A study of older new mothers in Israel finds that 8 in 10 experienced health problems during their pregnancies, and nearly half of their babies were smaller than average.

First-time births over age 45 have more than tripled over the last decade in Israel. Though they still represent a small fraction of all births, the researchers note that the study highlights a downside to using assisted reproduction technologies to make first-time motherhood possible later and later in life.

The researchers gathered data on 131 mothers ranging in age from 45 to 65, who gave birth at the same hospital in Israel between 2004 and 2008.

Four of every 10 women developed pregnancy-related diabetes, and two of 10 had preeclampsia, a potentially dangerous condition that includes high blood pressure and protein in the mother's urine.

One third of the babies were born prematurely, and nearly all were delivered by a cesarean section.

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"This study shows that pregnancy after the age of 45 is in fact a risky proposition, and this provides a basis upon which women of this age group can be counseled" about those risks, said Dr. Richard Paulson, director of the in vitro fertilization program at the University of Southern California, who was not involved in the study.

In the U.S., first-time births to mothers over 45 still make up a very small percentage of all deliveries. In 2010, they totaled 2,028, with just 165 of those babies born to new mothers aged 50 and up, according to the Centers for Disease Control and Prevention.

In the Israeli study, the risk of having a baby born early or underweight was higher for women over age 50, than for women in their late 40s.

Two out of every three babies born to the mothers aged 50 to 65 weighed less than 2,500 grams (about 5 and a half pounds), and half were born prematurely. That compared to one out of three babies born either underweight, or prematurely, or both to mothers 45 to 49.

The study, published in the journal Fertility and Sterility, did not compare the women to mothers less than 45 years old, but the authors write that other studies have found much lower rates of pregnancy-related health problems and premature births in younger mothers.

All of the women in this study had experienced fertility problems and more than half had been pregnant before. All but five of the 131 women underwent in vitro fertilization (IVF), in which a fertilized egg is implanted into the mother's uterus.

Nearly a third of the women had a chronic disease like high blood pressure or diabetes before they got pregnant.

Paulson told Reuters Health that there is no policy dictating how old a mother can be to undergo IVF, although his clinic's policy is that women over age 50 who already have health problems are not candidates for the procedure.

Interestingly, the mothers over age 50 were more likely to have a boy than the mothers in their late 40s.

"There's no reason for that," Paulson said. "It just shows you that statistically significant results can sometimes happen by chance."

The health risks for older mothers are well established, however.

Paulson said that the way to mitigate those risks is to consider alternative procedures.

Women might consider "gestational surrogacy," in which another woman carries the child, but the father's sperm and sometimes the mother's egg are used to create the embryo.

Paulson also said that starting motherhood at an advanced age may carry risks, "but they're not prohibitive risks. People of all ages are interested in having a child and completing their families."
The study did not look at the excess cost of having a baby at an advanced age.