Pregnancy Complications at an Advanced Maternal Age

Posted On: December 30, 2015 By Nathan D. Fox, MD

older pregnant woman

Women of advanced maternal age (AMA, typically defined as 35 or more years old at deliver) have an increased risk of adverse pregnancy outcomes as compared to younger women. The following are several complications that have an increased risk in women of advanced maternal age.

Spontaneous abortion − Older women are more likely to experience early pregnancy loss, with both of aneuploidy (abnormal number of chromosomes) and euploid (normal number of chromosomes) fetuses. The risk of miscarriage steadily increases as women age. Women ages 35-39 are 25% more likely to have a miscarriage, and that chance increases to 51% for ages 40-44. Even after the fetal heart activity is detected, older women are still at a risk for later first trimester and early second trimester losses.

Ectopic pregnancy – A pregnancy that occurs outside of the uterus is known as an ectopic pregnancy. Studies have shown that older women have a four to eight-fold increased risk of ectopic pregnancy. However, this may be due to decreased tubal motility or increased use of infertility treatments.

Chromosomal abnormalities – There is a steady rise of an abnormal number of chromosomes in a cell, or aneuploidy, as women age. This risk can be modified significantly through blood testing and targeted ultrasound for assessment. All women have the ability to choose invasive testing (CVS or amniocentesis), to diagnose or rule-out aneuploidy. To review their options, women may go through genetic counseling to determine what course of action is right for her.

Congenital malformation – These complications, including cardiac malformations, diaphragmatic hernia, and clubfoot, can occur increasingly in offspring of older women. This is not related to aneuploidy, but the ability to diagnose the malformations with antenatal ultrasound is similar. It is recommended to have two ultrasound evaluations in the second trimester to assess the fetal anatomy..

Late pregnancy complications – Although some obstetrical problems are related to the mother’s age, these complications can also be related to multiple gestations, higher parity, and coexisting medical conditions that are more likely to be present in older women. The two most common medical problems that complicate pregnancy are hypertension and diabetes.

  • Hypertension – This is the most frequent medical complication associated with pregnancy in older women. Older women have a two to three-fold higher risk of being diagnosed with hypertension. Preeclampsia, or high blood pressure during pregnancy, can occur in 5-10% of women over the age of 40; and as high as 35% of women over the age of 50. We recommend women over the age of 35 take baby aspirin and calcium to reduce the risk of hypertensive disorders of pregnancy.
  • Diabetes – Compared to women in their 20s, rates of both preexisting diabetes mellitus and gestational diabetes increases three to six-fold in women over the age of 40. This affects the mother by increasing the blood sugar, which can cause further complications during pregnancy if not diagnosed and treated.

Placenta problems – Problems including placental abruption and placenta previa are more likely among older women. Women who have never had a child, and are 40 years or older, are shown to have a ten-fold increased risk of placenta previa compared to women aged 20-29. However, the overall risk is still relatively small.

Preterm birth – Preterm birth and infants with low birthweight are more common risks for women at an advanced maternal age. A large prospective study in Sweden determined the rates of preterm birth (before 32 weeks) are: 1.01% for women in their 20s, 1.80% for women 40-44, and 2.24% for women older than 45 years of age.  This increased risk is mostly due to complications of pregnancy requiring early delivery, as opposed to spontaneous premature labor.

Dysfunctional labor and cesarean delivery – There is a prominent relationship between maternal age and the risk of cesarean delivery (C-section). The overall C-section delivery rate in the U.S. is approximately 30%, whereas it isapproximately 50% in women ages 40-45 and almost 80% in women over 50. The causes of this are controversial, but include labor dysfunction, as well as an increased frequency of medical complications, induction of labor, and fetal malposition (breech position, for example).

Perinatal mortality – It has been consistently reported that there is an increased risk of stillbirth in older women compared to younger women. Large studies also show an increased risk of unexplained fetal death, even after controlling medical conditions. Due to this increased risk of stillbirth unrelated to other pregnancy complications, we recommend for women 35 years or older to have weekly antenatal testing (Biophysical Profile, or BPP) starting at 36 weeks.   We have published data showing that using this protocol, the stillbirth rate in AMA women can be reduced to that of younger women.

Despite these increased risks, with good prenatal care and focused testing and treatments, most women with advanced maternal age can have successful and safe pregnancies resulting in the birth of a healthy child to a healthy mother.

Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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