Correction of fetal umbilical vein flow imbalance following laser surgery for twin-twin transfusion syndrome.

OBJECTIVES: Twin-twin transfusion syndrome (TTTS) is characterized by unequal hemodynamics between the twins. We aimed to assess preoperatively the difference in umbilical vein flow (UVF) between the recipient and donor monochorionic diamniotic twins and evaluate the change in UVF following laser surgery in both twins. METHODS: This was a retrospective cohort study of differences in UVF that occurred following laser surgical treatment of TTTS. Sonographic assessment of the umbilical vein before and 24 h after fetoscopic laser surgery for TTTS was performed. Umbilical vein diameter and time-averaged maximum velocity were measured, and UVF per kg (UVF/kg) was converted into a Z-score by a calculator created using gestational age as an independent variable. Z-score values were converted into centiles, which were evaluated statistically. Median differences in UVF/kg centile values were adjusted for TTTS stage and presence of arterioarterial anastomoses. RESULTS: The study population consisted of 363 TTTS patients. The adjusted preoperative median difference in UVF/kg centile between the recipient vs donor twin was 17.9% (-17.1% to 57.6%), P < 0.0001. The adjusted median difference in UVF/kg centile between the postoperative vs preoperative period among recipients was 2.2% (-10.8% to 13.8%), P < 0.0001, while the adjusted median difference among donors was 27.3% (8.2%-34.6%), P < 0.0001. CONCLUSION: The preoperative difference in UVF between the recipient and donor twins confirms the pathophysiology of TTTS. Postoperatively, the substantial increase in UVF of the donor twin and the relatively small increase in UVF of the recipient twin confirm that ablation of the vascular communications resulted in rapid improvement in perfusion of the donor twin. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Role of low placental share in twin-twin transfusion syndrome complicated by intrauterine growth restriction.

OBJECTIVES: Prior studies have demonstrated that donor twin survival following treatment of twin-twin transfusion syndrome (TTTS) was highly associated with donor intrauterine growth restriction (IUGR). Here, we hypothesized that donor IUGR may be attributed in part to low placental share. STUDY DESIGN: The study population consisted of all patients who underwent laser treatment for TTTS at a single institution between 2006-2010. Only those pregnancies with dual survival at birth were included so that placental share information could be interpreted. We examined the relationships between Quintero Stage (with separate analysis of Stage III patients with critically abnormal donor Doppler findings) and low placental share (defined as ≤ 30%) with IUGR (<10th percentile) using chi-square analysis and multivariable logistic regression modeling. RESULTS: Of 210 patients treated, 159 (75.7%) had dual survivors at birth. Of these, placental share was documented in 90 cases (56.6%). Twenty-seven (30.0%) had low placental share, and 37 (41.1%) had IUGR. IUGR was associated with low placental share (63.0% vs. 31.7%, P = 0.0116). IUGR was also associated with Stage III patients (57.4% vs. 23.3%, P = 0.0021), and in particular with Stage III patients with donor involvement (77.8% vs. 25.4%, P < 0.0001). In logistic regression modeling, both low placental share and Stage III with donor involvement were independent risk factors for IUGR (OR = 3.5 [1.2-10.3], P = 0.0206, and OR = 10.1 [3.3-30.6], P < 0.0001, respectively). CONCLUSIONS: Donor IUGR in TTTS pregnancies appears to be associated, in part, with low placental share.

Pre-pregnancy weight and excess weight gain are risk factors for macrosomia in women with gestational diabetes.

OBJECTIVE: To determine whether women with gestational diabetes mellitus (GDM) whose weight gain exceeded the 2009 Institute of Medicine (IOM) recommendations were more likely to have macrosomia. STUDY DESIGN: Retrospective cohort study of the association of weight gain in women with Class A1 GDM, with term (≥37 weeks) singleton liveborns and macrosomia (birthweight ≥4000 g). Multivariate logistic regression models were used to adjust for covariates and test for interactions. RESULT: Of 1502 women studied, pre-pregnancy body mass index (BMI) categories were: normal (39.6%), overweight (28.5%) and obese (31.9%). The mean (±standard deviation ) weight gain (lbs) for these groups was: 27.6±10.9, 24.2±13.0 and 18.8±16.3 (P<0.0001), whereas the occurrence of macrosomia was 7.4, 11.4 and 19.0%, respectively. Women with an obese BMI were twice as likely to have a macrosomic infant compared with women in the normal BMI group (odds ratio, OR 2.0; 95% CI 1.4-3.0; P=0.0005). Independently, women who exceeded the IOM guidelines were three times more likely to have a macrosomic infant (OR 3.0, 95% CI 2.2-4.2, P<0.0001). CONCLUSION: Maternal pre-pregnancy weight and weight gain during pregnancy appear to be significant and independent risk factors for macrosomia in women with GDM.

