Research Article: Maternal age and severe maternal morbidity: A population-based retrospective cohort study

Date Published: May 30, 2017

Publisher: Public Library of Science

Author(s): Sarka Lisonkova, Jayson Potts, Giulia M. Muraca, Neda Razaz, Yasser Sabr, Wee-Shian Chan, Michael S. Kramer, Jenny E Myers

Abstract: BackgroundOne of the United Nations’ Millennium Development Goals of 2000 was to reduce maternal mortality by 75% in 15 y; however, this challenge was not met by many industrialized countries. As average maternal age continues to rise in these countries, associated potentially life-threatening severe maternal morbidity has been understudied. Our primary objective was to examine the associations between maternal age and severe maternal morbidities. The secondary objective was to compare these associations with those for adverse fetal/infant outcomes.Methods and findingsThis was a population-based retrospective cohort study, including all singleton births to women residing in Washington State, US, 1 January 2003–31 December 2013 (n = 828,269).We compared age-specific rates of maternal mortality/severe morbidity (e.g., obstetric shock) and adverse fetal/infant outcomes (e.g., perinatal death). Logistic regression was used to adjust for parity, body mass index, assisted conception, and other potential confounders. We compared crude odds ratios (ORs) and adjusted ORs (AORs) and risk differences and their 95% CIs.Severe maternal morbidity was significantly higher among teenage mothers than among those 25–29 y (crude OR = 1.5, 95% CI 1.5–1.6) and increased exponentially with maternal age over 39 y, from OR = 1.2 (95% CI 1.2–1.3) among women aged 35–39 y to OR = 5.4 (95% CI 2.4–12.5) among women aged ≥50 y. The elevated risk of severe morbidity among teen mothers disappeared after adjustment for confounders, except for maternal sepsis (AOR = 1.2, 95% CI 1.1–1.4). Adjusted rates of severe morbidity remained increased among mothers ≥35 y, namely, the rates of amniotic fluid embolism (AOR = 8.0, 95% CI 2.7–23.7) and obstetric shock (AOR = 2.9, 95% CI 1.3–6.6) among mothers ≥40 y, and renal failure (AOR = 15.9, 95% CI 4.8–52.0), complications of obstetric interventions (AOR = 4.7, 95% CI 2.3–9.5), and intensive care unit (ICU) admission (AOR = 4.8, 95% CI 2.0–11.9) among those 45–49 y. The adjusted risk difference in severe maternal morbidity compared to mothers 25–29 y was 0.9% (95% CI 0.7%–1.2%) for mothers 40–44 y, 1.6% (95% CI 0.7%–2.8%) for mothers 45–49 y, and 6.4% for mothers ≥50 y (95% CI 1.7%–18.2%). Similar associations were observed for fetal and infant outcomes; neonatal mortality was elevated in teen mothers (AOR = 1.5, 95% CI 1.2–1.7), while mothers over 29 y had higher risk of stillbirth. The rate of severe maternal morbidity among women over 49 y was higher than the rate of mortality/serious morbidity of their offspring. Despite the large sample size, statistical power was insufficient to examine the association between maternal age and maternal death or very rare severe morbidities.ConclusionsMaternal age-specific incidence of severe morbidity varied by outcome. Older women (≥40 y) had significantly elevated rates of some of the most severe, potentially life-threatening morbidities, including renal failure, shock, acute cardiac morbidity, serious complications of obstetric interventions, and ICU admission. These results should improve counselling to women who contemplate delaying childbirth until their forties and provide useful information to their health care providers. This information is also useful for preventive strategies to lower maternal mortality and severe maternal morbidity in developed countries.

Partial Text: One of the United Nations’ Millennium Development Goals of 2000 was to reduce maternal mortality by 75% in 15 y [1], a challenge that spurred an interest in maternal mortality and morbidity [2,3]. This challenge was not met by many industrialized countries [4–6]. Moreover, recent reports suggest an increase in maternal deaths in the United States, with the maternal mortality ratio rising from 12 per 100,000 live births in 1990 to 14 per 100,000 live births in 2015 [6–9]. Several explanations have been offered for the increase, including improved ascertainment of maternal deaths, especially those resulting from indirect obstetric causes and late deaths occurring after 42 d postpartum [10], and a temporal increase in chronic health conditions in the child-bearing population. Past decades have seen a rise in the number of parturient women with hypertension, diabetes, chronic heart disease, obesity [11–15], and advanced maternal age [16–21], reflecting an increased complexity of obstetric care, requiring careful prenatal monitoring and timely obstetric interventions.

All analyses were performed on publicly accessible de-identified data. An exemption from ethics approval was granted by the Department of Social and Health Services of Washington State. This study is reported as per the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines (S1 Checklist).

Overall, 952,212 mothers gave birth (live or stillbirth) in Washington State between 1 January 2003 and 31 December 2013. We excluded births that occurred out of state, multiple births, births before 20 wk gestation, births to females aged <15 or >60 y (35,598 mothers, 3.7%), births that occurred out of hospital (24,716 mothers, 2.6%), and births that could not be matched with hospital records (64,609 mothers, 6.8%). The remaining 828,269 births were included in the study. Women who delivered out of hospital or whose birth could not be matched with hospital records were not substantially different from those included in the study, except for type of health insurance (they were more likely to have “other” insurance—other government insurance, student insurance, Indian Health Care, other health insurance programs, or no insurance; S2 Table).

Our results show elevated rates of severe maternal morbidity at the extremes of maternal age. While the elevated risk among teenage mothers was mostly due to an increased rate of sepsis, rates of all other causes of severe maternal morbidity were elevated among older mothers (≥40 y). The absolute rates and ORs were lower after adjustment for demographic and pre-pregnancy factors but remained elevated for sepsis among teenage mothers and for all other morbidities among older women. Our results confirm that perinatal mortality and neonatal morbidity are elevated among teenage mothers and older mothers, as compared with mothers aged 25–29 y [22–25]. The association between teenage motherhood and most adverse perinatal outcomes disappeared after adjustment for maternal demographic factors, with the exception of the neonatal death rate, which remained 50% higher.



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