary referral center were identified. For all patients, indications for ECMO, maternal and neonatal outcomes, details of ECMO support, and anticoagulation and bleeding complications were collected. RESULTS: Twenty-one obstetric patients were treated with ECMO over 10 years. Thirteen patients were treated with VV ECMO and 8 patients were treated with VA ECMO. Six patients were pregnant at the time of cannulation and 3 patients delivered while on ECMO; all 6 maternal and infant dyads survived to hospital discharge. The median gestational age at cannulation was 28 weeks (interquartile range [IQR], 24-31). In the postpartum cohort, ECMO initiation ranged from immediately after delivery up to 46 days postpartum. Fifteen women survived (72%). Major bleeding complications requiring surgical intervention were observed in 7 patients (33.3%). Two patients on VV ECMO required bilateral orthotopic lung transplantation and 1 patient on VA ECMO required orthotopic heart transplantation to wean from ECMO. CONCLUSIONS: Survival for mother and neonate are excellent with peripartum ECMO in a high-volume ECMO center. Neonatal and maternal survival was 100% when ECMO was used in the late second or early third trimester. Based on these results, ECMO remains an important treatment option for peripartum patients with cardiopulmonary failure.

Venovenous Extracorporeal Membrane Oxygenation to Prolong Pregnancy: A Case Report.

We report a gravida in fulminant acute respiratory distress syndrome, mechanically ventilated at 27 weeks estimated gestational age, who further deteriorated into severe combined hypercarbic, hypoxemic respiratory failure. At 30 weeks estimated gestational age, she was placed on venovenous extracorporeal membrane oxygenation (ECMO) because of refractory respiratory failure. Her physical status improved without fetal deterioration. She was managed expectantly in an effort to allow continued fetal maturation. Six days later, complications of ECMO (pulmonary hemorrhage) led to emergent abdominal delivery of a living male child. She was successfully weaned from ECMO 8 days later. The implications of ECMO during pregnancy are discussed.

Platelets in preeclamptic pregnancies fail to exhibit the decrease in mitochondrial oxygen consumption rate seen in normal pregnancies.

Cellular oxygen consumption and lactate production rates have been measured in both placental and myometrial cells to study obstetrics-related disease states such as preeclampsia. Platelet metabolic alterations indicate systemic bioenergetic changes that can be useful as disease biomarkers. We tested the hypothesis that platelet mitochondria display functional alterations in preeclampsia. Platelets were harvested from women in the third trimester of either a healthy, non-preeclamptic or preeclamptic pregnancy, and from healthy, non-pregnant women. Using Seahorse respirometry, we analyzed platelets for oxygen consumption (OCR) and extracellular acidification (ECAR) rates, indicators of mitochondrial electron transport and glucose metabolism, respectively. There was a 37% decrease in the maximal respiratory capacity measured in platelets from healthy, non-preeclamptic compared with preeclamptic pregnancy (P<0.01); this relationship held true for other measurements of OCR, including basal respiration; ATP-linked respiration; respiratory control ratio (RCR); and spare respiratory capacity. RCR, a measure of mitochondrial efficiency, was significantly lower in healthy pregnant compared with non-pregnant women. In contrast with increased OCR, basal ECAR was significantly reduced in platelets from preeclamptic pregnancies compared with either normal pregnancies (-25%; P<0.05) or non-pregnant women (-22%; P<0.01). Secondary analysis of OCR revealed reduced basal and maximal platelet respiration in normal pregnancy prior to 34 weeks' estimated gestational age (EGA) compared with the non-pregnant state; these differences disappeared after 34 weeks. Taken together, findings suggest that in preeclampsia, there exists either a loss or early (before the third trimester) reversal of a normal biologic mechanism of platelet mitochondrial respiratory reduction associated with normal pregnancy.

Liver lacerations as a complication of CPR during pregnancy.

