Final Stage Of Gestation Research Articles

Lung histopathology and scanning electron microscopy in newborn piglets from sows vaccinated with MLV PRRSV vaccine in the final stage of gestation

Lung histopathology and scanning electron microscopy in newborn piglets from sows vaccinated with MLV PRRSV vaccine in the final stage of gestation

Evaluation of Genotoxic Effect and Antigenotoxic Potential against DNA Damage of the Aqueous and Ethanolic Leaf Extracts of Annona muricata Using an In Vivo Erythrocyte Rodent Micronucleus Assay.

Annona muricata have been extensively used in traditional medicine to treat multiple diseases, including cancers. This study evaluated the genotoxic potential and antigenotoxic activities of A. muricata aqueous and ethanolic leaf extracts by employing an in vivo erythrocyte rodent micronucleus assay. Different doses (187.5, 375, and 750 mg/kg) of both extracts were administered orally for 5 days alone and combined with cyclophosphamide (CP, 60 mg/kg) to BALB/c mice. Also, it was administered orally to Wistar rats for 5 days through the final stage of gestation. No genotoxic or cytotoxic effects were observed in the two adult rodent models when A. muricata was administered orally nor in newborn rats transplacentally exposed to the extracts. Moreover, A. muricata aqueous and ethanolic leaf extracts demonstrated a protective effect against CP-induced DNA damage. Due to its lack of genotoxic effect and its capacity to decrease DNA damage, A. muricata is likely to open an interest field regarding its potential safe use in clinical applications.

A novel surgical toxicological-free model of diaphragmatic hernia in fetal rats.

Teratogen-induced congenital diaphragmatic hernia (CDH) rat models are commonly used to study the pathophysiology. We have created a new and reliable surgically induced diaphragmatic hernia (DH) model to obtain a purely mechanical DH rat model, and avoid the confounding teratogen-induced effects on the lung development. Fetal DH was surgically created on fetuses at E18.5 and harvested at E21.5 in rats. Four groups were evaluated (n = 16): control (CONT), control exposed to Nitrofen (CONT NIT), DH surgically created (DH SURG), and CDH Nitrofen (CDH NIT). Body weight, total lung weights, and their ratio (BW, TLW, and TLBR) were compared. Air space (AS), parenchyma (PA), total protein, and DNA contents were measured to verify lung hypoplasia. Medial wall thickness (MWT) of pulmonary arterioles was also analyzed. DH SURG showed significant hypoplasia (decreased in total protein and DNA) vs CONT (p < 0.05); DH SURG vs CDH NIT were similar in TLW and TLBR. DH SURG has less AS than CONT (p < 0.05) and similar PA compared to CONT NIT and CDH NIT, MWT were similarly increased in CONT NIT, DH SURG, and CDH NIT. This novel surgical model generates fetal lung hypoplasia contributing to the study of the mechanical compression effect on fetal lung development in DH. There is a critical need to develop a surgical model in rat to complement the findings of the well-known Nitrofen-induced CDH model. This experimental study is pioneer and can help to understand better the CDH pathophysiological changes caused by herniated abdominal viscera compression against the lung during the final stage of gestation in CDH fetuses, and also to develop more efficient treatments in near future.

35 Effect of Late Gestational Heat Stress on Placental Characteristics in Dairy Cattle

Abstract To determine the effects of late gestation heat stress on placental development, dairy cows were exposed to heat stress (HT, shade) or cooled (CL, shade, fans and soakers) during the final 46 d pre-calving on the University of Florida dairy facility (temperature-humidity index; THI &amp;gt;68). We hypothesize heat stress (or lack of heat abatement) will reduce placental efficiency and in turn increase placental weight, surface area, and volume. At expulsion all placentae were collected and total placental weight was determined as well as individual cotyledonary weights, surface areas, and volume. In addition, the total number of total cotyledons was recorded and cotyledonary color and placental growth abnormalities (i.e. teratomas) were recorded and photographed. All data were analyzed using PROC MIXED in SAS. In addition, associations between parameters were determined by calculating Pearson Correlation Coefficients using SAS. Placentae from HT cows had a higher total placental weight, higher non-vascular membrane weight, higher total cotyledonary weight, higher total cotyledonary volume, and a higher incidence of teratomas than those from CL cows (P &amp;lt; 0.05). HT cows also had placentae with a significantly greater average cotyledonary weight and volume (P &amp;lt; 0.05). HT cows tended to have a greater incidence of color abnormalities in the placenta (P &amp;lt; 0.075). In addition, HT cows had significantly lighter calves at birth (P &amp;lt; 0.05). These data demonstrate that heat stress (or lack of heat abatement) impacts placental growth during the final stages of gestation, resulting in heavier placentae, an increase in cotyledonary weight and volume, but not an increase in the total number of cotyledons or total cotyledonary surface area. These placental alterations ultimately resulted in lighter calves at birth.

