A new study found that for mothers who wait less than 18 months to become pregnant again the ensuing pregnancy is shorter. Published in BJOG: An International Journal of Obstetrics and Gynaecology the study examined interpregnancy intervals (IPIs) from 454716 live births of mothers who experienced two or more pregnancies over a period of six years. Subjects were divided into three categories according to their IPIs. The shortest IPI category consisted of those under 12 months next came 12 to 18 months and finally an IPI of over 18 months considered by the researchers to be optimal. Results concluded that