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Children who were born to mothers who smoked and drank beyond the first trimester of pregnancy have an increased risk for SIDS or Sudden Infant Death Syndrome compared to children who were not exposed or those who were only exposed during the first trimester of pregnancy. This is according to a study that was supported by the National Institutes of Health. 

What is SIDS?

SIDS or Sudden Infant Death Syndrome is the unexplained, sudden death of a baby that is under one year of age. A lot of studies have shown that the risk of SIDS is increased by maternal smoking during pregnancy. Some studies have also found out that prenatal alcohol exposure, usually from heavy drinking during pregnancy, can increase the risk of SIDS. Now, the NIH-funded Safe Passage Study gives a look at how SIDS risk is influenced by the timing and the amount of prenatal exposure to alcohol and tobacco. A report of the study appears in an online journal that is published by The Lancet. 

The author of the study, Amy J. Elliott, Ph.D., of the Avera Health Center for Pediatric and Community Research in Sioux Falls, said that theirs is the first massive-scale prospective study to closely investigate the association between prenatal tobacco and alcohol exposure and the risk of SIDS. Findings suggest that combined exposures to alcohol and tobacco have an effect on SIDS risk, given that the dual exposure was linked with a substantially higher risk than either exposure alone. 

Effects of alcohol and tobacco on infants

In order to conduct the research, numerous teams of scientists from all across America and South Africa formed the Prenatal Alcohol in SIDS and Stillbirth Network, also known as PASS. Between 2007 to 2015, PASS Network researchers followed and recorded the outcomes of almost 12,000 pregnancies among women from two areas in Cape Town, South Africa and five sites in America. The states included two American Indian Reservations in North Dakota and South Dakota. The sites of the study were selected for their high rates of prenatal alcohol use and SIDS, and to include populations where the socioeconomic and ethnic disparities in SIDS remains understudied. 

The researchers noted one-year outcomes for 94% of the pregnancies. They found that 66 infants died during that time, including 28 SIDS deaths and 38 deaths from other causes. Additionally, the 12-fold increased SIDS risk from combined drinking and smoking beyond the first trimester of pregnancy, the researchers also noted that the risk of SIDS was increased five times in babies whose mothers reported that they continued smoking beyond the first trimester, and four times in babies whose mothers reported they continued drinking beyond the first trimester. These risks were in comparison to babies who were either not exposed to tobacco or alcohol during gestation or whose mothers quit tobacco or alcohol use by the end of the first trimester. 

Co-author of the study, Hannah C. Kinney, M.D., of the Department of Pathology at Boston Children's Hospital and Harvard School of Medicine said that the safe passage study gives important new information about the role of dual exposures to prenatal drinking and smoking as risk factors for SIDS. Their findings support the current recommendation of the U.S. Centers for Disease Control and Prevention, the U.S Surgeon General and the WHO that women do not smoke or drink during pregnancy, and emphasizes the risk of dual exposure, which provides as the greatest threat for infant mortality. 

The leaders of the NIH Institutes that gave funding for the Safe Passage Study said that these findings give more evidence of the importance of the early prenatal environment to healthy postnatal outcomes. Insofar, as a lot of women quit smoking and drinking only after they learn that they are pregnant, this study argues for screening for substance use early in pregnancy and intervening as soon as possible. It also calls for stronger public health messaging regarding the dangers of smoking and drinking during pregnancy, and among women who plan to become pregnant. 

ALSO READ: Sudden Infant Death Syndrome (SIDS): Cause & Safety Guidelines