Fetal middle cerebral artery Doppler fluctuations after laser surgery for twin-twin transfusion syndrome.

OBJECTIVE: The objective of this study was to compare alterations in the middle cerebral artery (MCA) pulsatility index (PI) and mean velocity (V (mean)) after laser surgery for twin-twin transfusion syndrome (TTTS). STUDY DESIGN: MCA Doppler studies were conducted 1 day before and after laser surgery for TTTS. The pre- and postoperative mean (standard deviation) of the MCA PI and V (mean) z-scores of the recipient and donor fetuses were calculated and compared. Data were analyzed using paired testing and multivariable linear regression models. RESULTS: A total of 103 patients met the study criteria. Recipients' MCA PI increased from -1.29 (1.20) preoperatively to 0.14 (1.52) postoperatively (P < 0.0001), whereas the donors' PI did not change significantly (-0.31 (1.67) to -0.67 (1.29); P = 0.12). There was no significant difference between preoperative and postoperative MCA V (mean) in donors (0.39 (0.83) and 0.38 (0.93), respectively; P = 0.5048) or recipients (0.60 (0.74) and 0.63 (0.90), respectively; P = 0.5324). CONCLUSIONS: Despite the changes in the MCA PI after laser surgery for TTTS, the MCA V (mean) remained constant. These findings may suggest some autoregulatory capacity in the cerebral vessels of the mid-trimester fetus.

Health-related quality of life in women with nausea and vomiting of pregnancy: the importance of psychosocial context.

OBJECTIVE: To test whether women with hyperemesis gravidarum (HG) demonstrated lower health-related quality of life (HRQoL) scores compared with those with nausea and vomiting of pregnancy (NVP). STUDY DESIGN: Women with HG or NVP were examined during the first trimester. Multivariate models identified characteristics of women at risk for low HRQoL, as measured by an NVP-specific HRQoL test and a generic HRQoL test, the Short Form (SF)-36. RESULT: Although the SF-36 assessment did not discriminate between the two groups, the NVP-specific test showed that women with HG (N=29) were 3-6 times more likely than women with NVP (N=48) to have low HRQoL. Both tests demonstrated that perceived physical symptoms and multiple psychosocial factors, such as depression and marital status, seemed to be equally or more important than having HG. CONCLUSION: Although a low HRQoL was associated with an HG diagnosis, multiple physical symptoms and psychosocial factors placed both groups of women at risk.

Quantitative EEG in babies at risk for hypoxic ischemic encephalopathy after perinatal asphyxia.

OBJECTIVE: To evaluate an electroencephalography (EEG)-based index, the Cerebral Health Index in babies (CHI/b), for identification of neonates with high Sarnat scores and abnormal EEG as markers of hypoxic ischemic encephalopathy (HIE) after perinatal asphyxia. STUDY DESIGN: This is a retrospective study using 30 min of EEG data collected from 20 term neonates with HIE and 20 neurologically normal neonates. The HIE diagnosis was made on clinical grounds based on history and examination findings. The maximum-modified clinical Sarnat score was used to grade HIE severity within 72 h of life. All neonates underwent 2-channel bedside EEG monitoring. A trained electroencephalographer blinded to clinical data visually classified each EEG as normal, mild or severely abnormal. The CHI/b was trained using data from Channel 1 and tested on Channel 2. RESULT: The CHI/b distinguished among HIE and controls (P<0.02) and among the three visually interpreted EEG categories (P<0.0002). It showed a sensitivity of 82.4% and specificity of 100% in detecting high grades of neonatal encephalopathy (Sarnat 2 and 3), with an area under the receiver operator characteristic (ROC) curve of 0.912. CHI/b also identified differences between normal vs mildly abnormal (P<0.005), mild vs severely abnormal (P<0.01) and normal vs severe (P<0.002) EEG groups. An ROC curve analysis showed that the optimal ability of CHI/b to discriminate poor outcome was 89.7% (sensitivity: 87.5%; specificity: 82.4%). CONCLUSION: The CHI/b identified neonates with high Sarnat scores and abnormal EEG. These results support its potential as an objective indicator of neurological injury in infants with HIE.

