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近年美国的人口出生率持续走低FertilityratesintheUnitedStatesarecontinuingtheirdecades-longdecline,dueinlargeparttoasteepslideinteenagepregnanciesdowntohistoriclows,accordingtoanewgovernmentreportreleasedrecently.美国政府近期发布的工作报告指出，美国的人口出生率几十年来持续走低，很大程度上是由于青少年怀孕率大幅下滑至历史新低的缘故。TheNationalCenterforHealthStatisticssaidthepregnancyrateof102pregnanciesoutofevery1,000womenis12percentbelowthe1990peakofabout116per1,000.Onlyonceinthepast30years,1997,hasitbeenlower,andonlymarginally,thecentersaid.Since1990,thereportsaid,pregnancyratesaredowninalmosteverycategory.Theonlyexceptionisamongwomenover30,whosepregnancyratehasincreasedsteadilywitheverypassingyear.Buttherateisdecliningamongwomenintheir20s,whoformthesinglelargestgroupofpregnantwomen,andamongteenagersofallracesandethnicities.Theabortionratealsohasdropped,reflectingacontinuousslidesincepeakingin1990.Thereportonlyexaminedthetrajectoryofpregnancyratesthrough2009,stoppingtherebecausemorerecentdataonabortionsisnotavailableyet.Butnewerstatisticsonbirthratessuggestthedeclineiscontinuing,thoughnotasquicklyasitdidinrecentyearswhentherecessionacceleratedtrendswellunderway.Womenalreadywerehavingfewerchildrenthanwomenoftheirparents'andgrandparents'generations,sothoseunder30couldpostponechildbirthuntiltheeconomyimprovedwithoutaffectingtheirlongstandinggoalsofhavingafirstorsecondchild."Whathappenedwasapostponementofbirthsamongyoungerwomenwithalongertimehorizon,"saidAndrewCherlin,aJohnsHopkinsUniversitysociologistspecializinginfamilyissues."Womenover30couldn'twaitthatmuchlonger."Whilethedeceleratingdeclineinbirthratessince2009reflectstheeasingoftherecession'simpact,thestrikingdropinteenagepregnanciesshowslittlesignofabating.Theteenpregnancyratein2009,ofabout38perthousandgirls,was39percentlowerthanthe1991peakof62.Justfouryearslater,in2012,itreachedarecordlowofabout29.SallyCurtin,oneofthereport'sauthors,saidthehistoricdropisbeingdrivenbyalong,downwardtrendoffewerteenagershavingsex,andamongthosewhodo,asharpincreaseintheiruseofcontrac
