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Stillbirth risk factors every woman should know

Robin Wulffson MD's picture
stillbirth, risk factors, preterm birth small for gestational age, smoking

NEW SOUTH WALES AUSTRALIA – A stillbirth is a devastating experience for any woman who has suffered one. A new study was published in the March 2012 edition of the journal Obstetrics & Gynecology, which had the goal of estimating the risk of stillbirth in a second pregnancy when a previous stillbirth, preterm, or small-for-gestational age (SGA) birth occurred in the previous pregnancy.

Researchers affiliated with Sydney University, Royal North Shore Hospital noted that stillbirth is estimated to occur in 2.65 million births globally each year. They added that reported recurrence risks vary widely with estimates ranging from a two to a 10-fold increase. To further delineate which women would be at increased risk for a stillbirth, they conducted a population-based study in New South Wales, Australia from 2002 to 2006. New South Wales is the most populous state in Australia and its 90,000 births per annum account for approximately 30% of the nation's births.

Singleton births (one infant) in a first pregnancy were linked to a second pregnancy using data from the New South Wales Midwives Data Collection and the New South Wales Perinatal Death Database. The researchers found that delivery of an SGA newborn in the first pregnancy was associated with increased risks of stillbirth in a second pregnancy and risk was further increased with prematurity. Stillbirth in a first pregnancy was found to have a non-significant association with stillbirth in the second pregnancy. For women aged 30–34 years, the absolute risk of stillbirth up to 40 completed weeks of gestation was 4.84 per 1,000 among women whose first pregnancy was a stillbirth and 7.19 per 1,000 among women whose first pregnancy was preterm and SGA.

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The authors concluded that delivering an SGA and preterm infant in a first pregnancy is associated with greater risks for stillbirth in a second pregnancy than delivering a previous stillbirth. The authors noted that all factors merit improved surveillance in a subsequent pregnancy, and research should address underlying factors common to all three outcomes.

Take Home Message: To some extent, the unfortunate pregnancy outcomes cited in the study, stillbirth, premature birth, or a small-for-gestational-age birth, are beyond a woman’s control; they are a result of environmental factors, genetics, or just bad luck. However, lifestyle choices can greatly increase the risk of a bad pregnancy outcome. Among them are an unhealthy diet, substance abuse, alcohol abuse, or smoking. Many women who lead an otherwise healthy lifestyle smoke cigarettes. Smoking during pregnancy is a form of child abuse; it increases the risk of miscarriage, preterm birth, low for gestational age infants, and stillbirths. When a woman smokes, the oxygen supply to the placenta is decreased. In addition, harmful substances in tobacco, including carcinogens, pass through the placenta to the fetus. Nicotine replacement is less harmful than cigarette smoking; however, the drug causes constriction of arteries; thus reducing fetal blood supply.

Many smokers who become pregnant make a concerted effort to quit; however, smoking is a very difficult habit to kick. A number of studies have noted that it is easier to kick a heroin habit than smoking. A study published March 1, 2012 in The New England Journal of Medicine reported that nicotine patches, which have been proven effective in the general population, do not increase the rate of smoking cessation between women who receive anti-smoking support plus nicotine passages and women who only receive anti-smoking counseling. The best option for a pregnant smoker is to quit cold turkey. In fact, some studies have reported that this approach is as equally effective as nicotine patches.


Obstetrics & Gynecology
The New England Journal of Medicine