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Existing  health conditions, such as high blood pressure, diabetes, or being  HIV-positive.
											 
											
											  
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Overweight  and obesity - According to the American Congress of Obstetricians and  Gynecologists, more than half of all pregnant women in the United States are  overweight or obese. Obesity increases the risk for high blood pressure,  preeclampsia, gestational diabetes, stillbirth, neural tube defects, and  cesarean delivery. NICHD researchers have found that obesity can raise infants'  risk of heart problems at birth by 15%.
											 
											
											  
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Multiple  births - The risk of complications is higher in women carrying more than one  fetus (twins and higher-order multiples). Common complications include  preeclampsia, premature labor, and preterm birth. More than half of all twins  and as many as 93% of triplets are born at less than 37 weeks’ gestation.
											 
											
											  
											- Young  or old maternal age - Pregnancy in teens and women aged 35 or over increases the  risk for preeclampsia and gestational high blood pressure.