The role of n-3 fatty acids in gestation and parturition

Preterm birth is the most common cause of low infant birth weight and infant morbidity and mortality. Evidence from human and animal studies indicates that essential fatty acids of both the n-3 and n-6 series, and their eicosanoid metabolites, play important and modifiable roles in gestational duration and parturition, and n-3 fatty acid intake during pregnancy may be inadequate. Prostaglandins (PG) of the 2-series are involved in parturition and connective tissue remodeling associated with cervical maturation and rupture of membranes. In the absence of infections, preterm birth is characterized by lower reproductive tissue PG production and decreased inducible cyclooxygenase expression. Women who deliver prematurely have increased pools of n-6 fatty acid and decreased n-3 fatty acids, despite the lower PG production. Several human pregnancy supplementation trials with n-3 fatty acids have shown a significant reduction in the incidence of premature deliver and increased birth weight associated with increased gestational duration. Supplementation with long chain n-3 fatty acids such as docosahexaenoic acid may be useful in prolonging the duration of gestation in some high-risk pregnancies. Evidence presented in this review is discussed in terms of the roles of dietary n-3 and n-6 fatty acids in gestation and parturition, mechanisms by which they may influence gestational duration and the human trials suggesting that increased dietary long-chain n-3 fatty acids decrease the incidence of premature delivery.     

Rainfall, food abundance and timing of parturition in African bats

We used published results from studies in Africa to test the hypothesis that the timing of parturition in the Chiroptera is constrained by rainfall. Comparison of year-round rainfall and insect data at various latitudes showed that insect abundance peaks approximately a month after peak rainfall. A similar comparison of parturition time to rainfall showed that with the possible exception of the molossids, the Microchiroptera commonly give birth a month before peak rainfall. With an average 6-week lactation period in the Microchiroptera, the timing of parturition is such that young bats are weaned just before the period of maximum insect abundance. We suggest that the needs of the young in this post-weaning period may be more important than the energetic demands of lactation on the mother in determining the timing of parturition on an evolutionary scale. A similar conclusion is implied for the African Megachiroptera, but there is insufficient information on their reproduction to adequately test the main hypothesis for these bats. Received: 4 October 1996 / Accepted: 14 March 1997     

An evolutionary genomic approach to identify genes involved in human birth timing

Coordination of fetal maturation with birth timing is essential for mammalian reproduction. In humans, preterm birth is a disorder of profound global health significance. The signals initiating parturition in humans have remained elusive, due to divergence in physiological mechanisms between humans and model organisms typically studied. Because of relatively large human head size and narrow birth canal cross-sectional area compared to other primates, we hypothesized that genes involved in parturition would display accelerated evolution along the human and/or higher primate phylogenetic lineages to decrease the length of gestation and promote delivery of a smaller fetus that transits the birth canal more readily. Further, we tested whether current variation in such accelerated genes contributes to preterm birth risk. Evidence from allometric scaling of gestational age suggests human gestation has been shortened relative to other primates. Consistent with our hypothesis, many genes involved in reproduction show human acceleration in their coding or adjacent noncoding regions. We screened >8,400 SNPs in 150 human accelerated genes in 165 Finnish preterm and 163 control mothers for association with preterm birth. In this cohort, the most significant association was in FSHR, and 8 of the 10 most significant SNPs were in this gene. Further evidence for association of a linkage disequilibrium block of SNPs in FSHR, rs11686474, rs11680730, rs12473870, and rs1247381 was found in African Americans. By considering human acceleration, we identified a novel gene that may be associated with preterm birth, FSHR. We anticipate other human accelerated genes will similarly be associated with preterm birth risk and elucidate essential pathways for human parturition.     

Interleukin-8 release from human gestational tissue explants: effects of gestation, labor, and chorioamnionitis.