Soluble guanylate cyclase stimulation in late gestation does not mitigate asymmetric intrauterine growth restriction or cardiovascular risk induced by placental ischemia in the rat.

Stimulation of soluble guanylate cyclase (sGC) improves fetal growth at gestational day 20 in the reduced uterine perfusion pressure (RUPP) rat model of placental ischemia suggesting a role for sGC in the etiology of intrauterine growth restriction (IUGR). This study tested the hypothesis that stimulation of sGC until birth attenuates asymmetric IUGR mitigating increased cardiovascular risk in offspring. Sham or RUPP surgery was performed at gestational day 14 (G14); vehicle or the sGC stimulator Riociguat (10 mg/kg/day sc) was administered G14 until birth. Birth weight was reduced in offspring from RUPP [intrauterine growth restricted (IUGR)], sGC RUPP (sGC IUGR), and sGC Sham (sGC Control) compared with Sham (Control). Crown circumference was maintained, but abdominal circumference was reduced in IUGR and sGC IUGR compared with Control indicative of asymmetrical growth. Gestational length was prolonged in sGC RUPP, and survival at birth was reduced in sGC IUGR. Probability of survival to postnatal day 2 was also significantly reduced in IUGR and sGC IUGR versus Control and in sGC IUGR versus IUGR. At 4 mo of age, blood pressure was increased in male IUGR and sGC IUGR but not male sGC Control born with symmetrical IUGR. Global longitudinal strain was increased and stroke volume was decreased in male IUGR and sGC IUGR compared with Control. Thus late gestational stimulation of sGC does not mitigate asymmetric IUGR or increased cardiovascular risk in male sGC IUGR. Furthermore, late gestational stimulation of sGC is associated with symmetrical growth restriction in sGC Control implicating contraindications in normal pregnancy.NEW & NOTEWORTHY The importance of the soluble guanylate cyclase-cGMP pathway in a rat model of placental ischemia differs during critical windows of development, implicating other factors may be critical mediators of impaired fetal growth in the final stages of gestation. Moreover, increased blood pressure at 4 mo of age in male intrauterine growth restriction offspring is associated with impaired cardiac function including an increase in global longitudinal strain in conjunction with a decrease in stroke volume, ejection fraction, and cardiac output.

Isolation and Characterization of Pancreatic Canine Fetal Cells at the Final Stage of Gestation.

The incidence of diabetes mellitus in dogs is increasing in recent years, mainly because of genetic and/or environmental factors, including endocrine disorders (like in humans); failure of suitable control of blood sugar levels, which triggers hyperglycemia; glycosuria and weight loss, which demands the development of innovative treatments to cure or treat this complex disease in dogs. The present study established for the first time a protocol to obtain and characterize cells derived from pancreas of canine fetuses. Those fetuses do not have a defined breed and were at the final stage of gestation. The protocol aims to provide morphological data to enable future applications of these cells for therapeutic approaches. In cell culture, pancreatic cells showed a fibroblast-like appearance with a mono-layered growth pattern and were not tumorigenic. They exhibited a positive expression for the pluripotent proliferation markers NANOG and PCNA and expressed PDX1, a transcription factor that is important for activation of the insulin gene promoter. In addition, Tyrosine Hydroxylase-positive (TH+) sympathetic nerve fibers were identified. Histologically, the pancreatic epithelium was developed, pancreatic glands in the fetuses were like those in the parenchyma of postconception dogs and pancreatic islets were unevenly distributed and organized in small clusters along the glands close to the vasculature. Staining with dithizone indicated the presence of insulin in the cells. A large number of beta cells were confirmed by immunofluorescence. In conclusion, the canine fetal pancreas cells could be an alternative and adequate source of cell lineages for stem cell therapies for diabetes treatment. Anat Rec, 302:1409-1418, 2019. © 2018 Wiley Periodicals, Inc.

