Lysophosphatidylcholine acyltransferase 1 protein is present in maternal blood in the third trimester and is upregulated by antenatal corticosteroids.

OBJECTIVES: Lysophosphatidylcholine acyltransferase 1 (LPCAT1) is involved in the production of fetal lung surfactant. We have shown that LPCAT1 mRNA is present in amniotic fluid and maternal plasma and that its quantity correlates with the amniotic fluid lamellar body count. The purpose of the present study was to assay maternal plasma for the LPCAT1 protein in term and preterm pregnancies; and to measure the impact of antenatal corticosteroids. METHODS: Maternal and newborn plasma samples were obtained from 7 women admitted to the hospital for induction of labor. Maternal plasma was also obtained before administration of corticosteroids and 24 h after the second dose of corticosteroids from 12 women with premature labor and premature rupture of membranes. After sample preparation, LPCAT1 protein levels were determined using sandwich ELISA. RESULTS: We discovered LPCAT1 protein in maternal plasma in measurable quantities after 32 weeks gestation. Further, there was a rise of maternal plasma LPCAT1 in response to the clinical administration of antenatal corticosteroids. CONCLUSIONS: Quantitation of maternal plasma LPCAT1 protein offers promise in the ongoing study of fetal lung maturation.

Can ACGME Milestones predict surgical specialty board passage: an example in Obstetrics and Gynecology.

BACKGROUND: Multiple tools including Accreditation Council for Graduate Medical Education (ACGME) standardized milestones can be utilized to assess trainee and residency program performance. However, little is known regarding the objective validation of these tools in predicting written board passage. METHODS: In this retrospective study, data was gathered on n = 45 Wayne State University Obstetrics and Gynecology program graduates over the five-year period ending July 2018. United States Medical Licensing Examination (USMLE) scores, Council on Resident Education in Obstetrics and Gynecology (CREOG) in-training scores and ACGME milestones were used to predict American Board of Obstetrics and Gynecology (ABOG) board passage success on first attempt. Significance was set at p < 0.05. RESULTS: Written board passage was associated with average CREOGs (p = 0.01) and milestones (p = 0.008) while USMLE1 was not significantly associated (p = 0.055). USMLE1 <217 (Positive predictive value (PPV) = 96%). CREOGs <197 (PPV = 100%) and milestones <3.25 (PPV = 100%), particularly practice-based learning and systems-based practice milestones were most strongly correlated with board failure. Using a combination of these two milestones, it is possible to correctly predict board passage using our model (PPV = 86%). DISCUSSION: This study is the first validating the utility of milestones in a surgical specialty by demonstrating their ability to predict board passage. Residents with CREOGs or milestones below thresholds are at risk for board failure and may warrant early intervention.

The Hadlock Method Is Superior to Newer Methods for the Prediction of the Birth Weight Percentile.

OBJECTIVES: To compare a traditional ultrasound (US) method for estimated fetal weight (EFW) calculation and fetal growth restriction diagnosis with 2 newer methods for the prediction of small for gestational age (SGA) at birth. METHODS: We reviewed deliveries at our institution from January 1, 2013, to March 31, 2017. Singleton, nonanomalous, well-dated fetuses with a US examination within 2 weeks of delivery were included. Estimated fetal weights and percentiles were calculated by a traditional method (Hadlock et al; Radiology 1991; 181:129-133) and 2 newer methods: Intergrowth-21st (INTG; Ultrasound Obstet Gynecol 2017; 49:478-486) and Salomon et al (Ultrasound Obstet Gynecol 2007; 29:550-555). We calculated each method's test characteristics to predict SGA (birth weight < 10th percentile) using both traditional (EFW < 10th percentile) and receiver operating characteristic (ROC)-derived fetal growth restriction cutoffs. Mean percentile discrepancies between EFW and birth weight measurements were calculated to compare method accuracy. We hypothesized that the INTG and Salomon methods would have superior SGA prediction compared with the Hadlock method. RESULTS: Of 831 pregnancies with a US examination within 2 weeks of delivery, 138 (16.7%) were SGA at birth. Hadlock had the smallest US-birth weight percentile discrepancy (P < .001 versus both INTG and Salomon). When comparing ROC curves, the Hadlock and INTG methods performed comparably, with areas under the curve of 0.91 and 0.90 (P = .08) and optimal EFW cutoffs of the 15th and 22nd percentiles, respectively. The Salomon method performed less well, with an area under the curve of 0.82 (P < .001 versus both Hadlock and INTG methods). CONCLUSIONS: In our study cohort, the Hadlock method predicted the birth weight percentile more accurately than the INTG or Salomon methods and performed comparably with INTG to predict SGA when ROC-derived cutoffs were used.