AIM: Cardiac arrest in peripartum patients is a rare but devastating event; reported rates in the literature range from 0.019% to 0.0085%. In the general population, a well-described complication of cardiopulmonary resuscitation (CPR), liver laceration and injury, is reported at a rate of between 0.5-2.9% after CPR. Liver laceration rate among peripartum patients receiving CPR has not been well-studied. We sought to find the rate of liver lacerations in the peripartum population associated with CPR, with the hypothesis that the rate would be higher than in the general population. METHODS: We identified pregnancies complicated by cardiac arrest by performing a retrospective medical record review from 2011 to 2016 at a single tertiary referral hospital. We then compared the rate of liver lacerations in this group to the rate in the general population as found in the literature. RESULTS: Eleven of 9408 women in the peripartum period suffered cardiac arrest. Return of spontaneous circulation occurred in seven of eleven (64%) women. Three of these seven women suffered clinically significant liver laceration (43%). Overall mortality rate among women suffering cardiac arrest was 82% (9/11).Even after return of spontaneous circulation, the mortality rate was 72%(5/7) including two of three women suffering liver laceration. CONCLUSIONS: Based on a small retrospective study, liver lacerations requiring intervention occurred in 43% of gravidas patients that survived CPR, and is significantly higher than published rates (0.6-2.1%) for the general patient population. Further studies are indicated to determine the incidence of liver injury after peripartum CPR.

The Relationship between Rostral Retraction of the Pannus and Outcomes at Cesarean Section.

Objective Maternal obesity presents several challenges at cesarean section. In an effort to routinely employ a transverse suprapubic skin incision, we often retract the pannus in a rostral direction using adhesive tape placed after induction of anesthesia and before surgical preparation of the skin. We sought to understand the association between taping and neonatal cord blood gases, Apgar scores, and time from skin incision to delivery of the neonate. Study Design This is a retrospective study, performed using prospectively collected anesthesiology records with data supplemented from the patients' medical records. Singleton pregnancies with morbid obesity (body mass index [BMI] > 40 kg/m(2)) between 37 and 42 weeks of gestation who delivered via nonurgent, scheduled cesarean delivery under regional (spinal, combined spinal-epidural, or epidural) anesthesia between March 2007 and March 2013 were identified. Maternal demographics including BMI, comorbidities, type of anesthesia, time intervals during the surgery, cord gas results, and Apgar scores were collected. The relationship between taping and blood acid-base status, Apgar scores, and interval from skin incision to delivery was investigated using appropriate statistical tests. Results There were 2,525 (27.5%) cesarean deliveries out of 9,189 total deliveries. Applying the described inclusion/exclusion criteria, 141 patients were identified (33 taped and 108 nontaped). There was no significant difference in BMI between the taped (51.9 kg/m(2)) and nontaped groups (47.4 kg/m(2)), p > 0.05. There was no difference in type of anesthesia (p > 0.05). The only significant difference between the taped and not-taped groups was the presence of chronic hypertension in the taped group (p = 0.03). There were no significant differences in cord blood gas values, Apgar scores, or skin incision to delivery interval (p > 0.05 for all outcomes). Conclusions Taping of the pannus at cesarean section is a safe intervention that is not associated with adverse neonatal outcomes. Furthermore, over a set of parturients with BMI > 40 kg/m(2), it does not hasten skin incision to delivery time.

Anesthetic Implications of an Obstetric Patient with Blue Rubber Bleb Nevus Syndrome.

Blue rubber bleb nevus syndrome, a syndrome of multifocal venous malformations, has been reported rarely during pregnancy. This syndrome has been associated with airway lesions in some patients and neuraxial abnormalities in other patients. We report the anesthetic and obstetric management of a patient with an extensive distribution of both airway and neuraxial lesions.

Predictors of fetal growth in maternal HIV disease.

