Should 'Advanced Maternal Age' Be Redefined?

Pregnant women who were at or above the advanced maternal age (AMA) cutoff of 35 years on their due date received significantly more prenatal care, resulting in a slight decline in perinatal mortality, compared with women who were just a few months younger, according to a new study published in JAMA Health Forum. The findings "suggest that clinicians use the cutoff as a heuristic in their clinical recommendations and service provision," noted lead author Caroline K. Geiger, PhD, who was a PhD student at Harvard University in Cambridge, Mass., during the course of the study, and now works as an associate health economist at Genentech in San Francisco. She and her coauthors suggest a slightly younger AMA cutoff might be beneficial. "Our results suggest that 3.9 perinatal deaths per 1,000 deliveries in this age range could be averted if patients just a few months younger than the AMA cutoff received similar care to those older than the cutoff," they wrote. "Although the risk of adverse outcomes increases with maternal age, individuals 4 months older or younger than 35 years should not have different underlying risks."

The cross-sectional study used a national sample of 51,290 commercially insured individuals who were pregnant between 2008 and 2019 and had delivery dates within 120 days of their 35th birthday. Just over half (50.9%) of the individuals were aged 34.7-34.9 years on their expected delivery date – just below the AMA cutoff – while 49.1% were just over the cutoff at age 35.0-35.3 years. A total of 4.7% had multiple gestation, 4.8% had pregestational diabetes, 4.4% had chronic hypertension, and 9.7% had obesity. There was also a subgroup analysis among individuals with low-risk pregnancy (defined as singleton, with no pregestational diabetes, chronic hypertension, or obesity) because they were less likely to have indications for additional prenatal care.

Although there was a slight, nonstatistically significant increase in the overall number of ob.gyn. visits at the AMA cutoff, compared with below it, the percentage of individuals with any maternal-fetal medicine visit increased by 4.27 percentage points (P < .001) at the cutoff. Additionally, while there was a "modest" increase in total ultrasounds (P = .006), there was a significant increase in detailed ultrasounds (P < .001) at the cutoff, and a "substantial" increase in antepartum surveillance (P < .001), the authors reported.

The AMA designation was associated with a 0.39 percentage-point decline in perinatal mortality (P = .04), "however, there were no significant changes in the proportion of individuals with severe maternal morbidity or with preterm birth or low birth weight at age 35 years," they wrote.

In the subgroup analysis of low-risk pregnancies, "prenatal care services increased substantially at the 35-year cutoff, and in all cases, the increases at age 35 years for this group were larger than for the full sample," they noted, adding that there was also a "substantially larger" decline in perinatal mortality at the AMA cutoff (P = .002), compared with the full sample.

The authors noted the need for more rigorous evidence on the value and effect of prenatal care guidelines on pregnancy outcomes. "Although pregnancy-related risks increase with maternal age, there is no known abrupt biological increase in underlying risk precisely at age 35 years," they wrote, adding that "much of the content of prenatal care guidelines has persisted for decades without strong causal evidence to demonstrate its value."

Their words echo those of Alex F. Peahl, MD, an ob.gyn. and assistant professor at the Institute for Healthcare Policy and Innovation, at the University of Michigan, in Ann Arbor, MI. In a recent review, Peahl and her colleague Joel D. Howell, MD, PhD, from the same university (Am J Obstet Gynecol. 2021 Apr;224[4]:339-47), note that the COVID-19 pandemic forced a much-needed rethink of prenatal care and its delivery. A look through the history of prenatal care shows "we have treated visit frequency and modality as fixed boxes, into which we must fit an ever-changing set of care recommendations," they wrote. "We do not have data to support a specific prenatal visit schedule, recommended number of telemedicine visits, or specifications of additional services, and we never have. However, one thing is clear: we are long overdue for new prenatal care delivery guidelines in the United States."

But when reached for comment on the new study Peahl cautioned that its conclusions are "limited and warrant future investigation. … While increased prenatal services may explain the improvement in outcomes, several other explanations should be considered," she told this publication. "Perhaps, maternity care professional behavior differs for patients who are over the age of 35, resulting in increased caution in interpreting test results and symptoms; perhaps patients are more routinely induced at 39 weeks, limiting stillbirth rate; or perhaps patients are more hypervigilant when given the diagnosis of AMA."

Priya Rajan, MD, agreed that while the paper showed an association between intensified antenatal interventions and decreased perinatal mortality, it did not show a causal relationship. "The study did not include information on other important factors that are also associated with perinatal risk," noted Rajan, who is an associate professor in the department of ob.gyn. at Northwestern University in Chicago. Yet, she acknowledged that the findings "support what many clinicians know, which is that age 35 isn't some tipping point; rather, obstetric risk is influenced by a range of factors, of which age may be one. This study, particularly when considered in the context of other studies and articles we have seen recently, confirms the need for us to rethink how we care for people during pregnancy and post partum. This includes delving further into understanding what aspects of the prenatal care that we provide have the biggest impact for both maternal and perinatal adverse outcomes."

The study was supported by grant DGE1745303 from the National Science Foundation Graduate Research Fellowship Program. Geiger reported being a PhD student during the conduction of the study, but had no other disclosures. Peahl will soon be a consultant for Maven Clinic. Rajan had no relevant disclosures.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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