Rising preterm birth rates: Time to double down on our efforts
Dr Lockwood, editor in chief, is Senior Vice President, USF Health, and Dean, Morsani College of Medicine, University of South Florida, Tampa. He can be reached at [email protected].
The Centers for Disease Control and Prevention (CDC) preliminary report of 2015 birth outcomes contains some heartening news.1 The birth rate for teenagers aged 15 to 19 years continues to fall, dropping 8% in just 1 year, 46% since 2007 and 64% since its peak rate in 1991. And while the decrease wasn’t of the same magnitude, cesarean delivery rates also fell for the third year in a row to 32% from 32.2%. Moreover, the cesarean rate for low-risk women (ie, nulliparas with singleton fetuses in vertex presentations at term) dropped to 25.7% from 26.0%.
Unfortunately, after nearly a decade of declines, the US preterm birth (PTB) rate rose from 9.57% in 2014 to 9.62% in 2015. Interestingly, this increase was largely confined to late (34 to 36 weeks) PTBs, which increased from 6.82% to 6.87%. The increase was also fueled by a widening of the already serious racial disparity in PTBs. Rates increased among non-Hispanic black women from 13.23% to 13.39% while declining among non-Hispanic whites from 8.91% to 8.88%. While all these changes are small, they should be a wake-up call to reinvigorate our efforts to fully implement proven strategies to reduce PTBs.
Do what works to prevent excess preterm births
The March of Dimes has been strongly advocating 7 strategies to reduce PTBs; my version of these interventions include:
Reducing non-medically indicated deliveries prior to 39 weeks. It is unclear whether the current modest increase in late PTBs, especially among African-American women, reflects a loosening of our collective resolve to vanquish truly elective preterm deliveries or an increase in bona fide medically indicated PTBs. Given changing maternal demographics, I suspect the latter. Birth rates are declining not just among teenagers but also among women aged 20 to 24 years, who experienced a 3% decline from 2014 and a 27% drop since 2007. Conversely, birth rates are up among women aged 35 to 39 years, rising 1% since 2014 and 13% since 2013. There were also more births to women aged 40 to 49 years last year. In a large cohort study, Khalil and colleagues noted that, after adjusting for other confounders, maternal age ≥40 years increased the occurrence of preeclampsia (odds ratio [OR] of 1.49; 95% CI: 1.22–1.82), gestational diabetes (OR of 1.88; 95% CI: 1.55–2.29), and small-for-gestational-age infants (OR of 1.46; 95% CI: 1.27–1.69), all risk factors for indicated PTB.2 Interestingly, this “advanced” maternal age was not associated with increases in spontaneous PTB. Weight tends to increase with age, and obesity, especially when body mass indices (BMIs) reach or exceed 40, is a risk factor for both medically indicated and, to a lesser extent, spontaneous PTB.3
Thus, the aging of our maternity wards, combined with the ongoing obesity epidemic, could certainly help account for a rise in indicated PTBs. The observed increase in racial disparity may either parallel these secular trends or be an independent contributor. Clearly we should avoid performing truly elective PTBs but a reduction in indicated PTBs will take a concerted societal effort to encourage women to reduce preconception weight and excess gestational weight gain through diet and exercise. It will also necessitate more aggressive blood pressure and glucose control among hypertensive and diabetic patients, respectively, both prior to and during pregnancy. Finally, it may also be time to for an honest discussion with younger women about the benefits of planning pregnancies between the ages of 25 and 35 years.