Women appear more likely to repeatedly give birth through Caesarean section if they have their babies in teaching and non-profit hospitals and if they do not have medical insurance, researchers reported.

A study published Tuesday involving 45,425 births among California women found non-medical factors appeared to play an important role in determining whether women underwent repeated Caesarean sections.Caesarean sections involve surgically removing the baby from the womb rather than delivering the child naturally through the vagina. The procedure is designed for when problems develop during delivery that threaten the mother or child.

About 967,000 Caesarean sections were performed in the United States in 1988, accounting for about a quarter of all births. The rate has quadrupled in the United States in the past two decades.

In the new study, published in the Journal of the American Medical Association, Randall Stafford of the University of California-Berkeley and his colleagues examined the relationship between various factors and Caesarean sections.

The researchers found that less than 5 percent of women giving birth in for-profit hospitals after having had one Caesarean section had another Caesarean section, compared to more than 29 percent at non-profit hospitals.