Nicholas Behrendt

The rate of cervical change and the phenotype of spontaneous preterm birth

OBJECTIVE Preterm birth is classified by the presence of uterine contractions and/or amniorrhexis at clinical presentation. This classification does not include prior cervical change. We hypothesized that the rate of cervical shortening before preterm birth would not differ according to clinical presentation. STUDY DESIGN We analyzed data from a completed study of paired cervical ultrasound measurements to test our hypothesis. Cervical ultrasound measurements obtained 4 weeks apart in the second trimester were related to gestational age and clinical presentation at birth. RESULTS Of 2521 eligible women, 128 were delivered after preterm labor and 106 after preterm membrane rupture; 89 delivered preterm for a medical or obstetrical indication; 2198 delivered at term. The rate of change was similar in women who presented with preterm labor (-0.96 mm/week) and preterm ruptured membranes (-0.82 mm/week). CONCLUSION Cervical shortening occurs at the same rate before spontaneous preterm birth, regardless of presentation.

Rate of Change in Cervical Length in Women With Vaginal Bleeding During Pregnancy

OBJECTIVE: To evaluate whether women with known risk factors for preterm birth will manifest different rates of cervical shortening preceding a spontaneous preterm birth. METHODS: We conducted a secondary analysis of data from the Maternal--Fetal Medicine Units Network Preterm Prediction Study. Known risk factors for preterm birth were recorded. Cervical lengths were measured between 22+0 weeks and 24+6 weeks, and again 4 weeks later. Cervical slope was defined as the change in cervical length between these visits divided by time (millimeters per week). Preterm birth was defined as preterm premature rupture of membranes or spontaneous preterm labor leading to delivery before 37 weeks of gestation. We analyzed the data for 2,584 women using logistic regression and tested for interaction between risk factors in the model to determine whether cervical shortening preceded preterm births in all variable groups. RESULTS: Cervical slope was not significantly associated with preterm birth (P=.9) in women with vaginal bleeding. Cervical slope was significantly associated with preterm birth in women without a history of vaginal bleeding (odds ratio 1.2, 95% confidence interval 1.1–1.4). CONCLUSIONS: Pregnancies without vaginal bleeding have a 20% increase in the risk of preterm birth for each additional millimeter per week increase in cervical slope. Pregnancies with vaginal bleeding are at risk for preterm birth but do not appear to undergo progressive cervical shortening. This suggests that women with vaginal bleeding undergo a different mechanism leading to preterm birth. LEVEL OF EVIDENCE: II

Twin-twin transfusion and laser therapy.

Purpose of review Twin-to-twin transfusion syndrome (TTTS) is an uncommon, but dangerous, complication of monochorionic diamniotic twin gestations. The purpose of this review is to provide an update on the evolving treatments in TTTS as it pertains primarily to laser photocoagulation, as well as to provide recently published information on outcomes. Recent findings The Solomon laser technique, in which selective fetoscopic laser photocoagulation is first performed and then followed by laser of the vascular equator from one side of the placenta to the other, reduces TTTS complications of twin anemia–polycythemia syndrome and recurrent TTTS. The addition of fetal echocardiography to the historical staging of TTTS adds important information that may guide future therapies. The postlaser ablation rate of neurodevelopmental delay in TTTS has recently been reported to be 14%. Cotwin demise is a significant complication of untreated TTTS and survival carries a 25% risk of cystic periventricular leukomalacia, middle cerebral artery infarction, and injury to other central nervous system structures as noted by neuroimaging. Summary Laser therapy for TTTS is clearly the only therapy that halts the disease process, allows both fetuses an opportunity to survive and protects a surviving cotwin in the event of the demise of one twin. Laser techniques have evolved greatly over the last 25 years and recent reports with the addition of the Solomon technique appearing to reduce some postlaser complications (twin anemia–polycythemia sequence and recurrent TTTS). Future focus of TTTS therapy should be centered on understanding the pathophysiology of the disease better with improvement in staging of the disease and on comparison of different laser techniques with the overall goal of not only increasing twin survival rates but also reducing long term neurodevelopmental morbidity.

Ultrasound versus MRI: is there a difference in measurements of the fetal lateral ventricles?

Abstract Objective: To evaluate whether fetal brain lateral ventricle measurements differ between ultrasound (US) and MRI. Methods: We evaluated 115 fetuses with US and MRI performed within 24 h of each other. Ventricular measurements were performed in the axial plane at the level of the atria for both modalities and the right and left ventricles were evaluated separately. We compared mean measurements; mean differences, association with gestational age (GA), association with the presence of a brain anomaly, and agreement between MRI and US. Results: The LV and RV were measured in 65 and 64 cases, respectively. LV and RV size estimates were significantly greater when measured by MRI compared with US (p < 0.001). Therefore, LV and RV were 0.87 mm and 0.89 mm larger in MRI versus US, respectively. Neither GA at measurement or presence/absence of a brain anomaly was significantly associated with differences in measurements. When comparing the agreement between the US and MRI measurements for ventriculomegaly; the kappa level of agreement for the LV and RV was 0.74 for each. Conclusion: MRI measurements of ventricles are significantly larger than the measurements by US by ∼1 mm. There is a good level of agreement when categorizing by normal, mild and severe ventriculomegaly.

