Have gestational diabetes.
In 2000, the incidence was 69.5 per 1,000 for women over 40 compared to 8.8 per 1,000 for women under 20. The average incidence was 29.3 per 1,000 women.

Have pregnancy-associated hypertension.
In 2000, the incidence ranged from 40 to 48 per 1,000 for women over 40. The average incidence was 38.8 per 1,000 women.

Give birth to a low birth weight baby, defined as less than 2,500 grams.
Much of this risk results from the frequent multiple births among older women. In 2000, 55 percent of low birth-weight babies born to women over 45 were born in multiple deliveries. If only singleton births are considered, women over 45 were substantially less likely to have a low birth-weight baby than the youngest women.

Have amniocentesis.
In 2000, 19.4 per 1,000 women age 30 to 34 had the procedure, while 95.9 per 1,000 women age 35 to 39 opted for it.

Miscarry.
Miscarriage rates for women in their 30s increase by about 50 percent over women in their 20s and increase twofold to fourfold for women in their 40s. Almost half of all pregnancies to women over 40 may be lost to miscarriage.

Have complications of labor and delivery.
In 2000, placental abruption occurred in 5.1 pregnancies per 1,000 for women 25 to 29 and in 8.0 pregnancies per 1,000 for women 40 to 54. Breech births occurred in 38.2 births per 1,000 for women 25 to 29 and in 57.4 births per 1,000 for women 40 to 54.

Sustain late fetal death before delivery.
Stillbirth and late-term fetal death are more likely to happen to women over 40, to women with hypertension, and to babies with genetic abnormalities.

Give birth to a child with Down's syndrome.
This most common congenital abnormality is strongly associated with increased maternal age. In 2000, 24.8 births per 100,000 to women 20 to 24 were babies with Down's; 107.9 births per 100,000 to women 35 to 39 were babies with Down's; and 376.5 births per 100,000 to women 40 to 54 were babies with Down's.

Breast-feed.
Studies conducted in Britain and the United States show that older first-time mothers are more likely to breast-feed following birth and to continue breast-feeding.

Be well educated.
A number of studies find that older first-time mothers tend to be highly educated and working in a profession.

Have deliberately delayed child-bearing.
A 1992 study of older mothers ([ital] Birth [end ital], 1992, vol. 19, no. 1) reported that each additional year of postsecondary education delayed a woman's first birth by nine months.

Have younger partners.
A British study of first-time mothers over 40 found that their partners were on average three years younger than the women.

Have children with a high IQ.
Children's intellectual development has been positively linked to raised maternal age. Researchers have suggested that this correlation is not due to increased age, per se, but is a by-product of the increased attention given to children by older first-time mothers and their tendency to encourage verbalization and independence in their children.

Chart sources: Centers for Disease Control and Prevention; Older Mothers by Julia Berryman, et al. (Rivers Oram Publishing, 1999).