Partitioning components of maternal growth to determine efficiency of feed use in gestating sows.

The objective of this study was to evaluate the effect of parity and stage of gestation on predicted maternal weight gain and efficiency of feed use in gestating sows from a commercial sow farm. A total of 712 females (Camborough, PIC, Hendersonville, TN) were group-housed from days 5 to 112 of gestation and individually fed with electronic sow feeders (ESF). Feed intake and body weight (BW) were recorded daily throughout gestation via the ESF and a scale located in an alleyway just after sows exited the feeding station. Gilts (parity 1) and sows received 6,450 or 7,418 kcal ME, respectively, whereas 12 thin females received 9,675 kcal ME per day. Maternal weight gain, not including products of conceptus, and feed efficiency were predicted using a series of equations to model nutrient utilization in gestation. Data were divided into 3 parity groups: 1, 2, and 3+, and gestation was divided into 3 periods: days 5 to 39, 40 to 74, and 75 to 109. After dividing energy requirements into tissue pools for maintenance, growth (maternal protein and fat deposition), and products of conceptus, the greatest portion of the energy requirement was for maintenance and maternal growth. The predicted energy used for maternal protein and fat deposition decreased (P < 0.05) in each period of gestation, regardless of parity group. Parity 2 sows had the greatest (P < 0.05) energy use for maternal protein and fat deposition in all stages of gestation, whereas parity 1 sows had a negative energy balance during the final stage of gestation. Parity 1 sow BW increased (P < 0.05) in each period of gestation; however, parity 2 and 3+ sow BW remained static from days 75 to 109 of gestation. Parity 3+ sows had the greatest (P < 0.05) maternal BW throughout the course of gestation compared with other parity groups. Regardless of parity, maternal ADG decreased (P < 0.05) from days 40 to 74 before increasing (P < 0.05) during the final stage of gestation. Parity 1 sows had the greatest (P < 0.05) ADG in all gestation periods. Parity 1 sow G:F decreased (P < 0.05) in each sequential period of gestation. Parity 2 and 3+ sow G:F decreased (P < 0.05) from days 40 to 74 but improved (P < 0.05) during the final period of gestation. Parity 1 sow G:F was greater than parity 2 and 3+ sows in most gestation periods. Overall, this study and subsequent prediction models show how stage of gestation and parity affect the growth of different tissue pools, sow maternal BW, and feed usage throughout the course of gestation.

&lt;b&gt;Damage caused by exposure to propofol during gestation of mice

Literature shows that surgical procedure could be necessary at any stage of pregnancy and can cause adverse effects on the mother and fetus. One of the most used anesthetics in surgical centers is propofol however; the safety during pregnancy has not been completely established. The objective of this study was to investigate the possible toxic and teratogenic effects on the intrauterine and post-natal development of mice exposed to the dose of 15 mg kg-1 propofol on the caudal vein fifth, tenth and fifteenth day of gestation. A significant reduction in weight gain was observed in female mice who received a 15 mg kg-1 dose of propofol on the fifth gestational day. A higher rate of embryonic loss post implantation and resorption was also observed in this group. In regards to physical development, the anesthetic increased significantly the offspring weight gain, the time in which pinna detachment occurred, and the anogenital distance of pups whose females received propofol on the fifteenth day of gestation. Based on these results, we concluded that administration of propofol in the beginning stages of gestation increases the number of abortions and promotes alterations in the physical development of pups whose mothers were anesthetized in the final stages of gestation.

Histerocele diafragmática en una gata gestante: Reporte de un caso

A case of animal care, feline, adult, female is described, with diagnosis of chronic diaphragmatic hernia with the gravid uterus in the final stage of gestation as part of the hernial content. Gradual fetal growth during pregnancy led to significant respiratory impairment. The severity of the condition necessitated a surgical interruption of gestation with posterior herniorrhaphy with peritoneal flap, but it did not succeed and the animal died at the end of the surgical procedure. The death was attributed to the chronicity and severity of the clinical condition in which it was found. This report highlights the importance of immediate correction of diaphragmatic hernias and prenatal follow-up during pregnancy.