We sought to determine predictors of fetal growth restriction in maternal HIV disease. Pregnant HIV-positive women on antiretroviral therapy were monitored with serial viral load and CD4 counts. Individualized growth potential (GP) percentile was calculated for birth weight (BW). BW <10th GP percentile defined fetal growth restriction (FGR). Multiple medical and social factors, CD4 count, viral load, and antiretroviral therapy were tested for impact on fetal growth using chi-square and multiple regression analysis. Two hundred eleven women were studied. CD4 count <200 in the first trimester was strongly associated with FGR (odds ratio 8.75, 95% confidence interval 2.88 to 26.52). Maternal age ( P = 0.02) and smoking ( P = 0.03) were independent cofactors for FGR (Nagelkerke R(2) = 0.33). No other factors demonstrated an independent effect. Severity of maternal HIV disease as indicated by the CD4 count, rather than placental exposure to viral load, predicts FGR. Smoking has an independent detrimental effect on fetal growth.

Decreased placental oxygenation capacity in pre-eclampsia: clinical application of a novel index of placental function preformed at the time of delivery.

OBJECTIVE: We have previously described placental oxygenation capacity as an index of placental function. The aim of this study was to utilize this test to evaluate placental gas exchange capacity in pre-eclampsia and fetal growth restriction (FGR). STUDY DESIGN: Two nested case-control studies were conducted between: (i) pre-eclamptic appropriate-for-gestational-age fetus (AGA) and non-pre-eclamptic AGA; and (ii) pre-eclamptic FGR and non-pre-eclamptic FGR based on gestational age match. Umbilical A-V gas differences were compared between groups. RESULTS: Pre-eclamptic AGA was associated with smaller A-V pO(2) and A-V pCO(2) differences compared to non-pre-eclampsia (A-V pO(2), 7.1+/-3.8 mm Hg vs. 11.3+/-5.9 mm Hg, P=0.001; A-V pCO(2), 7.8+/-5.7 mm Hg vs. 10.7+/- 5.9 mm Hg, P=0.01). Pre-eclamptic FGR was associated with smaller A-V pO(2) and A-V pCO(2) differences compared to non-pre-eclampsia (A-V pO(2), 6.6+/-3.1 mm Hg vs. 10.8+/-8.1 mm Hg, P<0.001; 6.7+/-4.5 mm Hg vs. 10.9+/-10.3 mm Hg, P=0.044). Pre-eclamptic FGR also had significantly lower venous pO(2) but not arterial pO(2) (Venous pO(2), 20.3+/-6.3 mm Hg vs. 25.4+/-11.9 mm Hg, P=0.003). CONCLUSION: Pre-eclampsia decreases the placental oxygenation capacity as measured by the umbilical arterial-venous oxygen difference.

Umbilical arterial-venous blood gas difference: a novel expression of placental respiratory function.

We applied the concept of umbilical arterial and venous (A-V) blood gas difference in evaluating placental respiratory function to establish normative values for these relationships. Umbilical A-V cord blood gas samples were obtained in standardized fashion in uncomplicated singleton pregnancies. A-V pO (2) and A-V pCO (2) differences were related to obstetric factors, placental weight, and gestational age. Mean absolute differences in uncomplicated vaginal deliveries between umbilical artery and umbilical vein were: pO (2) 11.4 +/- 7.0 mm Hg and pCO (2) 11.9 +/- 6.8 mm Hg. Values in nonlabor cesarean section cases did not differ significantly from those of cases delivered vaginally. A-V pO (2) differences did not vary significantly across gestation (Pearson's R = 0.05, P = 0.43) and did not correlate with birth weight ( R = 0.06, P = 0.30). A-V pCO (2) differences showed increases with gestational age ( R = 0.15, P = 0.008) and with birth weight ( R = 0.18, P = 0.002). Results similar to those of women delivered vaginally were seen in nonlabor cesarean deliveries. Duration of labor did not impact the A-V blood gas relationship. Umbilical A-V oxygen differences reflect placental respiratory function independent of gestational age, birth weight, duration of labor, and mode of delivery. They are easy to collect and represent a potentially valuable resource for assessment of placental function.

The effect of computer-mediated administration on self-disclosure of problems on the addiction severity index.

