Obstetricians consider women over age 35 to be of "advanced maternal age." But more women over age 35 are getting pregnant---one in five first time new moms is over 35, the March of Dimes states. While it's still quite possible to get pregnant over 35, pregnancy complications are more common in older moms.
Higher Miscarriage Rate
More women over age 35 have miscarriages in early pregnancy, because the remaining eggs of older women are more likely to have abnormal chromosomes. Women are born with all the eggs they'll ever have; new eggs are not continually produced like sperm are. Women around age 25 have a miscarriage rate of around 10 percent after pregnancy is confirmed; for women age 35, the rate is around 20 percent, increasing to 35 percent by age 40, and may be as high as 50 percent at age 45. This increase in miscarriage is related, at least in part, to the increase in chromosomally abnormal eggs as women age, the March of Dimes says. At least half of all first trimester miscarriages are related to chromosomal abnormalities, according to the University of Virginia.
Chromosomal Abnormalities
Women over age 35 are more likely to have a child with chromosomal abnormalities like Down syndrome and other trisomies, genetic defects where three copies of a gene are present instead of the normal two. The average 25 year old has a one in 2,500 chance of having a child with Down syndrome; at age 35, the odds are one in 400. By age 40, the risk is one in 100, and at age 45, one in 30, according to the University of Virginia. The rate for any chromosomal abnormality at age 25 is one in 385 and one in 178 at age 35. The risk increases to one in 63 at age 40 and one in 18 at age 45, the University of Virginia reports.
Gestational Diabetes
Women over age 35 are about twice as likely to develop gestational diabetes, high blood sugar that develops during pregnancy and disappears after delivery. Gestational diabetes increases the risk of macrosomia, or large babies. Macrosomic infants can have traumatic injuries from the birth, often have breathing problems and don't feed well. Macrosomia also increases the risk of cesarean delivery.
Placental Problems
The placenta is the lifeline for nutrients and oxygen to the fetus. Anything that disturbs the placenta can result in decreased oxygen and nutrients to the growing fetus. Women in their late 30 are twice as likely to have a placenta previa, a placenta that implants too low on the uterine wall and completely or partially covers the cervix. Women in their 40s have a threefold risk. Severe bleeding can occur, threatening the lives of mother and baby.
Preterm Delivery and Stillbirth
Prematurity is slightly more common in older mothers. Stillbirth, the death of the fetus before birth, is two to three times as common in women over age 40, for reasons not fully understood, according to the March of Dimes.
Increased Cesarean Sections
Women over 40 have a higher rate of cesarean delivery; the rate of cesarean delivery over age 40 is around 47 percent, compared to 27 percent for women in their early 20s.