Comparing the Hadlock fetal growth standard to the Eunice Kennedy Shriver National Institute of Child Health and Human Development racial/ethnic standard for the prediction of neonatal morbidity and small for gestational age.

BACKGROUND: The fetal growth standard in widest use was published by Hadlock >25 years ago and was derived from a small, homogeneous cohort. In 2015, The Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Study published updated standards that are specific to race/ethnicity. These do not allow for precise estimated fetal weight percentile calculation, however, and their effectiveness to predict neonatal morbidity and small for gestational age has not yet been compared to the long-standing Hadlock standard. OBJECTIVE: We compared the ability of the Hadlock standard to predict neonatal morbidity and small for gestational age at birth with that of The Eunice Kennedy Shriver National Institute of Child Health and Human Development race-/ethnicity-specific standard. Our secondary objective was to compare their performance among our Native American population, which is not accounted for in the Eunice Kennedy Shriver National Institute of Child Health and Human Development standard. STUDY DESIGN: For this retrospective study of diagnostic accuracy, we reviewed deliveries at the University of New Mexico Hospital from Jan. 1, 2013, through March 31, 2017. We included mothers with singleton, well-dated pregnancies and nonanomalous fetuses with an estimated fetal weight within 30 days of delivery. Cubic spline interpolation was performed on the Eunice Kennedy Shriver National Institute of Child Health and Human Development estimated fetal weight-percentile tables to calculate percentiles specific to the gestational day. Estimated fetal weight percentiles were then calculated using both the Hadlock and Eunice Kennedy Shriver National Institute of Child Health and Human Development race-/ethnicity-specific standards according to maternal self-identified race/ethnicity. We calculated the receiver operator area under the curve of each method to predict composite and severe composite neonatal morbidity and small for gestational age at birth (birthweight <10th percentile). As an additional measure of method accuracy, we calculated the mean ultrasound-birthweight percentile discrepancy. For Native Americans, percentiles were calculated using the Hadlock and Eunice Kennedy Shriver National Institute of Child Health and Human Development race/ethnicity standards (white, black, Hispanic, Asian), and test characteristics were calculated for each to predict neonatal morbidity and small for gestational age. RESULTS: We included 1514 women, with a mean ultrasonography-to-delivery interval of 14.4 days (±8.8) and a small for gestational age rate of 13.6% (n = 206). For the prediction of both composite and severe composite neonatal morbidity, the Hadlock method had superior performance, with higher areas under the curve than the Eunice Kennedy Shriver National Institute of Child Health and Human Development method (P < .001 for both), though neither had good discriminatory value (all areas under the curve <0.8). For the prediction of small for gestational age at birth, the Hadlock standard had higher sensitivity (61.1%) than the Eunice Kennedy Shriver National Institute of Child Health and Human Development standard, both when using the interpolated Eunice Kennedy Shriver National Institute of Child Health and Human Development method (36.2%, P < .01) and the Eunice Kennedy Shriver National Institute of Child Health and Human Development whole-week 10th percentile cutoff (46.7%, P < .01). The Hadlock method also had a higher area under the curve than the Eunice Kennedy Shriver National Institute of Child Health and Human Development interpolated method to predict small for gestational age (0.89 vs 0.88, P < .01). The Hadlock method had a lower ultrasound-birthweight percentile discrepancy than the Eunice Kennedy Shriver National Institute of Child Health and Human Development method (6.1 vs 16.5 percentile points, P < .01). Fetuses classified as growth restricted by Hadlock but not Eunice Kennedy Shriver National Institute of Child Health and Human Development had significantly higher composite morbidity than normally grown fetuses. Among Native American women, the Hadlock method had the highest area under the curve to predict composite and severe composite morbidity, while the Hadlock and all Eunice Kennedy Shriver National Institute of Child Health and Human Development race-/ethnicity-specific methods performed comparably to predict small for gestational age. CONCLUSION: Despite its publication >25 years ago, the Hadlock standard is superior to the Eunice Kennedy Shriver National Institute of Child Health and Human Development race-/ethnicity-specific standard for the prediction of both neonatal morbidity and small for gestational age.

Cantharidin is Superior to Trichloroacetic Acid for the Treatment of Non-mucosal Genital Warts: A Pilot Randomized Controlled Trial.