OBJECTIVES: People tend to disclose more personal information when communication is mediated through the use of a computer. This study was conducted to examine the impact of this phenomenon on the way respondents answer questions during computer-mediated, self-administration of the Addiction Severity Index (ASI) called the Addiction Severity Index-Multimedia Version((R)) (ASI-MV((R))). METHODS: A sample of 142 clients in substance abuse treatment was administered the ASI via an interviewer and the computerized ASI-MV((R)), three to five days apart in a counterbalanced order. Seven composite scores were compared between the two test administrations using paired t-tests. Post hoc analyses examined interviewer effects. RESULTS: Comparisons of composite scores for each of the domains between the face-to-face administered and computer-mediated, self-administered ASI revealed that significantly greater problem severity was reported by clients in five of the seven domains during administration of the computer-mediated, self-administered version compared to the trained interviewer version. Item analyses identified certain items as responsible for significant differences, especially those asking clients to rate need for treatment. All items that were significantly different between the two modes of administration revealed greater problem severity reported on the ASI-MV((R)) as compared to the interview administered assessment. Post hoc analyses yielded significant interviewer effects on four of the five domains where differences were observed. CONCLUSIONS: These data support a growing literature documenting a tendency for respondents to be more self-disclosing in a computer-mediated format over a face-to-face interview. Differences in interviewer skill in establishing rapport may account for these observations.

Gravid hysterectomy: a decade of experience at an academic referral center.

OBJECTIVE: To evaluate the incidence of gravid hysterectomy (GH) and to examine the indications as well as risk factors and complications associated with the procedure at an academic perinatal referral center. STUDY DESIGN: Retrospective chart review of all patients who underwent GH from 1991 to 2001. Demographics, obstetric history, delivery information, complications and outcome were analyzed. RESULTS: There were 34 GHs out of 19,491 deliveries (1.74/1000). The preoperative indications were hemorrhage associated with atony (32.4%), placenta accreta (20.6%) and uncontrolled bleeding (17.6%). Of the patients, 87.5% were parous and 53.1% had previous cesarean section. GH was performed prior to viability in 3. GH followed cesarean delivery in 24 (68.6%). Uterine and/or hypogastric artery ligation were performed in 11 (32.4%). Postoperative complications included surgical re-exploration for recurrent hemorrhage in 5, transfusion of blood products in 30, disseminated intravascular coagulopathy in 15, prolonged (> 24 hours) ventilation in 10 and admission to the SICU for prolonged intensive care in 12. There were 2 maternal deaths (5.9%). A significant rise in GH rate from 1/800 to 1/299 occurred over the past 5 years despite constant cesarean rates (chi2, p < 0.05). CONCLUSION: Rates of GH increased over the period examined. Placenta accreta associated with previous cesarean section is the predominant risk factor for GH.

Protease inhibitor therapy and fetal growth potential in HIV-positive women.

Our objective was to test if protease inhibitors (PIs) increase the incidence of fetal growth restriction (FGR). Human immunodeficiency (HIV)-seropositive women were studied. At birth the neonatal weight percentile was assigned by predicted growth potential (GP), accounting for race, parity, weight, height, gestational age, birthweight, and gender (Gardosi, 1992). FGR was defined as GP < 10% percentile. Maternal age, CD4 count, viral load, weight gain, prenatal care, tobacco, alcohol, substance abuse, and PI use were related to FGR using chi-square and multiple regression analysis. Ninety-three of 191 women received PI. In these, FGR occurred in 27 (29%) compared with 15 (15.3%) in the non-PI group ( P = 0.02). Maternal CD4 count ( P < 0.0001) was the primary determinant, and smoking ( P = 0.037) was an independent cofactor for FGR (Nagelkerke r2 = 0.24). Twenty-six of 82 (31.7%) smokers had FGR, versus 16 of 109 (14.7%) of nonsmokers (odds ratio, 2.69; 95% confidence interval, 1.33 to 5.46; P = 0.005). After exclusion of the CD4 count, PI became a cofactor for FGR ( P = 0.021 and Nagelkerke r2 = 0.104). We concluded that maternal HIV status and smoking determine the risk for FGR. Although PIs increase the risk for FGR, this effect appears to depend on maternal disease severity.