Interleukin-8 (IL-8) is a chemotactic cytokine that has been implicated in the process of human parturition, including the processes of cervical ripening and rupture of fetal membranes. In this study, the in vitro release of IL-8 from human amnion, choriodecidua, and placenta tissues obtained before and after spontaneous labor onset both at term and preterm, was assessed. The effect of chorioamnionitis on IL-8 release was also established. All tissue explants examined released IL-8; however, IL-8 release from choriodecidual explants was significantly (p < 0.02) greater than that observed from amnion and placenta. Furthermore, choriodecidual IL-8 release was significantly (p < 0.001) greater from term tissues (850 +/- 134.4 ng/mg DNA, n = 18) than from preterm tissues (458 +/- 68.8 ng/mg DNA, n = 17). Spontaneous onset of labor, irrespective of the eventual mode of delivery, was not associated with any significant changes in IL-8 release from human gestational tissues compared to not-in-labor tissues, both at term and preterm. IL-8 release from gestational tissues was not significantly different in the absence or presence of chorioamnionitis. These data are in contrast to the previously reported stimulatory effects of bacterial endotoxin on IL-8 release from human gestational tissues. The data are consistent, however, with the suggestion that IL-8 release is an early event in chorioamnionitis that precedes the appearance of clinically overt symptoms.     

Increased circulating heat shock protein 70 levels in pregnant asthmatics

Asthma is one of the most common diseases complicating pregnancy and represents a risk factor for several maternal and perinatal complications. The natural history of asthma is known to change in pregnancy, but very few data are available in the terms of pathomechanism of this change during gestation. Circulating heat shock protein 70 (Hsp70) levels are decreased in healthy pregnancy, which might reflect physiological immunotolerance. The aim of our study was to determine the serum levels of Hsp70 in asthmatic women during gestation. Forty pregnant women with bronchial asthma and 40 healthy pregnant women matched for maternal and gestational age were involved in this case-control study. Serum Hsp70 levels were measured using the ELISA Kit of R&D Systems. Spirometry and oxygen saturation measurements were performed in asthmatic patients. In asthmatic pregnant women, an increase of serum Hsp70 levels was observed compared to healthy pregnant women (median (25–75 percentile): 0.44 ng/ml (0.36–0.53) versus 0.21 ng/ml (0–0.27), p < 0.001). Fetal birth weight of asthmatic mothers was significantly smaller than of healthy controls, but in the normal range (3,230 g (2,690–3,550) versus 3,550 g (3,450–3,775), p < 0.05). A statistically significant negative correlation between maternal age and serum Hsp70 concentrations (Spearman R = −0.48, p = 0.0018) and a significant positive correlation between gestational age and serum Hsp70 levels (Spearman R = 0.83, p < 0.001) were detected in healthy pregnant women. In conclusion, this study proves an elevation of circulating Hsp70 levels during asthmatic pregnancy compared to healthy pregnant women. However, further studies are warranted to determine the role of circulating Hsp70 in the pathogenesis of maternal and perinatal complications of asthma in pregnancy.     

Parturition prediction and timing of canine pregnancy

An accurate method of predicting the date of parturition in the bitch is clinically useful to minimize or prevent reproductive losses by timely intervention. Similarly, an accurate method of timing canine ovulation and gestation is critical for development of assisted reproductive technologies, e.g. estrous synchronization and embryo transfer. This review discusses present methods for accurately timing canine gestational age and outlines their use in clinical management of high-risk pregnancies and embryo transfer research.     

Factors Affecting Date of Implantation,Parturition, and Den Entry Estimated from Activity and Body Temperature in Free-Ranging Brown Bears

Knowledge of factors influencing the timing of reproduction is important for animal conservation and management. Brown bears (Ursus arctos) are able to vary the birth date of their cubs in response to their fat stores, but little information is available about the timing of implantation and parturition in free-ranging brown bears. Body temperature and activity of pregnant brown bears is higher during the gestation period than during the rest of hibernation and drops at parturition. We compared mean daily body temperature and activity levels of pregnant and nonpregnant females during preimplantation, gestation, and lactation. Additionally we tested whether age, litter size, primiparity, environmental conditions, and the start of hibernation influence the timing of parturition. The mean date of implantation was 1 December (SD = 12), the mean date of parturition was 26 January (SD = 12), and the mean duration of the gestation period was 56 days (SD = 2). The body temperature of pregnant females was higher during the gestation and lactation periods than that of nonpregnant bears. The body temperature of pregnant females decreased during the gestation period. Activity recordings were also used to determine the date of parturition. The parturition dates calculated with activity and body temperature data did not differ significantly and were the same in 50% of the females. Older females started hibernation earlier. The start of hibernation was earlier during years with favorable environmental conditions. Dates of parturition were later during years with good environmental conditions which was unexpected. We suggest that free-ranging pregnant brown bears in areas with high levels of human activities at the beginning of the denning period, as in our study area, might prioritize investing energy in early denning than in early parturition during years with favorable environmental conditions, as a strategy to prevent disturbances caused by human.     

