Delaying parenthood has become common, shifting the average age of first-time mothers upward. This trend raises a key question: is it harder to get pregnant after age 40? Reproductive science confirms that while conception is possible, biological and medical factors introduce significant challenges. This article explores the biological constraints, health considerations, and medical guidance for individuals pursuing pregnancy after 40.
The Biological Reality of Age and Ovarian Reserve
The primary challenge to conception after age 40 is the natural decline in the quality and quantity of a woman’s eggs, known as ovarian reserve. A woman is born with a finite supply of eggs, which diminishes over time. By age 40, the chance of conceiving naturally in any given menstrual cycle drops significantly, estimated to be around 5% to 10%.
The sharp decline in egg quality, which accelerates after age 35, is the more impactful factor. Egg quality relates to the genetic state of the egg, specifically whether it contains the correct number of chromosomes (euploidy). Older eggs are more likely to accumulate errors during cell division, leading to an incorrect number of chromosomes, or aneuploidy. This is the main biological hurdle for women over 40.
At age 40, the majority of eggs are chromosomally abnormal; up to 60% of embryos may be aneuploid. This high rate of genetic abnormality makes successful implantation and live birth less likely. Consequently, the risk of miscarriage rises sharply, reaching about 40% for women in their 40s, compared to 15% for women in their 20s.
Increased Maternal and Fetal Health Risks
Pregnancy after age 40 is associated with increased health risks for both the mother and the fetus. Advanced maternal age is an independent risk factor for several complications, necessitating more vigilant prenatal monitoring.
Maternal complications are more frequent, including an increased risk of developing gestational hypertension and preeclampsia. Women over 40 are also more likely to experience gestational diabetes. Additionally, the likelihood of needing a Cesarean section is nearly double that of younger women.
The fetus faces elevated risks, including preterm birth, low birth weight, and stillbirth. The risk of a baby having a chromosomal abnormality, such as Down Syndrome (Trisomy 21), also increases significantly. This is a direct consequence of the higher rate of aneuploidy in older eggs.
Navigating Conception: Timelines and Medical Evaluation
Due to the time-sensitive nature of age-related fertility decline, the timeline for seeking medical evaluation is shorter for women over 40. While younger women are advised to try conceiving for 12 months, a woman aged 40 or older should consult a reproductive specialist after six months of unsuccessful attempts. Some experts recommend seeking an evaluation immediately upon deciding to try.
The initial medical evaluation assesses ovarian reserve and reproductive health. Diagnostic steps begin with blood tests to measure hormone levels. The Anti-Müllerian Hormone (AMH) provides an estimate of the remaining egg supply. Follicle-Stimulating Hormone (FSH) levels, measured early in the menstrual cycle, offer insight into ovarian function.
A transvaginal ultrasound is also used to count the number of small resting follicles, known as the antral follicle count (AFC). The results from the AMH, FSH, and AFC help the specialist determine the individual’s biological fertility profile and guide the discussion toward appropriate next steps.
Assisted Reproductive Options for Advanced Maternal Age
When natural conception is challenging, assisted reproductive technologies (ART) can be utilized. In Vitro Fertilization (IVF) is the most effective option for advanced maternal age. However, IVF cycles using a woman’s own eggs over age 40 have a significantly lower live birth rate compared to younger women, averaging around 11.6% for women over 40 and dropping to about 3% for those over 42.
Preimplantation Genetic Testing (PGT) is often recommended during IVF to screen embryos for aneuploidy before transfer. PGT identifies chromosomally normal, or euploid, embryos. Transferring a euploid embryo has a much higher chance of successful implantation and live birth, potentially increasing the success rate to a level similar to that of younger women.
If the quantity or quality of a woman’s own eggs is diminished, using donor eggs offers the highest chance of success. Using eggs from a young donor bypasses the issue of age-related aneuploidy. This can result in a live birth rate of over 70% per cycle in some studies. Egg freezing is also an option women may have pursued proactively at a younger age to preserve egg quality.