Diámetro Biparietal en Fetos a Término en Varias Razas de Perros

El presente estudio tuvo por objetivo la determinación de la medición ecográfica cuantitativa del diámetro biparietal de fetos a término en perras. Se trabajó con 181 informes ecográficos de varias razas de perras en gestación cuyos fetos tenían menos de 210 latidos por minuto, y que fueron examinados en el consultorio de ecografía de la Clínica de Animales Menores de la Facultad de Medicina Veterinaria, Universidad Nacional Mayor de San Marcos, Lima, Perú, entre los años 2000-2014.

Pre- and post-partum seric biochemical variables of Lacaune ewes naturally infected by gastrointestinal parasites

The main objective of the present study was to evaluate the biochemical profile of the Lacaune ewes naturally infected by gastrointestinal parasites in the pre- and post-partum period. Ewes with similar age and weight, primiparas in the final stage of gestation, totaling 24 animals were selected. Sampling days were 10 and 2 for pre-partum and 2, 6, and 12 days for post-partum to evaluate total proteins, albumin, globulin, cholesterol, triglycerides, and urea levels, in addition to thiobarbituric acid reactive substances (TBARS), reactive oxygen species (ROS), and glutathione S-transferase (GST). Fecal examination by McMaster method was performed during bleeding, and based on the number of eggs per gram of feces (EPG), the animals were divided into two groups: A (sheep with EPG 1000) to evaluate the effect of the parasitic load. Statistical analyses of biochemical parameters and EPG were performed taking into account groups, evaluated each time of sampling and over time, as well as without considering the groups, comparing pre- and post-partum and over time. It was possible to verify that the influence of time had a significant (P < 0.01) impact on cholesterol, triglycerides, total proteins, albumin, globulin, TBARS, and GST specifically among sampling time. When time of collection was considered, there were some differences between groups A and B for the variables: triglycerides (day 6 post-partum) and globulin (day 2 pre-partum). It is concluded that the parasitic load did influence seric levels of the urea, triglycerides, and globulins on a determined time.

Genotoxic evaluation of pirfenidone using erythrocyte rodent micronucleus assay

Pirfenidone is a non-steroidal antifibrotic compound that has been proposed in clinical protocols and experimental studies as a pharmacological treatment for fibroproliferative diseases. The objective of this study was to determine the genotoxicity or cytotoxicity of three doses of pirfenidone using the micronuclei test in peripheral blood erythrocytes of rodent models. Pirfenidone was administered orally to Balb-C mice for 3days, and also was administered topically to hairless Sprague Dawley rats during the final stage of gestation. Mice were sampled every 24h over the course of 6days; pregnant rats were sampled every 24h during the last 6days of gestation, and pups were sampled at birth. Blood smears were analyzed and the frequencies of micronucleated erythrocytes (MNEs), micronucleated polychromatic erythrocytes (MNPCEs), and the proportion of polychromatic erythrocytes (PCEs), were recorded in samples from mice, pregnant rats and rat neonates. Increases in MN frequencies (p<0.03) were noted only in the positive control groups. No genotoxic effects or decreased PCE values were observed neither in newborn rats transplacentally exposed to pirfenidone, or in two adult rodent models when pirfenidone was administered orally or topically.

The effect of dexamethasone on the activity of 11beta-hydroxysteroid dehydrogenase in the foetal rabbit lung during the final stage of gestation.

The effect of dexamethasone on the activity of 11beta-hydroxysteroid dehydrogenase in the foetal rabbit lung during the final stage of gestation.

Acute Phase Proteins in Experimentally Induced Pregnancy Toxemia in Goats

The present work aimed to study the behavior of acute phase proteins (haptoglobin, serum amyloid A, acid soluble glycoprotein, fibrinogen, and albumin) in fasting-induced pregnancy toxemia in goats and their relationship with classical indicators of this disorder such as beta-hydroxybutyrate and nonesterified fatty acids in the blood and decreased urine pH and ketonuria. Twelve adult Murciano-Granadina goats at the final stage of gestation were used in this experiment. Pregnancy toxemia was induced in 6 goats by fasting for 72 hr. The other 6 animals were used as control group. Ketonuria was present in 4 out of 5 fasting animals at 24 hr and in all fasting animals at 48 hr of fasting. Serum nonesterified fatty acids were significantly increased at 24, 48, and 72 hr of fasting. Beta-hydroxybutyrate and haptoglobin achieved significantly increased concentrations at 48 hr and 72 hr, respectively, remaining increased during the entire study. Serum amyloid A, acid soluble glycoprotein, fibrinogen, and albumin were not affected by fasting. In conclusion, acute phase proteins (including haptoglobin) seemed not to have an advantage over traditional markers in diagnosis of fasting-induced pregnancy toxemia in goats.