Fetal heart rate changes associated with sequential selective laser surgery for twin-twin transfusion syndrome.

OBJECTIVE: To investigate perioperative changes in fetal heart rate (FHR) associated with sequential vs standard selective laser photocoagulation of communicating vessels for the treatment of twin-twin transfusion syndrome (TTTS). STUDY DESIGN: Women with TTTS were treated with the intent of using the sequential procedure. Those who failed this treatment were categorized as having undergone the standard procedure. Pre- and postoperative FHR of donor and recipient fetuses were analyzed. RESULT: Of 98 women, 35 received the standard technique. A postoperative drop in the mean donor FHR was observed in gestations receiving the standard laser, but not in those receiving the sequential technique. In multivariable models that included operative and gestational characteristics, the use of the sequential treatment was associated with improved stability of the FHR of the donor twin. CONCLUSION: The stability in donor FHR following sequential laser ablation when compared with the standard technique is consistent with improved donor hemodynamics.

Identifying women most likely to benefit from prevention strategies for postpartum hemorrhage.

OBJECTIVE: To identify women who are most likely to benefit from primary prevention strategies for postpartum hemorrhage (PPH). STUDY DESIGN: In a retrospective patient cohort, we applied recursive partitioning algorithms to identify the most discriminant risk factors and their interactions, and calculated the 'number needed to treat' to prevent a single case of PPH (estimated blood loss >1000 ml). RESULT: By delivery category, the highest risk groups with 'number needed to treat' ranging from 4 to 7 were: (1) vaginal delivery (PPH=0.7% of 16 218)-macrosomia with gestational diabetes and manual removal of the placenta; (2) primary cesarean (PPH=18.7% of 2696)-macrosomia and multiparity; and (3) repeat cesarean (PPH=16.0% of 1832)-uterine incision other than low transverse and failed vaginal birth after cesarean. CONCLUSION: Clinical profiles that identify women at risk for PPH can provide a foundation for the development of primary prevention strategies.

The psychosocial burden of hyperemesis gravidarum.

OBJECTIVE: To describe the psychosocial burden of hyperemesis gravidarum (HG) in a large cohort of affected women, focusing on previously unreported problems. STUDY DESIGN: Women with HG described their pregnancy history in an open-ended survey administered internationally through an HG website during 2003 to 2005. RESULT: Of the 808 participants, 626 (77.5%) were American. A large majority (82.8%) reported that HG caused negative psychosocial changes, consisting of (1) socioeconomic changes, for example, job loss or difficulties, (2) attitude changes including fear regarding future pregnancies and (3) psychiatric sequelae, for example, feelings of depression and anxiety, which for some continued postpartum. Women who reported that their health-care provider was uncaring or unaware of the severity of their symptoms were nearly twice as likely to report these psychiatric sequelae (odds ratio 1.86, 95% confidence interval 1.06 to 3.29, P=0.032). CONCLUSION: Over 80% of a large cohort of women with HG reported that HG caused a negative psychosocial impact.

Variation in elective primary cesarean delivery by patient and hospital factors.

OBJECTIVE: Our purpose was to describe variation in elective primary cesarean rates by nonclinical factors. STUDY DESIGN: With use of California discharge data and American Hospital Association data for 1995, patients were classified into 13 mutually exclusive categories for elective primary cesarean delivery. With use of recursive partitioning algorithms, women in each category were then studied to determine whether nonclinical factors were associated with elective primary cesarean delivery. RESULTS: A total of 463,196 women were delivered at 288 hospitals, and the elective primary cesarean delivery rate was 4.25% (19,664/463,196). Risk for elective primary cesarean delivery varied by clinical condition. The most discriminant risk factors were hospital type (malpresentation, multiple gestation, macrosomia, other hypertension), maternal age (antepartum bleeding, uterine scar, soft tissue disorder, preterm, unspecified), and teaching status (herpes, severe hypertension, unengaged head). CONCLUSION: This article presents methods that use administrative data to isolate and monitor the impact of nonclinical factors on the use of elective primary cesarean.

Variation in vaginal breech delivery rates by hospital type.