Indomethacin Dosing and Constriction of the Ductus Arteriosus During Open Fetal Surgery for Myelomeningocele Repair

Introduction: The use of perioperative tocolytic agents in fetal surgery is imperative to prevent preterm labor. Indomethacin, a well-known tocolytic agent, can cause ductus arteriosus (DA) constriction. We sought to determine whether a relationship exists between preoperative indomethacin dosing and fetal DA constriction. Materials and Methods: This is an IRB-approved, single-center retrospective observational case series of 42 pregnant mothers who underwent open fetal myelomeningocele repair. Preoperatively, mothers received either 1 (QD) or 2 (BID) indomethacin doses. Maternal anesthetic drug exposures and fetal cardiac dysfunction measures were collected from surgical and anesthesia records and intraoperative fetal echocardiography. Pulsatility Index was used to calculate DA constriction severity. Comparative testing between groups was performed using t- and chi-square testing. Results: DA constriction was observed in all fetuses receiving BID indomethacin and in 71.4% of those receiving QD dosing (p = 0.0002). Severe DA constriction was observed only in the BID group (35.7%). QD indomethacin group received more intraoperative magnesium sulfate (p < 0.0001). Minimal fetal cardiac dysfunction (9.5%) and bradycardia (9.5%) were observed in all groups independent of indomethacin dosing. Conclusions: DA constriction was the most frequent and severe in the BID indomethacin group. QD indomethacin and greater magnesium sulfate dosing was associated with reduced DA constriction.

Modified Hysterotomy Closure Technique for Open Fetal Surgery

Objective: We reviewed our experience with open fetal surgical myelomeningocele repair to assess the efficacy of a new modification of the hysterotomy closure technique regarding hysterotomy complication rates at the time of cesarean delivery. Methods: A modification of the standard hysterotomy closure was performed on all patients undergoing prenatal myelomeningocele repair. The closure consisted of an interrupted full-thickness #0 polydioxanone (PDS) retention suture as well as a running #0 PDS suture to re-approximate the myometrial edges, and the modification was a third imbricating layer resulting in serosal-to-serosal apposition. A standard omental patch was placed per our routine. Both operative reports and verbal descriptions of hysterotomy from delivering obstetricians were reviewed. Results: A total of 49 patients underwent prenatal repair of myelomeningocele, 43 having adequate follow-up for evaluation. Of those, 95.4% had completely intact hysterotomy closures, with only 1 partial dehiscence (2.3%) and 1 thinned scar (2.3%). There were no instances of uterine rupture. Discussion: In patients undergoing this modified hysterotomy closure technique, a much lower than expected complication rate was observed. This simple modified closure technique may improve hysterotomy healing and reduce obstetric morbidity.

Case report of myometrial window following fetoscopic treatment of twin-twin transfusion syndrome: indications of underlying collagen vascular disease?

Intraperitoneal amniotic fluid leak is a known complication of fetoscopic procedures that usually resolves spontaneously with expectant management. Intraperitoneal amniotic fluid leak may persist after fetoscopic procedures due to a myometrial window as well as to persistent chorioamniotic membrane disruption, which may be amenable to surgical repair.

Influence of maternal body mass index and gestational age on accuracy of first trimester gender assignment

Objective. To determine the influence of maternal body mass index (BMI) and gestational age on the accuracy of image acquisition, first trimester fetal gender determination, and correct assignment. Methods. Women presenting for first trimester aneuploidy risk assessment at 110 to 136 weeks were prospectively enrolled. A mid-sagittal view of the fetus including the genital tubercle was obtained. The angle of the genital tubercle was measured with male assigned for angle >30°, female <10°, and indeterminate if 10–30°. This was compared with gender at birth. The influence of maternal and pregnancy characteristics on both image acquisition and correct gender assignment were evaluated. Results. A total of 256 women with 260 fetuses undergoing first trimester risk assessment were enrolled. The genital tubercle was identified in 247/260 (95%) of cases. Image acquisition was negatively influenced by increasing maternal BMI and early gestational age (34.8 ± 7.7 vs. 27.0 ± 6.1 kg/m2, p < 0.0001 and 12.3 ± 0.5 vs. 12.6 ± 0.5 weeks, p = 0.02). Gender was assigned in 93.1% and correctly matched in 85.8% of fetuses. Positive predictive value (PPV) for male and female fetuses were 88.9% and 79.8%, respectively. Correct gender assignment was more likely in male compared with female fetuses (91.4 vs. 80.5%, p = 0.02). Conclusion. Increasing maternal BMI negatively influences image acquisition during the first trimester for gender determination, but does not decrease the accuracy of correct gender assignment if the image is obtained.