Divided PE and HDF Saved a Patient with Acute Pancreatitis Caused by Hyperlipidemia in the Final Stage of Gestation

Acute pancreatitis is rare during pregnancy with hyperlipidemia found in only about 100 cases reported in Japan. We used divided plasma exchange (PE) and hemodia–filtration (HDF) for treatment. A 28–year–old pregnant woman was examined at 29 weeks of gestation. Laboratory data on admission revealed an increased white blood cell count of 16,300/mm3, total cholesterol 1,072mg/dl, triglycerides 4,288mg/dl, serum amylase 850IU/L, elastase 1,002ng/dL, and phospholipase A2 2,850ng/dL. The acute pancreatitis diagnosis with CT evaluation was grade IV. In addition, the Acute physiology and chronic health evaluation (APACHE) II score was 14 points, Sequential organ failure assessment (SOFA) score 7 points, Ranson score 4 points. First, we performed PE and HDF, but filtration was impossible due to hyperlipidemia. Subsequently, we succeeded with our new method, divided PE and HDF. The patient was discharged from the hospital on the 17th hospital day. Both the patient and her baby are in good health. This is the first report of a new therapy for acute pancreatitis during pregnancy with hyperlipidemia. The experience of this case and a review of the English literature suggested that divided PE and HDF are recommended to treat this rare hyperlipidemia.

超音波診断装置を用いた妊娠末期におけるホルスタイン種クローン胚由来産子の体重モニタリング法に関する研究

超音波診断装置を用いた妊娠末期におけるホルスタイン種クローン胚由来産子の体重モニタリング法に関する研究

Rethinking Primary Prevention of Atherosclerosis-Related Diseases

Crucial advances in our understanding of basic pathogenic mechanisms involved in atherogenesis have been achieved during the past 2 decades. The historical hypothesis of pathogenesis (“lipid accumulation”) has evolved to integrate several causal events contributing to the initiation and evolution of atherosclerosis. Vascular inflammation and apoptosis may play a joint pivotal role in its progression and onset. Hypercholesterolemia and hypertension have synergistic deleterious effects on coronary endothelial function.1 Impaired fasting glucose, triglycerides and triglyceride-rich lipoprotein remnants, lipoprotein(a), homocysteine, and high-sensitivity C-reactive protein (hsCRP) might contribute to an increased risk of atherosclerosis.2 The disease also has been related to infiltration of immune cells, which are involved in both systemic and local, innate as well as adaptive, immune responses.3 Distinct pathways of atherothrombosis seem to develop at different sites of the vascular system (brain, heart, and peripheral circulation). Endothelial dysfunction induced by cardiovascular risk factors is considered to be 1 of the earliest stages in vascular damage and is associated independently with cardiovascular events.4 There is a synergic action between genetic, ambient, local, and systemic factors, and ultimately the progression of atherosclerosis is responsible for coronary heart disease (CHD) and its complications (such as unstable “in crescendo” angina, myocardial infarction, and sudden death), peripheral arterial disease, and ischemic stroke. The evolution of atherosclerosis, however, is characterized by a long lag time between onset and clinical manifestation, thereby providing an opportunity for implementation of early detection, prevention, and intervention strategies. Because the development of atherosclerosis commences early in humans, we need to rethink the timing of what is currently considered to be “primary” prevention of atherosclerosis-related diseases. It is likely that we need to start administering effective treatments much earlier than previously assumed. Indeed, much attention would be important when subjects are in a state of wellness before the …

Ultrasonographic Monitoring of Nuclear Transferred Fetal Weight during the Final Stage of Gestation in Holstein Cows