Condyloma Acuminatum is a sexually transmitted viral disease caused by the human papilloma virus (HPV). It is the most common viral sexually transmitted disease. In this randomized controlled trial, cantharidin was found to be more effective and better tolerated than trichloroacetic acid for the treatment of these lesions. Patients treated with cantharidin healed with less scarring than those treated with TCA (P<0.034), had less pain during treatment (P<0.01), and required fewer treatments to eradicate warts (P<0.01) when compared to Trichloroacetic acid.

Effects of medications for opioid use disorder (MOUD) on fetal brain and cranial measurements.

BACKGROUND: The use and misuse of opioids, as well as opioid use disorder (OUD) have increased remarkably among reproductive-aged and pregnant women. As many as 25% of pregnant women who report non-medical opioid use in the past month also report concurrent alcohol use. While teratogenic effects of alcohol are well established, there are limited studies evaluating fetal intracranial effects associated with medications for OUD (MOUD) and concurrent use of MOUD and alcohol during pregnancy. The objective of this study was to determine the effect of MOUD, with and without concomitant alcohol use, on fetal intracranial measurements. The type of maternal MOUD therapy (methadone vs. buprenorphine) was also examined. METHODS: This study was a secondary analysis of a prospective cohort study among participants (n = 196) assigned into three groups (MOUD [n = 94], MOUD+Alcohol [n = 47], and unexposed controls [n = 55]). Co-exposure with either methamphetamines or cocaine were exclusionary criteria; other co-exposures were carefully characterized with prospective repeated self-report measures and biomarkers. Fetal ultrasound measurements at 18-22 weeks (2nd trimester) and 28-32 weeks (early 3rd trimester) were compared among study groups. In addition to standard morphometrics, we performed specialized intracranial measurements of caval-calvarial distance (CCD), frontal lobe width (FLW), frontal lobe length (FLL), and fronto-thalamic distance (FTD). RESULTS: Brain and cranial measurements between MOUD, with or without alcohol co-exposure, and unexposed controls were generally not significantly different in multivariable analyses. Subjects in the MOUD groups had earlier gestational age at delivery and lower birth weight and birth weight percentile compared to unexposed controls with differences driven primarily by the methadone subgroup. Significant differences in standard and specialized intracranial indices at both second and third trimester as well as differences in the change of HC percentile over time were observed in the methadone subgroup compared to controls, while no differences between buprenorphine subgroup and controls were observed for any measures. CONCLUSION: Patients receiving methadone therapy might require closer monitoring during pregnancy; however, detailed imaging of the fetal brain other than the standard measurements might not be warranted.

Predictors of intention to provide abortions after OB/GYN residency training.

INTRODUCTION: Abortion is a common gynecological procedure and plays a central role in women's health and autonomy. To maintain accessibility to abortion, it is important that sufficient obstetrics and gynecology (Ob/Gyn) residents intend to provide abortion care after residency. This study identifies factors that influence a resident's intention to provide abortions (IPA) post-training. MATERIALS AND METHODS: A multiple-choice survey, addressing demographics, religious background, residency program metrics, training experience and intent to provide abortions (IPA), was answered by 409 Ob/Gyn residents. Chi-square test was performed on descriptive statistics and continuous variables were tested with ANOVA with p<0.05 considered significant. RESULTS: Residents with IPA were predominantly female (p = 0.001), training in the Northeast and West (p<0.001), identifying either as non-religious, agnostic/atheist or Jewish (p<0.01), not actively practicing their religion (p<0.001) and leaning democrats (p<0.002). Those with IPA were more likely to train at hospitals without religious affiliation (p<0.008), to train at a Ryan Program (p<0.001), to place strong emphasis on choosing a program with family planning training (p<0.001), to join programs where a significant portion of the faculty performs abortions (p<0.001) and to have completed a higher number of first trimester medical and surgical abortion procedures during the last six months of training (p<0.001). CONCLUSION: These results suggest that factors influencing a physician's intention to provide abortions are multifactorial, involving personal and program factors. A model predicting IPA is derived. To maximize IPA, residency programs can increase abortion volume, facilitate additional training and build a supportive faculty.

Trends and Evolution in Women's Health Workforce in the First Quarter of the 21st Century.

Medicine in general, and particularly women's health, is rapidly evolving. This brief communication exposes some of the changes in Obstetrics and Gynecology but are relevant to all areas of medicine. As medical knowledge grows exponentially, there may be a greater sub-specialization of physicians, residency education must adapt, physician burnout remains an issue and clinician-scientists are becoming a dying breed. In addition, healthcare delivery systems and technological innovations, such as intelligent-EMRs, promise to support physician and prevent medical errors.

