Factors that increase maternal health risks include high parity, short interpregnancy intervals, and pregnancy at both extremes of reproductive life.  In some countries, chronic malnutrition, excessive work, infectious diseases, poor environmental conditions, and inadequate medical care are added risks.  In these countries, death rates associated with childbearing are as high as 740/100,000 live births.  This is almost 50 times as high as in developed countries.  About 40% of women in developing countries have 4 or more children because they lack the knowledge or means to control their reproduction.  About 70% of those questioned stated that they wanted to limit the size of their families.  Only about 20% of rural populations have access to modern health services.  Many throughout the world turn to illegal abortion.  It is considered that the magnitude of maternal health problems in rural areas has been underestimated.  Until women have total reproductive freedom they cannot significantly improve their status.  For this reason family planning programs should permit adequate spacing between births and number of children born.   The optimal childbearing years are between the ages or 20 and 30.  In the U.S., the death rate from pregnancy and childbirth increases 10-12% for each year the mother is past the optimum age.   The shorter the birth interval, the greater the risk of mortality for both mother and child.  Also, high parity contributes to high maternal and infant mortality even in developed countries.  The decline in prolonged breast-feeding and lack of availability of effective contraceptives contribute to short birth intervals.   In some developing countries the death rate for women during their reproductive years is higher than for men of the same age.  This increased mortality results primarily from complications and of pregnancy and childbearing.  Physiological changes in pregnant women anticipate the needs of the developing fetus.   Nutritional needs are therefore increased.  After delivery, the mother's body needs at least 2 years and adequate nutrition to fully recuperate.  Nutritional anemia, vitamin deficiencies, and endemic goiter may follow frequent pregnancies.  Protein and iron deficiencies are especially common.  Inadequate diet, infections, and other dieseases contribute to these conditions.  Food taboos and weight-reducing regimens may add difficulties to proper nutrition.  Malaria and worm infestation in some countries are added complications.  Oral contraceptives, by reducing menstrual bleeding, reduce iron loss.  Some also contain an iron compound.  Although parity aggravates existing diabetes and may cause temporary biochemical evidence during pregnancy, more often than others develop diabetes in later years.  Most studies have not related cervical cancer to parity.