Analysis of disease in the obstetric intensive care unit at a university referral center: a 24-month review of prospective data.

OBJECTIVE: To determine the current spectrum of disease in an obstetric population resulting in admission to the intensive care unit (ICU) at a tertiary care hospital. STUDY DESIGN: Analysis of data from obstetric patients admitted for critical care management at the University of Maryland Medical Center over a 24-month period. RESULTS: Critical care admission was required for 34 (1.3%) of 2,565 women admitted for deliveries; 38.5% of patients were delivered during their ICU admission. Preexisting medical conditions were present in 67.6% (76.5% were in the antenatal period vs. 23.5% in the postpartum period). Conditions leading to ICU admission included organ system failure, respiratory failure, central nervous system disease, cardiac failure, preeclampsia and postpartum hemorrhage. The median Acute Physiology and Chronic Health Evaluation II (APACHE II) score overall was 11.0 (antenatal 12.0, postpartum 10.5). Although the predicted maternal mortality rate was 12.9% (14.6% in the antenatal period and 12.1% in the postpartum period), the actual mortality rate was 0%. CONCLUSION: In this population, the antenatal period now accounts for the majority of ICU admissions. Respiratory failure (mainly from infectious etiologies) has surpassed obstetric hemorrhage as the primary reason for ICU admission. Finally, the APACHE II scoring system is inaccurate for use in an obstetric population.

Simulated laparoscopic operating room crisis: An approach to enhance the surgical team performance.

OBJECTIVE: Diminishing human error and improving patient outcomes is the goal of task training and simulation experience. The fundamentals of laparoscopic surgery (FLS) is a validated tool to assess technical laparoscopic skills. We hypothesize that performance in a crisis depends on technical skills and team performance. The aim of this study was to develop and validate a high-fidelity simulation model of a laparoscopic crisis scenario in a mock endosuite environment. METHODS: To establish the feasibility of the model as well as its face and construct validity, the scenario evaluated the performances of FLS-certified surgeon experts (n = 5) and non-FLS certified novices (n = 5) during a laparoscopic crisis scenario, in a mock endosuite, on a simulated abdomen. Likert scale questionnaires were used for validity assessments. Groups were compared using previously validated rating scales on technical and nontechnical performance. Objective outcome measures assessed were: time to diagnose bleeding (TD), time to inform the team to convert (TT), and time to conversion to open (TC). SAS software was used for statistical analysis. RESULTS: Median scores for face validity were 4.29, 4.43, 4.71 (maximum 5) for the FLS, non-FLS, and nursing groups, respectively, with an inter-rater reliability of 93%. Although no difference was observed in Veress needle safety and laparoscopic equipment set up, there was a significant difference between the two groups in their overall technical and nontechnical abilities (p < 0.05), specifically in identifying bleeding, controlling bleeding, team communication, and team skills. There was a trend towards a difference between the two groups for TD, TT, and TC. While experts controlled bleeding in a shorter time, they persisted longer laparoscopically. CONCLUSIONS: Our evidence suggests that face and construct validity are established for a laparoscopic crisis simulation in a mock endosuite. Technical and nontechnical performance discrimination is observed between novices and experts. This innovative multidisciplinary simulation aims at improving error/problem recognition and timely initiation of appropriate and safe responses by surgical teams.

Rupture of the uterine scar during term labour: contractility or biochemistry?