Intraperitoneal Triamcinolone Reduces Postoperative Adhesions, Possibly through Alteration of Mitochondrial Function.

Adhesions frequently occur postoperatively, causing morbidity. In this noninterventional observational cohort study, we enrolled patients who presented for repeat abdominal surgery, after a history of previous abdominal myomectomy, from March 1998 to June 20210 at St. Vincent's Catholic Medical Centers. The primary outcome of this pilot study was to compare adhesion rates, extent, and severity in patients who were treated with intraperitoneal triamcinolone acetonide during the initial abdominal myomectomy (n = 31) with those who did not receive any antiadhesion interventions (n = 21), as documented on retrospective chart review. Adhesions were blindly scored using a standard scoring system. About 32% of patients were found to have adhesions in the triamcinolone group compared to 71% in the untreated group (p < 0.01). Compared to controls, adhesions were significantly less in number (0.71 vs. 2.09, p < 0.005), severity (0.54 vs. 1.38, p < 0.004), and extent (0.45 vs. 1.28, p < 0.003). To understand the molecular mechanisms, human fibroblasts were incubated in hypoxic conditions and treated with triamcinolone or vehicle. In vitro studies showed that triamcinolone directly prevents the surge of reactive oxygen species triggered by 2% hypoxia and prevents the increase in TGF-ß1 that leads to the irreversible conversion of fibroblasts to an adhesion phenotype. Triamcinolone prevents the increase in reactive oxygen species through alterations in mitochondrial function that are HIF-1α-independent. Controlling mitochondrial function may thus allow for adhesion-free surgery and reduced postoperative complications.

Potential Impact of Pass/Fail Scores on USMLE Step 1: Predictors of Excellence in Obstetrics and Gynecology Residency Training.

AIM: The study aims to determine resident applicant metrics most predictive of academic and clinical performance as measured by the Council of Resident Education in Obstetrics and Gynecology (CREOG) examination scores and Accreditation Council for Graduate Medical Education (ACGME) clinical performance (Milestones) in the aftermath of United States Medical Licensing Examination Scores (USMLE) Step 1 becoming a pass/fail examination. METHODS: In this retrospective study, electronic and paper documents for Wayne State University Obstetrics and Gynecology residents matriculated over a 5-year period ending July 2018 were collected. USMLE scores, clerkship grade, and wording on the letters of recommendation as well as Medical Student Performance Evaluation (MSPE) were extracted from the Electronic Residency Application Service (ERAS) and scored numerically. Semiannual Milestone evaluations and yearly CREOG scores were used as a marker of resident performance. Statistical analysis on residents (n = 75) was performed using R and SPSS and significance was set at P < .05. RESULTS: Mean USMLE score correlated with CREOG performance and, of all 3 Steps, Step 1 had the tightest association. MSPE and class percentile also correlated with CREOGs. Clerkship grade and recommendation letters had no correlation with resident performance. Of all metrics provided by ERAS, none taken alone, were as useful as Step 1 scores at predicting performance in residency. Regression modeling demonstrated that the combination of Step 2 scores with MSPE wording restored the predictive ability lost by Step 1. CONCLUSIONS: The change of USMLE Step 1 to pass/fail may alter resident selection strategies. Other objective markers are needed in order to evaluate an applicant's future performance in residency.

A Comparison of Methods for the Diagnosis of Fetal Growth Restriction Between the Royal College of Obstetricians and Gynaecologists and the American College of Obstetricians and Gynecologists.

