. >> california watch reporter nathaniel johnson poured over the records and found significant differences rates have been climbing for years partly because of older mothers and increasing obesity. johnson took out the highest risk for analysis. >> we found a healthy woman walking into at hospital, if its for profit hospital, she has a greater chance of having a c-section. >> in fact 15% more likely. they were found in hospitals catering to all ethnic groups and. >> there were lots of examples of hospitals in the same area serving the same population with radically different rates. >> some of it may be patient characteristics but it could be hospital, physician characteristics. >> he chair of obstetrics and gynecology in san francisco. its private hospital. >> its difficult business. we can be damned for doing too few c-sections and damned if we too many. >> the rate was lower than the statewide average for similar hospitals. >> many of the public hospitals are teaching hospitals and have more standardized approach to care. in a private hospital there is a lot more independence of the phys

that is a finding of nathaniel johnson of california report. >> the normal length of pregnancy is 40 weeks. according to researchers the average is now 39 weeks, a full seven days earlier. >> what they just found is undoubtedly true that there is a decrease in the average age. >> he is also director of the california of california collaborative. they evaluate best practices for delivering babies. a full term pregnancy is defined as 39 to 41 weeks. the week of pregnancy lost is not having an impact on the health of most infants. >> what we are telling most mothers you ought to wait 39 weeks if everything is going fine and not intervene. >> one reason may be because more women are scheduling childbirth for convenience. one study of nearly 18,000 deliveries in 2007 showed 9.6% of early births were scheduled c-sections. others may be simply a matter of better care. >> we're doing a much better job of identifying with ultrasounds. we no longer of mothers going past their due date. >> a number of groups are encouraging people not to deliver babies early. >> the interesting thing this is so

that is the finding of california watch reporter nathaniel johnson. >> it's pretty much been the sameormal length is 40 weeks, according to researchers and data compiled at cdc, the average is 39 weeks, a full seven days earlier. >> what they just found is undoubtedly true that there is a decrease in the average age of birth in america. >> he is a director of california maternal care collaborative a group that evaluates best practices for delivering babies. he says a full term pregnancy is defined as 39 to 41 weeks. he believes the week lost in the last 20 years is probably not having a significant impact on the health of most infants. >> what we are telling all of our mothers, you really ought to wait 39 weeks, if everything is going fine, and not intervene. >> would reason for the increase in early dloovs may be because more women are scheduling childbirth for convenience. one study of nearly 18,000 deliveries showed 9.6% were scheduled c-sections. that may explain some of the early deliveries and others may be better care. >> we're doing a much better job of identifying the true du

that's the finding of california watch reporter nathaniel johnson. >> from 10,000 bc to 1992, it's pretty same. >> the normal length of a pregnancy is 40 weeks. according to researchers and data compiled at the centers for disease control and prevention, the average is now 39 weeks, a full seven days earlier. >> what data found is undoubtedly true, that there is a decrease, a general decrease in the average birth in america. >> dr. elliot is at the california pacific medical center in san francisco. he's also director of the california maternal care collaborative, a group that evaluating best practices for delivering babies. the best is 39 to 41 weeks. he believes the week of pregnancy lost in the last 20 years is probably not having a significant impact on the health of most infants. >> what we are telling all our mothers is that you really ought to wait the 39 weeks if everything is going fine and not intervene earlier than nature would intend. >> one reason for the increase in early delivers, may be because more women are actually scheduling childbirth for convenience. one study of nea

that's the finding of california watch reporter nathaniel johnson. >> 10,000 bc to 1992 it's pretty muchn the same. >> the normal length of a pregnancy is 40 weeks. according to researchers and the data compiled at center for disease control and prevention, the average is 39 weeks, a full seven days earlier. >> it's undoubtedly true, that there is a decrease, a general decrease to birth in america. >> dr. elliot is at the california medical in san francisco. he's the director of the california maternal care collaborative, a group that evaluating best practices for delivering babies. he says a full-time pregnancy is defined at 39 to 41 weeks. the week of pregnancy lost in the last 20 years is probably not having a significant impact on the health of most infants. >> what we are telling all our mothers is that you really ought to wait till 39 weeks if everything is going fine and not intervene earlier than nature would intend. >> one increase in early delivers may be because women are scheduling childbirth for convenience. one study of nearly 18,000 delivers in 2007 show 19.6% of early bir

that's the finding of california watch reporter nathaniel johnson. >> from 10,000 bc to 1992 it's pretty norm birth is 40 weeks. the average now 39 weeks, a full seven days earlier. >> it's undoubtedly true that there is a general decrease in the average age of birth in america. >> dr. elliot is chairman of gynecology in san francisco, also director of the california maternal care collaborative that evaluating best practices of delivering babies. he says a full term pregnancy is 39 to 41 weeks. the week of pregnancy lost in the last 20 years is probably not having a significant impact on the health of most infants. >> what we are telling all our mothers is that you really ought to wait the 39 weeks if everything is going fine and not intervene earlier than nature would intend. >> one reason for the increase in early delivers may be because more women are actually scheduling childbirth for convenience. one study of nearly 18,000 delivers in 2007 showed 9.6% of early births were scheduled c-sections. the doctor said that may explain some of the early delivers. others may be simply a matter