OBJECTIVE: Vaginal birth after a prior low transverse caesarean section (VBAC) is advocated as a safe and effective method to reduce the total caesarean section rate. However, the risk of uterine rupture has dampened the enthusiasm of practising clinicians for VBAC. Uterine rupture occurs more frequently in women receiving prostaglandins in preparation for the induction of labour. We hypothesised that similar to the cervix, prostaglandins induces biochemical changes in the uterine scar favouring dissolution, predisposing the uterus to rupture at the scar of the lower segment as opposed to elsewhere. DESIGN: We tested aspects of this hypothesis by investigating the location of uterine rupture associated with prostaglandins and compared it with the sites of rupture in the absence of prostaglandins. SETTINGS: Two North American University Hospitals. POPULATION: Twenty-six women with a prior caesarean section, experiencing uterine rupture in active labour. METHODS: Retrospective review of all pregnancies complicated by uterine rupture at two North American teaching hospitals from 1991 to 2000. MAIN OUTCOME MEASURE: Site of the uterine rupture. RESULTS: Thirty-four women experienced rupture after a previous caesarean section with low transverse uterine incision. Ten of the women who ruptured (29%) received prostaglandins for cervical ripening (dinoprostone: n= 8 or misoprostol: n= 2) followed by either spontaneous contractions (n= 3) or oxytocin augmentation during labour (n= 7). In 16 women (47%), oxytocin alone was sufficient for the induction/augmentation of labour. Eight (23%) women ruptured at term before reaching the active phase of labour in the absence of pro-contractile agents or attempted VBAC. There were no differences among the groups in terms of age, body mass index, parity, gestational age, fetal weight or umbilical cord pH measurements. Women treated with prostaglandins experienced rupture at the site of their old scar more frequently than women in the oxytocin-alone group whose rupture tended to occur remote from their old scar (prostaglandins 90%vs oxytocin 44%; OR: 11.6, 95% CI: 1.2-114.3). CONCLUSION: Women in active labour treated with prostaglandins for cervical ripening appear more likely to rupture at the site of their old scar than women augmented without prostaglandins. We propose that prostaglandins induce local, biochemical modifications that weaken the scar, predisposing it to rupture.

Intrauterine pressure during the second stage of labor in obese women.

OBJECTIVE: The perception that obese women have longer labors and a higher frequency of operative delivery because they are "poor pushers" persists despite the absence of objective study. We tested the hypothesis that obese women generate inadequate intrauterine pressure during the second stage of labor. METHODS: Intrauterine pressure was prospectively measured in 71 women during the second stage of labor. Obesity was defined as a body mass index (BMI) greater than 29 (n = 17). A BMI below 25 was normal (n = 40). Women with a BMI between 26 and 29 (n = 14) were considered overweight. All women labored with epidural analgesia and were alert and responsive throughout the study. After recording the baseline contractility, a standardized Valsalva maneuver was performed during contractions. The area under the intrauterine pressure curve (integral) was used as an estimate of uterine contractility. RESULTS: All women delivered vaginally. There were no significant differences in baseline uterine contractility among obese, overweight, and normal women either before (obese 1,787 mm Hg/s; 95% confidence interval [CI] 1,164, 2,742 versus normal 1,569 mm Hg/s; 95% CI 718, 2,371 versus overweight 1,770 mm Hg/s; 95% CI 1,305, 2,835; P =.223) or during Valsalva maneuver (obese 2,831 mm Hg/s; 95% CI 1,771, 4,599 versus normal 2,637 mm Hg/s; 95% CI 1,240, 4,390 versus overweight 2,813 mm Hg/s; 95% CI 1,209, 4,982; P =.742). A BMI greater than 25 was associated with a higher frequency of oxytocin augmentation (P =.037). Univariate analysis revealed a relationship between labor duration and BMI (r = 0.299, P =.018). Obese women labored longer during the active phase (one-way analysis of variance, P =.02), but second-stage duration was similar among groups (one-way analysis of variance P =.44). Obesity did not increase the incidence of perineal lacerations (P =.82) or frequency of operative delivery (relative risk obese versus nonobese = 0.212; 95% CI 0.04, 1.05). CONCLUSION: Obese women produce second-stage intrauterine pressures equivalent to women with a normal BMI, although they may require oxytocin augmentation more often. LEVEL OF EVIDENCE: II-2

Uterine contractility in women whose fetus is delivered in the occipitoposterior position.

