***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Midtrimester amniocentesis to investigate fetal karyotype carries a small risk of fetal loss . AIM To test the hypothesis that progesterone prophylaxis may reduce this . STUDY DESIGN A r and omised controlled trial comparing a short prophylactic treatment with progesterone after amniocentesis with untreated controls . RESULTS There were no differences in frequency of miscarriage , preterm delivery or neonatal outcome . CONCLUSION Prophylactic progesterone treatment after amniocentesis does not improve obstetric outcome A prior report suggested that active-duty pregnant women are at increased risk for low-birth weight infants and a higher perinatal mortality rate . The present double-blind investigation was design ed to prospect ively evaluate that risk and to test the efficacy of 17 alpha-hydroxyprogesterone caproate to prevent reported complications . Three groups of active-duty women were studied , beginning between 16 and 20 weeks ' gestation . They were similar for parity , previous abortion , race , cigarette smoking , and marital status . Of these , 80 were given 17 alpha-hydroxyprogesterone caproate , 88 received placebo , and 78 declined to participate in the protocol . There was no significant differences in the three groups when comparisons were made for low-birth weight infants and for perinatal mortality . However , when comparison was made to a military dependent population , they had a significantly worse outcome with regard to both perinatal mortality ( p = 0.001 ) and infants with a birth weight less than 2,500 gm ( p = 0.01 ) . We concluded that pregnant military personnel were at increased risk for adverse pregnancy outcome , but that this risk was not altered by therapy with 17 alpha-hydroxyprogesterone caproate OBJECTIVE The purpose of this study was to evaluate the effect of prophylactic vaginal progesterone in decreasing preterm birth rate in a high-risk population . STUDY DESIGN A r and omized , double-blind , placebo-controlled study included 142 high-risk singleton pregnancies .  Progesterone ( 100 mg ) or placebo was administered daily by vaginal suppository and all patients underwent uterine contraction monitoring with an external tocodynamometer once a week for 60 minutes , between 24 and 34 weeks of gestation . Progesterone ( n = 72 ) and placebo ( n = 70 ) groups were compared for epidemiologic characteristics , uterine contraction frequency , and incidence of preterm birth . Data were compared by chi(2 ) analysis and Fisher exact test . RESULTS The preterm birth rate was 21.1 % ( 30/142 ) . Differences in uterine activity were found between the progesterone and placebo groups ( 23.6 % vs 54.3 % , respectively ; P < .05 ) and in preterm birth between progesterone and placebo ( 13.8 % vs 28.5 % , respectively ; P < .05 ) . More women were delivered before 34 weeks in the placebo group ( 18.5 % ) than in the progesterone group ( 2.7 % ) ( P < .05 ) . CONCLUSION Prophylactic vaginal progesterone reduced the frequency of uterine contractions and the rate of preterm delivery in women at high risk for prematurity Patients with multiple gestations or recalcitrant preterm labor are at very high risk for preterm birth in spite of adequate tocolysis . Subcutaneous infusion of tocolytic medications on an ambulatory basis has been used in several small series and has effectively prolonged gestation . This retrospective analysis presents data from 992 patients at very high risk for preterm delivery who were prescribed this therapy . The amount of tocolytic medication was individualized by utilizing the patient 's volume of distribution and clearance . Pharmacists adjusted the dosage based on uterine activity strips received by nursing personnel . The average basal rate was .073 + /- .020 mg/h . Patients received an average of seven scheduled boluses per day and 1.54 + /- .93 unscheduled boluses per week ( .25 + /- .03 mg each ) . The therapy extended the gestation a mean of 38 + /- 23 days and average gestational age at delivery was 36.3 + /- 2.6 weeks with a mean birthweight of 2759 + /- 681 g. This study , utilizing a large number of patients , confirms earlier reports that for women at very high risk for preterm delivery subcutaneous tocolytic infusion therapy is beneficial . Prospect i ve studies evaluating such treatment on a r and omized basis are indicated The potential tocolytic effect of natural progesterone administration on premature  labor  was investigated in a double-blind study . An oral progesterone formulation was used because its ability to increase both plasma and myometrial concentration of progesterone in pregnant women had been previously demonstrated . Furthermore , no commercial intravenous or intramuscular natural progesterone formulation is currently available in France . Fifty-seven patients in two obstetric clinics , admitted because of the risk of premature delivery , were included in the study , and uterine contractility and fetal cardiac rhythm were monitored in all of them . At r and om and after 30 minutes ' rest , 29 women absorbed four capsules of 100 mg of progesterone each and 28 women absorbed four capsules of a placebo .  Plasma progesterone levels were evaluated in all cases after 30 minutes ' rest and 1 hour after absorption of the capsules . The results showed that bed rest and placebo administration decrease uterine activity in 42 % of the cases and oral progesterone decreases activity in 75 % to 88 % of cases , depending on the initial severity of the menace of premature delivery . The difference between the effects of progesterone and of placebo is significant . The tocolytic effect of oral progesterone is not as intense or as rapid as the effect of intravenous beta-mimetics but is sufficient in 80 % of cases , on the average , to stop the premature labor without any detectable side effects . This tocolytic effect of oral progesterone is related not just to an increase in plasma progesterone levels but probably to an increase in myometrial progesterone concentration There are indications that prophylactic administration of 17α-hydroxyprogesterone caproate ( 17α-OHP-C ) could be beneficial in the treatment of women at risk for preterm delivery . Since twin pregnancy is commonly associated with prematurity , 77 women with twin pregnancy were treated during the last trimester until the 37th gestational week with weekly injections of either 17α-OHP-C or a placebo , following double-blind principles . The gestational length and birth weight and the outcome of the neonates were similar in both groups . The administration of 17α-OHP-C thus seems ineffective in the prevention of prematurity risks associated with twin pregnancy .  ( Obstet Gynecol 56:692 , 1980 The results of a study concerning the treatment of acute menace of preterm labor are given : beta-mimetics were administered intravenously in all cases ( 44 ) and micronized progesterone or placebo was administered orally after classical double-blind r and omization ( 22 cases in each group ) . The mean index of pregnancy prolongation was the same in both groups . However the mean duration of the intravenous perfusion and the mean quantity of beta-mimetics administered intravenously were significantly reduced in the progesterone group ( P less than 0.01 ) . The mean duration of hospital stay was also significantly reduced ( P less than 0.05 ) . Cost and risks are finally significantly lessened 
    Output:
    
No differences in rates of hospital admissions for threatened preterm labor or perinatal mortality were noted for subjects receiving progestational agents in general or for those receiving only 17α-hydroxyprogesterone caproate specifically .
: The use of progestational agents and 17α-hydroxyprogesterone caproate reduced the incidence of preterm birth and low birth weight newborns