Factors affecting foal birth weight in Thoroughbred horses

Foaling data from 348 Thoroughbred foals born on a commercial stud were analysed to investigate interrelationships among mare age, parity, gestation length, foal sex, placental weight, and foal birth weight. Placental weight was positively correlated with foal birth weight up to a threshold of 6.5 kg; above this, placental weight was not significantly associated with foal birth weight. Placental weight was assessed, including the amniotic membranes and umbilical cord as well as the allantochorion. Using path analysis, parity was positively associated with foal birth weight both directly and through increased placental weights, but age was not directly related to foal birth weight. Over the range of gestation lengths observed, gestation length was not significantly associated with foal birth weight. We conclude that, in populations represented by this study population, either placental weights up to 6.5 kg are rate-limiting for foal birth weight or placental weight increases with foal birth weight up to this threshold. However, further increases in placental weight are not associated with additional increases in foal birth weight. The positive association between parity and foal birth weight is mediated through increased placental weight as well as other pathways. Age is not directly related to foal birth weight and gestation length is not strongly associated with foal birth weight.     

Effect of Selenium Supplementation on Blood Status and Milk,Urine, and Fecal Excretion in Pregnant and Lactating Camel

Ten pregnant female camels divided into two groups received, after a 2-week adaptation period, an oral selenium (Se) supplementation (0 and 2 mg, respectively) under sodium selenite form for 6 months from the three last months of gestation up to the three first months of lactation. Feed intake was assessed daily. Blood samples and body weight were taken on a biweekly basis, both in dams and their camel calves after parturition. Feces and urine samples were collected monthly and milk on a biweekly basis. The Se concentration in serum increased significantly in the supplemented group and was threefold higher than the concentration compared to the control group, respectively, 305.9 ± 103.3 and 109.3 ± 33.1 ng/mL. The selenium concentration increased in similar proportion in milk (86.4 ± 39.1 ng/mL in the control group vs 167.1 ± 97.3 ng/mL in treated group), in urine, and feces. The gluthathione peroxidase (GSH-Px) activity varied between 18.1 ± 8.7 IU/g hemoglobin (Hb) in control group and 47.5 ± 25.6 IU/g Hb in treated group but decreased after parturition in both groups. Vitamin E did not change significantly and was, on average, 1.17 ± 0.72 and 1.14 ± 0.89 ng/mL in the control and treated groups, respectively. Significant correlations were reported between serum Se, milk Se, GSH-Px, and fecal and urinary excretion or concentration. Blood values in camel calves were similar to those of the dams. The results seemed to confirm the sensitivity of camel to Se supplementation with an important increase of selenium in serum and milk.     

microRNA expression in the cervix during pregnancy is associated with length of gestation

Preterm birth is a leading cause of infant mortality and can lead to poor life-long health and adverse neurodevelopmental outcomes. The pathophysiologic mechanisms that precede preterm labor remain elusive, and the role that epigenetic phenomena play is largely unstudied. The objective of this study was to assess the association between microRNA (miRNA) expression levels in cervical cells obtained from swabs collected during pregnancy and the length of gestation. We analyzed cervical samples obtained between 16 and 19 weeks of gestation from 53 women in a prospective cohort from Mexico City, and followed them until delivery. Cervical miRNA was extracted and expression was quantified using the NanoString nCounter Analysis System. Linear regression models were used to examine the association between miRNA expression levels and gestational age at delivery, adjusted for maternal age, education, parity, body mass index, smoke exposure, and inflammation assessed on a Papanicolaou smear. We identified 6 miRNAs that were significantly associated with gestational age at the time of delivery, including miR-21, 30e, 142, 148b, 29b, and 223. Notably, per each doubling in miR-21 expression, gestations were 0.9 (95% CI: 0.2–1.5) days shorter on average (P = 0.009). Per each doubling in miR-30e, 142, 148b, 29b, and 223 expression, gestations were shorter by 1.0 to 1.6 days. The predicted targets of the miRNAs were enriched for molecules involved in DNA replication and inflammatory processes. The levels of specific miRNAs in the human cervix during pregnancy are predictive of gestational age at delivery, and should be validated in future studies as potential biomarkers of preterm birth risk.Key words: Cervix, delivery, gestational age, labor, microRNA, Pap smear, preterm     