OBJECTIVE: Most fetuses in the occipitoposterior position rotate spontaneously after striking the pelvic floor. The increased prevalence of prolonged labor, operative delivery, and oxytocin augmentation in women with an occipitoposterior fetal position seems consistent with decreased uterine contractility. We sought to test the hypothesis that women with a persistent occipitoposterior fetal position have inadequate intrauterine pressure. STUDY DESIGN: Intrauterine pressure was measured prospectively electronically in 94 women whose labor pain was controlled by patient-requested epidural analgesia. Eleven women (12%) were delivered as a persistent occipitoposterior fetal position. In a nested case-control study, these women were compared with 22 women who were delivered as an occipitoanterior fetal position who were matched for age, parity, gestational age, cervical examination at study enrollment, and body mass index. The intrauterine pressure measurements were initiated during the first stage of labor and continued throughout the entire labor process. Women were encouraged in the second stage of labor, after a period of recording baseline contractility, to push using a standardized Valsalva maneuver once the vertex reached the +2 station. The area under the intrauterine pressure curve (integral) was used to estimate uterine contractility and expulsive performances. RESULTS: Five women (45%) in the occipitoposterior group required operative delivery. The average duration of the second stage of labor in the occipitoposterior group was 91.4 +/- 23.2 minutes compared with 51.7 +/- 6.6 minutes in the occipitoanterior fetal position (P =.04). Ninety percent of women in the occipitoposterior group required oxytocin, compared with 59% of the women in the occipitoanterior group (P =.11). There were no differences in uterine contractility between occipitoposterior and occipitoanterior groups during either the first stage of labor (integral mean +/- SEM: occipitoposterior [1685.3 +/- 194.6 mm Hg. s] vs occipitoanterior fetal position [1700.8 +/- 128.9 mm Hg. s, P =.98]) or second stages of labor (occipitoposterior [1952.6 +/- 186.5 mm Hg. s] vs occipitoanterior fetal position [1740.8 +/- 104.3 mm Hg. s, P =.46]). Further, there were no significant differences in pushing performances between the occipitoposterior and occipitoanterior groups (Valsalva maneuver: occipitoposterior 2864.9 +/- 328.8 mm Hg. s] vs occipitoanterior [2898.6 +/- 222.2 mm Hg. s, P =.90]). CONCLUSION: Women who were delivered as a persistent occipitoposterior fetal position do not have lower intrauterine pressure levels immediately before or during the second stage of labor.

Myometrial thickness during human labor and immediately post partum.