OBJECTIVE: The Royal College of Obstetricians and Gynaecologists (RCOG) defines fetal growth restriction as ultrasound-estimated fetal weight less than the 10th percentile or abdominal circumference less than the 10th percentile; the American College of Obstetricians and Gynecologists (ACOG) defines fetal growth restriction as estimated fetal weight less than the 10th percentile alone. We compared each method's ability to predict small for gestational age (SGA) at birth. METHODS: For this retrospective study of diagnostic accuracy, we reviewed deliveries at the University of New Mexico Hospital from January 1, 2013, to March 31, 2017. We included mothers with singleton, well-dated pregnancies and nonanomalous fetuses undergoing indicated fetal growth restriction surveillance with an ultrasound-estimated fetal weight within 30 days of delivery. Estimated fetal weights and percentiles were calculated using the Hadlock intrauterine growth curve. Small for gestational age was defined as birth weight less than the 10th percentile based on a recent, sex-specific curve. We calculated the area under the curve, sensitivity, specificity, and positive and negative likelihood ratios for various approaches using abdominal circumference and estimated fetal weight to diagnose fetal growth restriction, including the definitions endorsed by ACOG and RCOG. RESULTS: We included 1,704 pregnancies with a mean ultrasonography-to-delivery interval of 14.0 days (±8.6). There were 235 SGA neonates (13.8%). The rate of fetal growth restriction was 13.6% when using ACOG's criteria and 16.9% according to RCOG's criteria (P=.007). The area under the curve of RCOG's diagnostic approach was 0.78 (95% CI 0.76-0.80), which was higher than ACOG's (0.76, 95% CI 0.74-0.78, P=.01). Sensitivities and specificities of the various methods were similar. Adopting estimated fetal weight or abdominal circumference less than the 10th percentile instead of estimated fetal weight alone to predict SGA at birth would correctly identify one additional case of SGA for each 14 patients assessed. CONCLUSION: The diagnostic approach endorsed by RCOG is a marginally better predictor of SGA at birth compared with the method endorsed by ACOG. Future research should consider the potential benefits and harms of the different methods in different populations.

N-methyl-D-aspartate glutamate receptor mediates spontaneous and angiotensin II-stimulated ovine fetal swallowing.

BACKGROUND: In adult rats, N-methyl-D-aspartate (NMDA) receptors have been implicated in the central control of body fluid homeostasis, as intracerebroventricular (ICV) injection of NMDA receptor antagonists suppresses stimulated drinking behavior. Fetal swallowing occurs at a significantly higher rate as compared to adult drinking, contributing to amniotic fluid volume regulation and fetal gastrointestinal development. The aim of present study was to determine the role of central NMDA receptors in the modulation of fetal swallowing activity. METHODS: Eight time-dated pregnant ewes and fetuses were chronically prepared with fetal vascular and ICV catheters, electrocorticogram (ECoG), and esophageal electromyogram electrodes and studied at 130 +/- 1 days' gestation. Following an initial 2-hour baseline period (time 2 h), the NMDA receptor antagonist, dizocipline (1 mg), was injected ICV. At time 4 h, the dose of dizocipline was repeated, together with angiotensin II (AngII, 6.4 microg). Fetal swallowing was monitored for 2 hours after each injection. Four of these fetuses also received an identical control study (on an alternate day) in which dizocipline was replaced with artificial cerebrospinal fluid (aCSF). RESULTS: ICV dizocipline injection nearly abolished spontaneous fetal swallowing activities (0.6 +/- 0.1 to 0.2 +/- 0.1 swallows/min; P < .001). ICV AngII in the presence of dizocipline did not demonstrate a dipsogenic effect on fetal swallowing (0.1 +/- 0.1; P < .001). In the control study, ICV injection of aCSF did not change fetal swallowing activity (1.0 +/- 0.1 swallows/min), while ICV AngII resulted in a significant increase in fetal swallowing (2.0 +/- 0.1 swallows/min; P < .001). CONCLUSIONS: This study demonstrates that central NMDA-glutamate receptor-mediated activity contributes to the high rate of spontaneous and AngII-stimulated fetal swallowing. We speculate that reduced NMDA receptor expression within the forebrain dipsogenic neurons may account for observed differences in drinking activities between the fetus/neonate and the adult.

Neuronal NO modulates spontaneous and ANG II-stimulated fetal swallowing behavior in the near-term ovine fetus.

