Obesity can cause a lot of problems, from type 2 diabetes to an increased risk of heart attack. But obesity among women can also be harmful to the children to whom they give birth — from causing pregnancy complications, to a higher risk for the kids to develop childhood obesity.

Now, in a new study, researchers have found that pregnant women who are obese have a higher risk of causing kidney and urinary tract problems for their kids. The study will be presented at American Society of Nephrology (ASN) Kidney Week 2014 at the Pennsylvania Convention Center in Philadelphia.

Maternal obesity has been linked to other congenital defects in the past, such as missing limbs, not fully-formed hearts, and problematic spinal cords. Congenital abnormalities of the kidney and urinary tract, also known simply as CAKUT, occur in about one percent of all pregnancies. Since researchers began noticing a link between obesity and other forms of defects, they wanted to see if obesity was also a factor when it came to CAKUT.

The researchers examined birth-hospital discharge records from Washington State between 2003 and 2012, and found that mothers who gave birth to children with CAKUT were 1.3 times as likely to be obese than mothers whose children were born completely healthy. But overweight mothers did not appear to have the same effect on their children; it was only linked to obese women. “Our findings add to the public health importance of obesity, particularly as a modifiable risk factor,” Dr. Ian Macumber, lead author of the study, said in the press release. “The data supplement the literature regarding obesity’s association with congenital abnormalities and highlight the importance of future research needed to clarify the mechanisms of these associations.”

The U.S. has been home to an obesity epidemic for the past several years, and it seeps into future generations through these birth defects and increased likelihood for the kids of obese parents to become overweight themselves. “In the United States, more than one-third of women are obese, more than one-half of pregnant women are overweight or obese, and eight percent of reproductive-aged women are extremely obese, putting them at a greater risk of pregnancy complications,” the American College of Obstetricians and Gynecologists writes on its website. The babies of overweight and obese women have a higher risk of birth complications, such as prematurity, stillbirth, congenital anomalies, and of course, childhood obesity. In addition, obese women have a higher risk of complications for themselves, such as gestational diabetes mellitus, hypertension, preeclampsia, and postpartum weight retention.

Doctors advise women who want to have children to lose weight before getting pregnant, rather than attempt to get on a crash diet during the pregnancy. This is because it’s hugely important for a pregnant woman to consume the proper nutrients to feed her growing child. “You have to be of a healthy weight not only for yourself but also for a healthy pregnancy,” Dr. Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York City, told ABC News. “You want to try to get down to a healthy weight before you even get pregnant in the first place. Pregnancy is not the time to do a crash diet to try to lose weight.”