OBJECTIVE: Morphologic studies suggest dramatic, asymmetric uterine growth during pregnancy that is caused by muscle cell hypertrophy. This growth is most marked at the fundus. Our objective was to evaluate sonographically the in vivo changes in myometrial thickness during active labor, second-stage labor, and after delivery. STUDY DESIGN: Abdominal ultrasound scans were performed on 52 term pregnant women to investigate the dynamic changes in myometrial thickness during the active and second stages of labor and immediately after delivery. Twenty-six women (mean +/- SEM gestational age, 39.09 +/- 0.3 weeks) were in active labor (cervical dilatation >4 cm with regular uterine contractions). An additional 26 nonlaboring women (gestational age, 39.8 +/- 0.2 weeks) provided control measurements. The myometrium was defined sonographically as the echo homogeneous layer between the serosa and the decidua. Myometrial thickness was measured at the low segment and mid anterior, fundal, and posterior uterine walls by the same observer. Myometrial thickness was also measured during uterine contractions and after artificial rupture of the amniotic membranes. All laboring women had uncomplicated labor patterns when studied and were delivered spontaneously. RESULTS: The myometrium was significantly thinner during active labor compared with nonlabor at each site studied: midanterior (mean [+/-SEM] myometrial thickness, 5.8 +/- 0.27 vs 8.83 +/- 0.51 mm; t test, P <.001), fundus (mean myometrial thickness, 6.78 +/- 0.32 vs 8.49 +/- 0.35 mm; P =.0015), and posterior (mean myometrial thickness, 6.22 +/- 0.34 vs 8.12 +/- 0.30 mm; P <.001). However, myometrial thickness did not differ among sites within the two groups. The thickness of the low segment was not affected by labor status (nonlabor, 4.68 +/- 0.48 vs labor, 4.66 +/- 0.37 mm; P =.97). Similarly, the myometrial thickness of the anterior uterine wall was unaffected by contractions (no contractions, 5.56 +/- 0.2 vs contractions, 5.68 +/- 0.22 mm; t test, P =.654). There was no change in myometrial thickness measured immediately before and after rupture of the amniotic membranes, despite a significant decrease of the amniotic fluid index. There was significant thickening of the anterior and fundal myometrium during the second stage of labor after the fetal head descended to +3 station by digital examination (anterior, 12.99 +/- 0.60 vs 5.8 +/- 0.27 mm; t test, P <.001; fundus, 10.61 +/- 1.63 vs 6.78 +/- 0.32 mm; t test, P =.04). Valsalva maneuver (pushing) during contractions did not affect myometrial thickness at the fundus (between contractions, 10.61 +/- 1.63 vs pushing, 10.76 +/- 1.95 mm; t test, P =.99). Immediately after delivery, the myometrial thickness at the placental insertion site was the thinnest. After completion of the third stage of labor, the uterine fundus remained significantly thinner than the anterior and posterior walls (fundus, 27.37 +/- 3.5 mm vs anterior, 40.94 +/- 3.5 vs posterior, 42.34 +/- 2.44; one-way analysis of variance, P =.02). CONCLUSION: There is significant and widespread thinning of the myometrium during active labor. Descent of the fetal head during the second stage of labor is associated with a significant relative thickening of the anterior and fundal myometrium. After delivery, the relationship reverses. These findings suggest the directionality of the expulsive force vectors (fundal dominance) is not determined by asymmetric myometrial growth but, rather, may be a function of increased "myometrial mass" that results from increased surface area at the fundus.

Effects of sublingual nitroglycerin on human uterine contractility during the active phase of labor.

Nitroglycerin is administered intravenously in acute obstetric emergencies to relax the uterus. However, complications (eg, hypotension, acute uterine bleeding) are frequent, which prompted a search for alternative routes of administration. We hypothesized that the sublingual administration of nitroglycerin would reduce uterine tone and contractility with few complications. Intrauterine pressure was measured in 12 women who were actively laboring (>4 cm dilatation, regular contractions) with epidural analgesia and who were alert and responsive throughout the study. In a double-blind fashion, subjects were randomized to receive either placebo or sublingual nitroglycerin (3 doses, 800 microg each) 10 minutes apart. The obstetric anesthesiologist continuously monitored maternal blood pressure and fetal heart rate. Cervical dilatation was assessed at the beginning and the end of the protocol. The area under the intrauterine pressure curve (integral) was used to estimate uterine contractility. Intrauterine pressure was analyzed before the randomization code was broken. Nitroglycerin did not alter the intrauterine pressure integral after the first dose (placebo, 3147 mm Hg x s [95% CI, 2206-4088] vs nitroglycerin, 4146 mm Hg x s [95% CI, 2451-5841]; P =.22), second dose (placebo, 3123 mm Hg x s [95% CI, 2447-3799] vs nitroglycerin, 3611 mm Hg x s [95% CI, 2723-4499]; P =.28), or third dose (placebo, 3303 mm Hg x s [95% CI, 2616-3990] vs nitroglycerin, 3810 mm Hg x s [95% CI, 2306-5314]; P =.45). Cervical dilation, basal uterine tone, duration and frequency of uterine contractions, or fetal heart rhythm remained unaffected. Maternal mean arterial pressure decreased significantly after nitroglycerin was administered. All women were delivered vaginally without intervention. Three doses of sublingual nitroglycerin (800 microg per dose) reduce neither uterine activity nor tone, despite lowering maternal blood pressure. If a clinical option, sublingual nitroglycerin will require a higher dose, which would place mother and fetus at risk for complication.