OBJECTIVE: To relate vaginal breech delivery rates to the following hospital types: public, health maintenance organization, private teaching, or private nonteaching. METHODS: In a retrospective study using administrative discharge data from Los Angeles County, California, we calculated the vaginal breech delivery rates of singleton breech deliveries during calendar years 1988 and 1991. RESULTS: Ten thousand four hundred breech deliveries were identified, 8988 (86.4%) term and 1412 (13.6%) preterm. Twelve percent (1252 of 10,400) were vaginal deliveries (10.1% term and 24.5% preterm). Term vaginal breech deliveries varied by hospital type and were more frequent in public hospitals (28.4%, 95% confidence interval [CI] 26.1%, 30.7%) and less frequent in private nonteaching hospitals (5.4%, 95% CI 4.8%, 5.9%). Term vaginal deliveries were 2.4 to 11.3 times more likely among black women and 1.3 to 6.3 times more likely for Hispanic women across all hospital types, compared with white women in private nonteaching hospitals. There was no difference in the proportion of preterm vaginal breech deliveries by hospital type (mean 24.5%). However, with the exception of public hospitals, the proportion of vaginal breech deliveries for both term and preterm deliveries varied significantly by ethnicity. CONCLUSION: The use of vaginal breech delivery varied by hospital type and patient ethnicity. Within private teaching and nonteaching hospitals, vaginal breech delivery was more likely for black women than for women of other ethnic groups. Further study is needed to understand the hospital policies or organizational factors, as well as the patient-related sociocultural and clinical factors, that contribute to those differences.

The significance of atypical glandular cells on routine cervical cytologic testing in a community-based population.

OBJECTIVES: We sought to determine the follow-up rate of women with glandular atypia on routine Papanicolaou smears in a community-based population and to describe the associated pathologic findings. STUDY DESIGN: Over a 12-month period, all patients with Papanicolaou smears with atypical glandular cells of undetermined significance were reviewed for demographic and clinical characteristics and followed up for a period of 12 to 24 months. RESULTS: Of the 48,890 Papanicolaou smears examined, 141 (0.29%) were diagnosed with atypical glandular cells of undetermined significance. Of these, 22 (17.6%) had no record of any subsequent investigation, and only 64 (51.2%) were monitored with both colposcopy and biopsy. Of the 64 biopsy specimens, 39 (60.9%) were positive for disease. Twenty-six (66.7%) were of squamous origin, with the most advanced lesion being cervical intraepithelial neoplasia 3. An additional patient had a combined cervical intraepithelial neoplasia and adenocarcinoma in situ lesion. Four (10.3%) additional patients had glandular cervical lesions, 2 benign polyps and 2 adenocarcinoma in situ lesions. Seven (17.9%) patients had endometrial lesions (benign polyps, 2 patients; complex atypical endometrial hyperplasia, 1 patient; and endometrial carcinoma, 4 patients). One patient had ovarian cystadenocarcinoma. Postmenopausal women were 5 times more likely to have a glandular lesion. Women with abnormal vaginal bleeding were also more likely to have a glandular lesion. These same patient groups were also more likely to have endometrial disease. CONCLUSION: The incidence of atypical glandular cells of undetermined significance on Papanicolaou smears in this community-based population was 0.29%, which is consistent with estimates from institution-based populations. Nearly 50% of women studied were not followed up with tissue biopsy. Of those with a tissue biopsy, 61% had positive findings, including 5 with cancer. Although postmenopausal status and abnormal vaginal bleeding were associated with endometrial or glandular disease, studies of larger patient populations should be conducted to examine potential risk factors for these conditions.

Vaginal birth after cesarean and uterine rupture rates in California.

OBJECTIVE: To describe attempted and successful vaginal birth after cesarean (VBAC) rates and uterine rupture rates for women with and without prior cesareans, and compare delivery outcomes in hospitals with different attempted VBAC rates. METHODS: We used California hospital discharge summary data for 1995 to calculate attempted and successful VBAC rates and uterine rupture rates. We used multivariate logistic regression models to evaluate and adjust for age, ethnicity, and payment source. We report the relative risk (RR), attributable fraction, and 95% confidence intervals (CIs) for uterine rupture. RESULTS: There were 536,785 delivery discharges during 1995. The cesarean rate was 20.8%, and 12.5% of women had histories of cesareans. Of women with histories of cesareans, 61.4% attempted VBAC and 34.8% were successful. There were 392 uterine ruptures (0.07%). Women with prior cesareans were 16.98 (95% CI 13.51, 21.43) times more likely to experience uterine rupture, attributable fraction 66% (95% CI 60%, 73%). Among women with prior cesareans, those who attempted VBAC were 1.88 (95% CI 1.45, 2.44) times as likely to have uterine rupture, attributable fraction 34% (95% CI 21%, 46%). Women who delivered in hospitals with high attempted VBAC rates were less likely to have cesarean deliveries, more likely to have successful VBACs, and more likely to experience uterine ruptures. CONCLUSION: Uterine rupture occurs at a low rate in women with and without prior cesarean delivery. Risk of rupture is increased among women with prior cesarean delivery and among those who attempt VBAC.