Ultrasonic measurements of second and third trimester fetuses to predict gestational age and date of parturition in captive and wild spotted hyenas Crocuta crocuta

Parturition in spotted hyenas (Crocuta crocuta) is a fascinating event to witness, as females of this species are highly masculinized and give birth through a penis-like clitoris. Furthermore, shortly after birth, a high rate of aggression occurs between littermates that can sometimes end in siblicide. To study these events thoroughly, an accurate estimate of the date of parturition is necessary. To this end, we performed transabdominal ultrasounds every 20-30 days in five captive spotted hyenas of known gestational age, beginning approximately 30 days after mating. We measured the femur length (FL), abdominal circumference (AC), and biparietal diameter (BPD) of eight fetuses from Days 42 to 100 of their 110 days of gestation. FL proved to be the most effective measurement, as it correlated well with gestational age and was easy to obtain consistently. The relationship between estimated gestational age (EGA) and FL is described by the equation: [EGA = 37.3 + (14.0 x FL)]. AC also correlated well with EGA, but was more difficult to measure than FL. Measuring BPD became increasingly difficult as pregnancies advanced beyond 70 days of gestation. Because gestational age is often not known in captive and free-ranging spotted hyenas, measuring fetal FL ultrasonographically is a rapid and reliable way to determine an approximate date of parturition. This technique proved invaluable when used to track and monitor a free-ranging spotted hyena during the days just before and after parturition.     

Worsening of neck and shoulder complaints in humans are correlated with frequency parameters of electromyogram recorded 1-year earlier

The aim was to investigate whether output and electromyogram (EMG) variables obtained from an isokinetic endurance test of the shoulder flexor muscles of 23 women with neck and shoulder problems in a car and truck industry correlated with improvement or worsening of complaints 1 year later. Each subject performed 100 maximal isokinetic shoulder forward flexions at 60° · s⁻¹. Surface EMG of the trapezius, deltoid, biceps brachii and infraspinatus muscles and mechanical output (peak torque) were determined for each contraction. The EMG was used to determine mean frequency f _mean and the ratio between the signal amplitudes of the EMG of the passive relaxation and active flexion parts of each contraction cycle (SAR). The subjects also rated the degree of fatigue they experienced throughout the test. The magnitude of the shift in f _mean was correlated with whether improvement or worsening occurred for complaints in the neck and or shoulders; a significant relationship (r ² = 0.44; P = 0.001) existed between the total frequency shift of the four muscles and the variables measuring improvement in complaints. In the multivariate predictions other f _mean variables and perception of fatigue were also of significance. The present study would indicate that a high degree of f _mean shift correlates with improvement in neck and shoulder complaints 1 year later. One possible reason could be that f _mean reflects the muscle morphology and/or a pathological situation for the type-1 muscle fibres. Accepted: 27 May 1998     

The influence of gestational age and onset of labour on determinants of fetal-maternal fluid and electrolyte balance in sheep.

Our aim was to compare the effects of gestational age and the timing of the onset of labour on factors influencing fetal fluid and electrolyte balance and urine production in fetal sheep. We measured the volume and composition of fetal urine and amniotic and allantoic fluids, as well as fetal and maternal plasma composition and micturition episodes in sheep during late gestation until the onset of labour. We found that daily fetal urine production and urethral urine flow per micturition episode increased significantly in relation to the onset of labour but not to gestational age (P < 0.05). In the 2 days preceding the onset of labour fetal urine and amniotic fluid K+ concentrations and urine osmolality increased significantly and the Na+/K+ ratio in allantoic fluid decreased significantly (P < 0.05). There was also a significant fall in fetal arterial SaO2 (P < 0.05) but no significant changes occurred in fetal plasma electrolyte composition, osmolality or AVP concentrations. Fetal plasma cortisol and prolactin concentrations and amniotic and allantoic fluid prolactin concentrations increased significantly and progressively in association with both advancing gestation and the onset of labour whereas maternal plasma prolactin concentrations increased significantly only in the 2 days before the onset of labour (P < 0.05). We conclude that some developmental aspects of fetal fluid and electrolyte balance, including renal function, are more closely related to the timing of parturition than to gestational age per se.     

