Risks of Midlife Pregnancy

What is the problem and what is known about it so far?
Women are choosing to delay childbearing until later in life. While the increased rate of chromosomal abnormalities is well recognized, it is not known how other complications of pregnancy are affected by age. Early studies showed that pregnancy may be riskier in older women but the true impact of age on risk is unknown. For any woman considering pregnancy, it is important to understand the risk associated with childbearing.

Why did the researchers do this particular study?
The researchers performed this study to provide risk information to women as they plan their family and to provide potential preventative measures and treatment strategies.

Who was studied?
36,056 pregnant women throughout the United States were studied. All women were between 10 and 14 weeks pregnant.

How was the study done?
Information about pregnancy complications was collected as a part of another large study performed in the United States. The rate of specific pregnancy complications was described for 3 age groups: less than 35 years, 35 to 40 years and greater than 40 years old. The rate of complications in the two groups of women over the age of 35 were compared to women less than 35 years old.

What did the researchers find?
Older women frequently had a medical condition prior to pregnancy, with diabetes and hypertension the most common diseases (women <35 years: 36%; 35-40 years: 44%; over 40 years: 52%). The risk of miscarriage was approximately twice that in older women compared to younger women (<35: 0.8%; 35-40: 1.5%; over 40: 2.2%) The risk of chromosome abnormality was approximately 10 times higher in older women (<35: 0.2%; 35-40: 0.8%; over 40:1.9%). The risk of hypertension or diabetes during pregnancy was doubled with increased maternal age (hypertension: <35: 4.7%; 35-40: 4.1%; over 40:); (diabetes <35: 2.9%; 35-40: 5.3%; over 40: 7.3%). The risk of having a premature infant was increased by 40% for mothers over 40 (<35: 7.8%; 35-40: 8.6%; over 40:11.8%). The risk of requiring a cesarean delivery was doubled (<35: 22%; 35-40: 31%; over 40: 41%).

What were the limitations of the study?
This study relied on accurate history taking and entry into the computer. Most of the hospitals involved in the study were large hospitals and may have a different patient population than smaller hospitals. Nonetheless, the large number of women included in the study makes the information very reliable.

What are the implications of the study?
Older women usually deliver healthy babies, although the risk of specific complications is increased with maternal age. It is reasonable for all women to discuss pregnancy plans with a health care provider, as over one third of the younger women in this study had a medical condition prior to pregnancy. Optimal management of medical problems before pregnancy ensures the best possible pregnancy outcome.

Summarized by Anna Benvenuto, College of Medicine, University of Vermont.
Summarized from "Impact of Maternal Age on Obstetric Outcome". Cleary-Goldman J. et al. Obstetrics and Gynecology. May 2005, Volume 105, pages 983-990.