Dystocia or stillbirth accompanied by Large Offspring Syndrome (LOS) occurs rather frequently in Holstein nuclear transferred calves. In regard to prophylaxes, nuclear transferred Holstein fetuses were monitored with ultrasonography during the final stage of gestation. Fetal weight was estimated weekly based on the fetal metacarpal width using ultrasonography. Fourteen Holstein cows pregnant with Holstein nuclear transferred fetuses were the subjects of this experiment. The fetal weight was estimated by measuring the fetal metacarpal width during the last month of gestation according to the expected date of parturition. Measurements were performed on a weekly basis. The ultrasound-estimated metacarpal width and body weight of 13 of the fetuses in the last week of gestation (30.2+/-2.2 mm, 50.0+/-4.7 kg) were similar to the actual measurement immediately after birth (30.0+/-2.1 mm, 51.2+/-5.5 kg). These results indicate that ultrasonographic monitoring within a week of parturition to is accurate for estimating fetal weight. Prediction of LOS with ultrasonography contributes to reliable a diagnostic method that minimizes syndrome-related gyneco-obstetric complications at parturition with the aid of appropriate treatments.

Epithelial Lymphocyte and Macrophage Distribution in the Adult and Fetal Equine Lung

Leucocytes in the lung epithelium play an important role in the ability of an animal to respond appropriately to inhaled pathogens. The distribution of lymphoid and myeloid cells associated with the lung epithelium was examined immunohistochemically throughout the respiratory tract of four horses, comprising two adults from an abattoir, one pregnant mare, and her fetus (in the final stage of gestation). Cross and tangential cryosections were labelled with monoclonal antibodies against T-cell, B-cell, macrophage/dendritic myeloid cell, and major histocompatibility Class (MHC) II surface antigens. Cell numbers were determined by microscopy. In the three adult horses, epithelial CD3+ T-cell numbers decreased progressively from the upper to the lower respiratory tract, but in the fetus there were low numbers of T cells (at most, 10% of those seen in the adult airways) and little variation in different parts of the respiratory tract. MHC Class II was expressed on the airway epithelium of the two abattoir horses, but not that of the mare and her fetus. In these two animals occasional large, mostly irregularly-shaped, Class II-positive cells were seen. Very few epithelium-associated cells in any animal were labelled by anti-CD21 antibody, which identifies B cells, or anti-myeloid cell antibodies; an anti-rat macrophage antibody (ED2) was shown, for the first time, to identify mature equine alveolar macrophages. Despite the small number of animals, the results suggest that in normal adult horses the greatest numbers of epithelial T cells are found where there is greatest contact with airborne antigens, and that there is constitutive epithelial MHC Class II expression. The low level of MHC Class II expression in the fetus, together with the reduced numbers of T cells, was consistent with the suggestion that the fetal immune system requires exposure to airborne stimuli for full development. The low level of MHC Class II expression in the mare may have reflected the immunosuppression that accompanies pregnancy.

Cocaine's lethality increases during late gestation in the rat: A study of “critical periods” of exposure

OBJECTIVE: Cocaine-associated morbidities in pregnant women (e.g., abruptio placentae, hypertension, seizures) occur mostly during the final stages of gestation. The purpose of our study was to determine whether cocaine's toxicity and blood levels varied as a function of “critical periods” of exposure during gestation. STUDY DESIGN: To evaluate mortality rates, pregnant Long-Evans rats received subcutaneously 30, 40, or 50 mg/kg cocaine hydrochloride twice daily (C30, C40, and C50 groups) either during gestational days 7 to 13 (midgestation) or gestational days 14 to 20 (late gestation) ( n = 9 to 20 per group). Serum levels of the cocaine metabolite benzoylecgonine were examined in other groups of rats on either gestational day 13 (mid) or day 20 (late) in the C30 treatment condition ( n = 5 and 10 per group). RESULTS: There were no maternal mortalities in the midgestation groups at any dose. In contrast, the late-gestation groups showed a dramatic dose-dependent effect, with maternal mortality rates of 0%, 40%, and 72% in the C30, C40, and C50 groups. The late-gestation group had higher benzoylecgonine levels than the midgestation groups did. CONCLUSIONS: Late gestation was associated with higher maternal mortality rates and higher benzoylecgonine levels, indicating that some underlying physiologic change enhanced cocaine's toxicity as pregnancy progressed. This increased sensitivity to cocaine may be mediated by estrogen or progesterone, suggesting that the cocaine-abusing woman is at increased risk for cocaine-induced morbidities whenever levels of these hormones are elevated, such as during the final stages of pregnancy or possibly when taking oral contraceptives. (Am J Obstet Gynecol 1997;176:901-6.)