Probing the stability of S-layer-supported planar lipid membranes

Isolated protein subunits of the crystalline bacterial cell surface layer (S-layer) of Bacillus coagulans E38-66 have been recrystallized on one side of planar black lipid membranes (BLMs) and their influence on the electrical properties, rupture kinetics and mechanical stability of the BLM was investigated. The effect on the boundary potential, the capacitance or the conductance of the membrane was negligible whereas the mechanical properties were considerably changed. The mechanical stability was characterized by applying voltage pulses or ramps to induce irreversible rupture. The amplitude of the voltage pulse leading to rupture allows conclusions on the ability of membranes to resist external forces. Surprisingly, these amplitudes were significantly lower for composite S-layer/lipid membranes compared to undecorated BLMs. In contrast, the delay time between the voltage pulse and the appearance of the initial defect was found to be drastically longer for the S-layer-supported lipid bilayer. Furthermore, the kinetics of the rupture process was recorded. Undecorated membranes show a fast linear increase of the pore conductance in time, indicating an inertia-limited defect growth. The attachment of an S-layer causes a slow exponential increase in the conductance during rupture, indicating a viscosity-determined widening of the pore. In addition, the mechanical properties on a longer time scale were investigated by applying a hydrostatic pressure across the BLMs. This causes the BLM to bulge, as monitored by an increase in capacitance. Compared to undecorated BLMs, a significantly higher pressure gradient has to be applied on the S-layer face of the composite BLMs to observe any change in capacitance. Received: 4 May 1999 / Revised version: 1 July 1999 / Accepted: 1 July 1999     

Maternal group B streptococcus infection, neonatal outcome and the role of preventive strategies

To determine the newborn infection rate with group B streptococcus infection (GBS) before and after American Academy of Pediatrics Protocol (AAP) implementation in Croatia, antenatal risk factors, neonatal outcome and necessity for introducing national policy for intrapartum chemoprophylaxis. To evaluate the role of intrapartum chemoprophylaxis in preterm labor at < 37 weeks of gestation, premature rupture of membranes at < 37 weeks of gestation, fever during labor, ruptures of membranes > 18 hours before delivery and previous delivery of a sibling with GBS disease. A total of 784 neonates admitted to the Neonatal Intensive Care Unit, from 1 January 2005 to 31 December 2005. 60 (10/1000 live born) developed early-onset infection (EOGBS). The dominant presentation for EOGBS was sepsis (65%), pneumonia (32.2%) and meningitis (3%). Mean gestational age was 34.5 (+/- 5.3) weeks. There were 2 neonatal deaths (3%) in EOGBS, both preterm. EOGBS disease was associated with following risk factors: rupture of the membranes > 12 hours (49.3%), chorioamnionitis (11.9%), status post cerclage (10.4%), diabetes mellitus (4.5%), delivery out of hospital (3%), uroinfection (1.5%). After AAP implementation the incidence of GBS infection decreased from 15/1000 to 10/1000 of live born infants. The mortality from EOGBS dropped from 5% to 3%. The incidence of GBS infection in our study was considerably higher than in all current reports. Reasons for that can be inadequate perinatal screen in some parts of the country and no established policy for intrapartum antibiotic treatment of women with risk factors. Our results documented that intrapartum chemo-prophylaxis for GBS infection significantly reduces perinatal mortality due to neonatal infection and sepsis.     

女性生殖道解脲支原体感染与胎膜早破与新生儿窒息的相关性

摘要 目的：探讨女性生殖道解脲支原体(Ureaplasma urealyticum,UU)感染与胎膜早破与新生儿窒息的相关性。方法：2017年6月至2019年6月选择在地区门诊就诊的孕妇108例,检测生殖道解脲支原体感染情况,调查所有孕妇的一般资料、分娩方式、胎膜早破、新生儿窒息状况并进行相关性分析。结果：在108例孕妇中,48例检出解脲支原体感染,感染率为44.4 %。感染组的年龄、体重指数、产次、孕次、受教育年限、孕周等与非感染组对比差异无统计学意义(P>0.05)。感染组的胎膜早破与新生儿窒息发生率分别为22.9 %和18.8 %,显著高于非感染组的3.3 %和1.7 %(P<0.05)。感染组的剖宫产率高于非感染组,自然分娩率低于非感染组,对比差异都有统计学意义(P<0.05)。在108例孕妇中,Pearson分析显示解脲支原体感染与胎膜早破、新生儿窒息都存在相关性(P<0.05)。结论：女性生殖道解脲支原体感染比较常见,可导致剖宫产、胎膜早破、新生儿窒息发生率增加,也与胎膜早破、新生儿窒息存在显著相关性。     