Spontaneous fetal swallowing occurs at a markedly higher rate compared with spontaneous adult drinking activity. This high rate of fetal swallowing is critical for amniotic fluid volume regulation. Central NO is critical for maintaining the normal rate of fetal swallowing, as nonselective inhibition of NO (with central N(G)-nitro-L-arginine methyl ester) suppresses spontaneous and angiotensin II (ANG II)-stimulated swallowing. We sought to differentiate the contributions of central endothelial vs. neuronal NO in the regulation of spontaneous and stimulated fetal swallowing, using a selective neuronal NO synthase (nNOS) inhibitor. Six time-dated pregnant ewes and fetuses were chronically prepared with fetal vascular and intracerebroventricular (i.c.v.) catheters and electrocorticogram (ECoG) and esophageal electromyogram electrodes and studied at 130 +/- 1 days of gestation. After an initial 2-h baseline period (0-2 h), the selective nNOS inhibitor N-propyl-L-arginine (NPLA) was injected i.c.v. (2-4 h). At 4 h, the dose of NPLA was repeated, together with ANG II, and fetal swallowing was monitored for a final 2 h. Four fetuses also received an identical control study (on an alternate day) in which NPLA was replaced with artificial cerebrospinal fluid (aCSF). Suppression of nNOS by i.c.v. NPLA significantly reduced mean (+/- SE) spontaneous fetal swallowing (1.35 +/- 0.12 to 0.50 +/- 0.07 swallows/min; P < 0.001). Injection of ANG II in the presence of NPLA had no dipsogenic effect on fetal swallowing (0.68 +/- 0.09 swallows/min). In the aCSF study, i.c.v. aCSF did not change fetal swallowing (0.93 +/- 0.10 vs. 0.95 +/- 0.09 swallows/min), whereas i.c.v. ANG II resulted in a significant increase in the rate of fetal swallowing (2.0 +/- 0.04 swallows/min; P = 0.001). We speculate that the suppressive dipsogenic effects of central NPLA indicate that spontaneous and ANG II- stimulated fetal swallowing is dependent on central nNOS activity.

Pharmacokinetics of ionized versus total magnesium in subjects with preterm labor and preeclampsia.

OBJECTIVE: Intravenous magnesium sulfate is widely used in obstetrics for the treatment of both preterm labor and preeclampsia. Although therapeutic levels of total magnesium have been proposed, the levels remain controversial. Because the active form of magnesium is the free or ionized form, it is essential to determine whether ionized magnesium and total magnesium levels are highly correlated in vivo. We sought to examine the correlation between ionized magnesium and total magnesium under basal and therapeutic conditions and to define the initiation and elimination pharmacokinetics of both forms during intravenous magnesium sulfate infusion. STUDY DESIGN: Twenty-four singleton pregnant patients who were candidates for magnesium sulfate were studied (preterm labor, 15; preeclampsia, 9). Serial blood samples were taken before the magnesium sulfate infusion, during the first 4 hours after the initiation of magnesium sulfate infusion and for 4 hours after the discontinuation of the infusion. RESULTS: Baseline levels of total magnesium and ionized magnesium were not different between patients with preterm labor and with preeclampsia. Among patients with preeclampsia, although not patients with preterm labor, the initial apparent volume of distribution was significantly smaller for total magnesium than for ionized magnesium (16,397 +/- 1441 vs 23,856 +/- 2745 mL, respectively; P =.03), and the elimination half-life was greater for total magnesium as compared to ionized magnesium (707 +/- 160 vs 313 +/- 29 minutes;P <.05). Linear regression analysis demonstrated a lack of correlation between ionized magnesium and total magnesium during the pretreatment period and during the steady state infusion for both preterm labor and preeclampsia. CONCLUSION: The measurement of total magnesium may not be adequate for the titration of therapeutic magnesium infusions in patients with preeclampsia or preterm labor because of the lack of correlation between total magnesium and the physiologically active ionized magnesium. Further studies may determine whether the measurement of ionized magnesium is a superior method for following the adequacy and safety of the treatment of preeclampsia and preterm labor.

Cardiovascular regulation and expressions of NO synthase-tyrosine hydroxylase in nucleus tractus solitarius of ovine fetus.

The purpose of this study was to examine cardiovascular responses to fourth cerebral ventricle (4V) administration of nitroglycerin (NTG) or an inhibitor of nitric oxide (NO) synthase (NOS) in the near-term ovine and to determine whether, during birth, neuronal NOS (nNOS) is induced in noradrenergic A1 neurons in the medial nucleus tractus solitarius (mNTS). In chronically instrumented fetal sheep, 4V injection of NTG (1.2 nmol), an NO donor, produced an arterial blood depressor and a moderate decrease in heart rate. Arterial blood pressure is increased by 4V administration of NG-nitro-L-arginine methyl ester (10 nmnol), an inhibitor of NOS, in fetuses. Sections of the medulla from fetuses and newborn lambs were examined by using immunolabeling with tyrosine hydroxylase (TH) antibody combined with NADPH diaphorase (NADPHd) histochemistry, a marker of nNOS activity. The NADPHd-positive cells and TH-positive cells containing NADPHd reactivity were significantly increased in the mNTS of newborns compared with the fetuses. The results suggest that during birth, there is upregulation of NADPHd/nNOS in the noradrenergic neurons of mNTS resulting in a centrally mediated reduction of fetal arterial blood pressure.