Neonatal platelet counts in fetal brain injury.

UNLABELLED: The objective of this study was to determine whether neonatal platelet counts can be used in fetal brain injury. The initial platelet counts, expressed as 1000 per mm3, of singleton term infants with and without permanent asphyxial brain injury were compared. Neonates with encephalopathy were divided into 3 groups: I--nonreactive fetal heart rate (FHR) pattern from admission until delivery; II--reactive FHR pattern on admission followed by nonreactivity, tachycardia, a loss of variability and repetitive FHR decelerations; and III--acute: reactive FHR pattern followed by a sudden prolonged FHR deceleration that lasted until delivery. The neonates and platelet counts for each group were as follows: CONTROL: 104 neonates, mean 281 +/- 56, range 154 to 411; I: 60, mean 185 +/- 80, range 28 to 365; II: 34, mean 251 +/- 66, range 100 to 375; and III: 35, mean 267 +/- 93, range 86 to 569. Platelet counts were significantly lower in neonates with encephalopathy (p <0.001). Group I differed statistically from both Groups II and III (p <0.001). These data suggest an association between the FHR pattern, fetal asphyxial brain injury, and the initial platelet count in singleton term neonates. Further investigation should be pursued to clarify the physiological processes leading to this result.

Acute fetal asphyxia and permanent brain injury: a retrospective analysis of current indicators.

OBJECTIVE: To determine whether a term neonate who has had sufficient intrapartum asphyxia to produce persistent brain injury will manifest the following four criteria: profound acidemia (arterial pH <7.00), an APGAR score < or =3 for 5 min or longer, seizures within 24 h of birth, and multiorgan system dysfunction. METHODS: Singleton, liveborn, neurologically impaired neonates > or =37 weeks gestation who lived at least 6 days and had sufficient documentation of current intrapartum asphyxia criteria were retrospectively analyzed. Of these infants, solely neonates with acute fetal asphyxia due to a sudden prolonged FHR deceleration that lasted until delivery from a catastrophic event, e.g., uterine rupture, cord prolapse, were included. Organ system dysfunction was defined by separate criteria for each organ system. Dysfunction in one or more was defined as multiorgan system dysfunction. RESULTS: Of the 292 eligible infants in the registry, 47 satisfied the entry criteria. In these 47 neonates, 10 (21%) satisfied all 4 criteria for intrapartum asphyxia. CONCLUSIONS: Our retrospective study suggests that currently used indicators to define permanent fetal brain injury are not valid.

Corticotrophin-releasing hormone and CRH-binding protein. Differences between patients at risk for preterm birth and hypertension.

BACKGROUND: During pregnancy in the second and third trimester there is a progressive rise in plasma CRH thought to be secreted by the placenta. Plasma CRH-BP inactivates CRH, which may prevent its peripheral action on the maternal pituitary and myometrium. In the last few weeks of pregnancy CRH-BP decreases, thereby causing an increase in free CRH or a CRH/CRH-BP complex available to play a role in the onset of parturition. OBJECTIVE: We tested the hypothesis that differences in CRH, CRH-BP, or a CRH/CRH-BP complex in patients at risk for preterm birth (PTB) and hypertension (HYP) account for the differences in the timing of parturition. METHODS: From a Behavior in Pregnancy Study database, we identified 18 patients who had spontaneous PTB and 23 patients who developed HYP. Both groups were case controlled and matched with patients who delivered at term (Normal). Maternal plasma samples had been appropriately collected from these patients at 18-20, 28-30, and 35-36 weeks gestational age. CRH levels were measured by double antibody RIA kit and the CRH-BP by a immunoradiometric technique. A CRH-BP/CRH dimer complex index was calculated. Statistical analysis was done using Kruskal-Wallis test for two cases. RESULTS: Maternal CRH (pg/ml) in the PTB cases compared to the HYP cases was significantly elevated at all three time periods. Maternal CRH-BP (pg/ml) in the PTB versus HYP cases was significantly lower at all three time periods in the PTB cases compared to the HYP cases. Maternal CRH-BP/CRH dimer complex index was significantly lower in the PTB cases at all three time periods than either the controls or the HYP cases, suggesting excessive CRH. The mean GA at delivery for the PTB cases was significantly lower than the control or HYP cases. CONCLUSIONS: These results suggest that those patients at risk for PTB have significantly elevated CRH, lower CRH-BP, and a reduced CRH-BP/CRH dimer complex index at all three time periods of assessment.