Real-time ultrasound measure of the fetal eye (vitreous body) for prediction of parturition date in small ponies

Ultrasonographic fetal eye measures have been used to estimate gestational age of the fetus in light horse mares. However, fetal eye measures have not been published for smaller pony breeds. This study was conducted to develop reference ranges for ultrasonographic measures of fetal eyes in small ponies for the purpose of predicting days before parturition (DBP) when breeding or ovulation dates are unknown. Twenty-three Shetland-type pony mares were studied across one (n = 10) or two (n = 13) gestations in 2004 (18 pregnancies) and 2005 (18 pregnancies). Measurements of fetal eyes were obtained during transrectal ultrasound examination. Examinations were conducted once monthly in a field situation beginning in December (2003) or August (2004) until mares foaled (March through July). The length (from sclera to sclera) and width (from retina to cornea) of the vitreous body were measured. For the 273 examinations in which gestation age was greater than 2 months, eye measures were obtainable in 248 (91%). Mixed-effects linear regression modeling was used to account for serial growth measures within pregnancy, repeated measurements across mares, and unbalanced study design. Independent variables evaluated included vitreous body length, vitreous body width, the ratio of length to width, parity, and mare height at the withers at parturition. Eye length was the best single predictor of days before parturition, with almost no additional predictive value of the other variables considered. Our resulting regression equation is: days before parturition=265.16-0.21*(vitreous body length in mm)(2). This study suggests that measure of the fetal eye is a practical on-farm procedure for estimating days before parturition in small ponies.     

The response of sap flow to pulses of rain in a temperate Australian woodland

In water-limited systems, pulses of rainfall can trigger a cascade of plant physiological responses. However, the timing and size of the physiological response can vary depending on plant and environmental characteristics, such as rooting depth, plant size, rainfall amount, or antecedent soil moisture. We investigated the influence of pulses of rainfall on the response of sap flow of two dominant evergreen tree species, Eucalyptus crebra (a broadleaf) and Callitris glaucophylla (a needle leaved tree), in a remnant open woodland in eastern Australia. Sap flow data were collected using heat-pulse sensors installed in six trees of each species over a 2 year period which encompassed the tail-end of a widespread drought. Our objectives were to estimate the magnitude that a rainfall pulse had to exceed to increase tree water use (i.e., define the threshold response), and to determine how tree and environmental factors influenced the increase in tree water use following a rainfall pulse. We used data filtering techniques to isolate rainfall pulses, and analysed the resulting data with multivariate statistical analysis. We found that rainfall pulses less than 20 mm did not significantly increase tree water use (P > 0.05). Using partial regression analysis to hold all other variables constant, we determined that the size of the rain event (P < 0.05, R ² = 0.59), antecedent soil moisture (P < 0.05, R ² = 0.29), and tree size (DBH, cm, P < 0.05, R ² = 0.15), all significantly affected the response to rainfall. Our results suggest that the conceptual Threshold-Delay model describing physiological responses to rainfall pulses could be modified to include these factors. We further conclude that modelling of stand water use over an annual cycle could be improved by incorporating the T-D behaviour of tree transpiration. Responsible Editor: Stephen S.O. Burgess     

Glycogen metabolism in human fetal testes

The ontogeny of glycogen synthetase, glycogen Phosphorylase and α-D-glucosidase, enzymes which are associated with glycogen metabolism and glycogen level has been studied in human fetal testes of gestational age ranging from 14–32 weeks. Glycogen synthetase activity reaches the peak value at 17–20 weeks of gestation, thereafter it decreases. α-D-Glucosidase activity increases with the advancement of pregnancy up to 28 weeks of gestation decreasing thereafter very rapidly. Phosphorylase activity remains more or less constant throughout gestation. The maximum increase in glycogen content at early stages of gestation (17–20 weeks) and gradual reduction with the advancement of pregnancy are correlated with histochemical observation by the periodic acid-Schiff technique.     

Prostaglandin biosynthesis stimulatory and inhibitory substances in human amniotic fluid during pregnancy and labor

Human amniotic fluid has been separated into two fractions; one fraction inhibits prostaglandin biosynthesis and the other fraction is stimulatory. The activity of the stimulatory fraction increased with increasing gestational age and was greater still during labor. The activity of the inhibitory fraction decreased with increasing gestational age and was smaller still during labor. We speculate that these changes may play a significant role in parturition.