Midlife maternity

Pregnancy beyond the age of 35 poses risks for mother and child

Sixty might be the new 40, but attitude and medical advances can take you only so far before Mother Nature has her way.

That's the unfortunate reality for the growing number of women today who want to become pregnant at an advanced maternal age. Many older moms have uneventful pregnancies and perfectly healthy babies. There are important factors to consider, however, when deciding to become pregnant beyond the age of 35 – factors that include pronounced health risks for mom and baby.

The first potential obstacle that older would be moms must face is a doozy: they might not be able to become pregnant in the first place.

"My greatest concern for a woman at 35 is whether she can achieve pregnancy or not," says Oglesby Young, MD, an obstetrician, gynecologist and infertility specialist at Concord Obstetrics and Gynecology and at Concord Hospital, and adjunct assistant professor of obstetrics and gynecology at Dartmouth Medical School. Fertility in women drops off starting at the age of 30 and nosedives from about 40 on, he says, with only half of women that age remaining fertile.

Most often, age-related infertility is caused by the woman's eggs, which go through a process of selection during ovulation cycles. Throughout the childbearing years, a woman's "best" follicles, or egg-carrying sacs, become available for fertilization, with eggs that are less and less ideal left behind as the woman ages.

"A lot of women have the impression because of all of our assisted reproduction technologies today … that they can get pregnant any time they want, but unfortunately, that's not true," Young says. "Ovaries have a biologic clock; they don't allow that."

Assuming that an older woman who wants to have a child can become pregnant, she will still have more to worry about than a younger expectant mother would, including a greater chance of miscarriage.

Many women believe that a miscarriage is triggered by something they did or did not do, "but that's not true," Young says. "Miscarriages are abnormal pregnancies primarily because of the wrong number of chromosomes, and that is going to happen more often the older a woman gets."

If chromosome abnormalities are present in a pregnancy that does survive to term, the likely outcome will be a Down syndrome baby. At age 40, the risk of having a baby with Down syndrome is 1 in 100, and at 44 years old, it's about 1 in 40, Young says, compared with a 25-yearold's risk of 1 in 1,200.

Another problem whose incidence rises along with maternal age is ectopic pregnancy. An ectopic or tubular pregnancy occurs when the egg implants itself outside of the uterus. The odds of that happening in a woman who is 35 or 40 years old can climb as high as 1 in 50, Young says. An ectopic pregnancy is a non-viable pregnancy that can be lifethreatening to the mother, and it must be treated either medically or surgically.

Yet another risk that can be influenced by maternal age is the chance of twins. The correlation might seem counterintuitive since young women are typically more fertile than older women, but it happens because as a woman approaches 35 or 40, she's much more likely to ovulate twice in one cycle, Young says. A twin pregnancy by itself is a high-risk pregnancy.

"The uterus really was designed to carry one baby at a time, not two," he says. Other problems can lurk, too, for older pregnant women, simply because the older a person is, the more likely she is to have chronic medical conditions, Young says. Gestational diabetes, for example, one of the most widespread medical complications of mid-life pregnancy, occurs more often in older expectant moms because those women are more likely than their younger counterparts to have diabetes even before they become pregnant.

Likewise, some older moms suffer from systemic lupus, or kidney or cardiovascular problems. Forty-year-olds are more likely to be overweight than 20-year-olds, to be long-term smokers and to suffer from chronic hypertension, any of which predisposes them to a problematic pregnancy. Chronic hypertension "is probably the most common medical problem differentiating young pregnant women from older," Young says, and increases the likelihood of a number of serious pregnancy complications.

However, a healthy 40-year-old woman who has followed a good, balanced diet during her lifetime, begins pregnancy at a healthy weight, has not abused alcohol or smoked, and takes prenatal vitamins and gets regular prenatal care is a different story. Chances are, "she's going to have a healthy pregnancy, a healthy labor, a healthy delivery and a healthy baby," Young says.

In general, "if you've got a woman who has been taking good care of herself, she's going to do well with her pregnancy – as long as she can achieve that pregnancy," he says.

Screening tests can rule out potential trouble for older moms even before a pregnancy exists by looking for genetic markers of cystic fibrosis and other diseases, and other tests can be administered as a pregnancy progresses, Young says. Ultrasound and a blood test during pregnancy can check for Down's syndrome, for example, as can direct chromosomal testing, which involves analysis of a small piece of the placenta at 10 to 12 weeks.

At 14 to 16 weeks, women have the option of screening through amniocentesis, in which a doctor uses a needle to withdraw amniotic fluid that contains fetal cells and can indicate the presence of Down syndrome or neural tube defects such as spina bifida.

Also, at about 18 to 20 weeks, a woman can have an ultrasound screening to scan for physical features of Down syndrome in her baby. The test is not 100 percent accurate, but can be very reassuring to the woman who doesn't want to undergo amniocentesis, which carries about a 1 in 350 risk for miscarriage, Young says.

For sure, screenings can help older pregnant women prepare for what is likely to come, but a woman's best bet for experiencing a healthy pregnancy and delivering a healthy baby is to make smart choices in the years leading up to pregnancy, and to continue good habits during pregnancy.

"If you're going to be 40 years old when you have your first child, make sure you take good care of yourself up to that point," Young says. "Start pregnancy at a healthy weight, start having not smoked, having not [abused alcohol] and having exercised regularly. Start a prenatal vitamin before you get pregnant … and get regular prenatal care."