Does the onset of neonatal seizures correlate with the timing of fetal neurologic injury?

The onset of seizures after birth has been considered evidence of an intrapartum asphyxial event. The present study was undertaken to determine whether the timing of neonatal seizures after birth correlated with the timing of a fetal asphyxial event. Thus, singleton term infants diagnosed with hypoxic ischemic encephalopathy and permanent brain injury had a mean birth to seizure onset interval of 9.8 +/- 17.7 (range 1-90) hours. When these infants were categorized according to their fetal heart rate (FHR) patterns, the acute group (normal FHR followed by a sudden prolonged FHR deceleration that continued until delivery) tended to have earlier seizures than infants did within the tachycardia group (normal FHR followed by tachycardia, repetitive decelerations, and diminished variability) and the preadmission group (persistent nonreactive FHR pattern intrapartum). These seizure intervals were as follows: acute, 6.6 +/- 18.0 (range 1-90) hours; tachycardia, 11.1 +/- 17.1 (range 1-61) hours; and preadmission, 11.8 +/- 17.9 (range 1-79) hours (p < 0.05). But the range varied widely and no group was categorically distinct. In conclusion, the onset of neonatal seizures after birth does not, in and of itself, appear to be a reliable indicator of the timing of fetal neurologic injury.

The isolated choroid plexus cyst.

OBJECTIVE: To describe the karyotypes of a population of fetuses with choroid plexus cysts and compare affected fetuses with and without additional ultrasonographic findings. METHODS: The study population included all patients undergoing second-trimester ultrasound examination in a prenatal diagnostic program between January 1993 and October 1995. The records of all cases in which a choroid plexus cyst was found were reviewed, and information was abstracted regarding the fetal karyotype and the presence of other sonographic abnormalities. RESULTS: Two hundred ten cases of choroid plexus cysts were identified among 7617 patients (2.8%) who underwent second-trimester ultrasound examination. The majority of the cases (181, or 86%) involved isolated choroid plexus cysts and the remaining 29 (14%) were associated with additional ultrasonographic findings. Autosomal aneuploidy was found in one patient with an isolated choroid plexus cyst (trisomy 21) and in another with additional findings (trisomy 18); the mothers of both of these patients were at least 35 years old. For those fetuses with known outcome, the risk of aneuploidy with isolated choroid plexus cyst (one in 180) was not statistically significantly different from that associated with choroid plexus cyst accompanied by other sonographic findings (one in 26). More than 1000 fetuses with choroid plexus cysts would have to be studied to determine whether such a difference was real. CONCLUSION: Because of the rarity of aneuploidy, the reported risk for a fetus with an isolated choroid plexus cyst must be interpreted cautiously and should include the baseline risk.

Uterine activity patterns in uterine rupture: a case-control study.

OBJECTIVE: To determine whether uterine activity patterns are associated with intrapartum uterine rupture. METHODS: Because of the infrequency of uterine rupture, a case-control design was implemented. Cases were women who sustained uterine ruptures during a trial of labor, resulting in a neurologically impaired neonate. Controls were women who had a successful vaginal birth after cesarean (VBAC) or vaginal delivery with no history of uterine scar. The uterine activity patterns of cases were compared with those of each control group for number of contractions per hour, uterine tetany (contraction longer than 90 seconds), and uterine hyperstimulation (five or more contractions in a 10-minute period). RESULTS: The final study population consisted of 18 rupture patients, 35 VBAC patients, and 33 spontaneous vaginal delivery patients. Women in the rupture group had fewer contractions per hour (15.8+/-7.3) than VBAC (19.7+/-5.5) (P < .05) or spontaneous delivery group (19.4+/-6.6) (P < .10). VBAC patients were five times as likely to have 16 or more contractions per hour than were rupture patients, 95% confidence interval [CI] 1.3, 21.3, P < .02). Patients who had spontaneous delivery were 3.5 times more likely to have 16 or more contractions per hour than were rupture patients (95% CI 0.9, 14.1, P = .08). The rupture group had equal or less uterine tetany than did the controls. CONCLUSION: Uterine activity patterns and oxytocin use do not appear to be associated with the occurrence of intrapartum uterine rupture.