Research shows caffeine leads to an increased risk of miscarriage and prompts more questions about coffee drinking for obstetricians like Dr. Susan Harvey.

“This week and forever,” said Harvey.

Harvey has been part of the Seattle Obstetrics & Gynecology Group for nearly 20 years. Her coffee advice to patients, who mostly deliver at Swedish Medical Center, hasn’t changed much during her tenure.

“There was a large study published about 20 years ago that showed caffeine in large amounts increased a woman’s risk of miscarriage,” says Harvey. “Of course, back then, a large amount equated to a pot of coffee. These days we drink lattes.”

Either drip or espresso, Harvey and her colleagues have long recommended that pregnant women “limit exposures” to avoid any increased possibility of miscarriage.

Recent studies, for the first time, have controlled for the morning sickness factor or the symptoms of vomiting and nausea that lead many women to avoid coffee altogether in early weeks of pregnancy.

“Lots of women don’t feel that well during the first two to three months, so they don’t feel like drinking coffee,” said Harvey. “They opt out by choice.

Findings arguably represent a stronger precaution against caffeine intake from all sources—including coffee, tea, sodas and chocolate—because th e pregnant participants kept their daily coffee habits as usual. Those habits ranged from none to moderate to heav

Dr. De-Kun Li, a caffeine and miscarriage researcher, has said the “main message” is pregnant women should consider stopping caffeine consumption during pregnancy and that sodas, tea and hot chocolate can have a similar negative effect as coffee. She said caffeine crosses from the placenta to the fetus, and that the fetus has a underdeveloped metabolic system that struggles to process the caffeine. There is also some scientific evidence to suggest caffeine disrupts healthy cell development and decrease placental blood flow to the baby.

Other risk factors such as smoking, certain infections and a mother’s advancing age (35 and older) are more strongly linked to potential miscarriage than caffeine intake.