Advanced maternal age

In much of the industrialized world, social, educational, and demographic changes have led to an increasing number of women postponing their pregnancies until later in life. Later marriage, second marriage, and pursuit of education or careers are examples of this. This social trend, combined with the accessibility to birth control and infertility treatment, has increased the proportion of women experiencing their first pregnancy after 35 years of age.

Over the last 50 years, the average age for first pregnancy has been increasing. Advanced maternal age is defined as giving birth at age 35 or older. While many women over 35 will have easy, uncomplicated pregnancies, there are several risk factors to consider.

  • Conception
  • Fetal complications
  • Maternal complications
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Fertility will begin to decline for some women in their early 30s. A much sharper decline in fertility can be seen after age 37. For healthy couples in their 20s and 30s, approximately 1 in 4 will become pregnant in any given menstrual cycle. For couples in the 40s, the rate is 1 in 10 for any single menstrual cycle. Females are born with their lifetime supply of eggs or oocytes. Over time, the number of eggs will diminish, as will egg quality. At puberty, there are 300,000 oocytes, and by age 37-38, there are only 25,000 remaining. Age is the best predictor of fertility.

Fetal complications

As the ovaries and eggs age, the risk of chromosomal disorders will increase.

First-trimester miscarriage

The overall risk of fetal loss is approximately 15%. The risk of fetal loss rises steeply after age 35 to greater than 20%. By age 42, this risk is greater than 50%.

Chromosomal abnormalities

Most first trimester miscarriages result from a chromosomal abnormality, often an incorrect number of chromosomes.  Most of these are incompatible with life which is why the miscarriage occurs.  A few chromosomal abnormalities are compatible with in utero life, and these are the ones for which genetic screening tests are available.  Specifically, these are trisomy 21 (3 copies of chromosome 21, or Down syndrome), trisomy 18 (3 copies of chromosome 18), and trisomy 13 (3 copies of chromosome 13).  The chances of having a pregnancy affected by Down syndrome are

  • 1 in 1,480 at age 20
  • 1 in 940 at age 30
  • 1 in 353 at age 35
  • 1 in 85 at age 40
  • 1 in 35 at age 45

Maternal complications

Optimizing maternal health is an important goal before becoming pregnant, especially for those women who will be over 35.  Advanced maternal age carries an increased risk of 

  • Gestational diabetes, which is glucose intolerance that develops in pregnancy.  Women who develop diabetes in pregnancy have an increased lifetime risk of diabetes
  • Gestational hypertension, which is elevated blood pressure that develops in pregnancy
  • Preeclampsia, which is elevated blood pressure, swelling, and protein in the urine
  • Multiple births – the chance of twins is higher in women over 35

Advanced maternal age also carries an increased risk of Cesarean section.  A Danish study found that the Cesarean section rate doubled in women age 35-39 and tripled in women over 40.  

The providers at Northside Northpoint OB/GYN have the experience and expertise to provide comprehensive and compassionate care for your advanced maternal-age pregnancy.

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