Brian and Shelane Gaydos with daughters, Nadia, Olivia, and Sophia. Shelane Gaydos was a Fairfax County police officer and killed herself after a miscarriage in June 2015. Her family believes she suffered from postpartum psychosis. Picture: Sarah Bryant.

Washington - Shelane Gaydos always wanted a big family. The Herndon, Virginia, woman and her husband, both Fairfax County police officers, had three little girls and were expecting their fourth child when they learned during a routine 12-week ultrasound that the baby's heart had stopped beating.

Gaydos was devastated. In the days that followed, she blamed herself, worried aloud that she had let her husband down, and told her sister that she felt like a failure. She took time off work, stopped sleeping. Two weeks after the doctor's appointment, she ended her life.

Her family and friends have spent the past two years trying to understand what happened to the 35-year-old woman they knew to be ambitious, passionate and fiercely dedicated to her children.

"It was natural, of course, that she would be depressed," said her mother, Joanne Bryant of Fairfax Station, Virginia, who is now helping to raise her three grandchildren. "We did not know to what degree."

Gaydos's family believes her death was the result of postpartum psychosis, a rare illness that can cause delusions and paranoia. And they have become advocates for raising awareness about the range of mentalhealth issues - often referred to in somewhat misleading shorthand as postpartum depression - that can affect expectant or new mothers.

At least 1 in 7 women experience anxiety or depression during pregnancy or in the first year after birth, making mental-health disorders the most common complication of pregnancy. Despite this, maternal depression remains vastly underdiagnosed and undertreated, with just 15 percent of women affected seeking professional help.

About 80 percent of women experience "baby blues" within the first few weeks of child birth, often defined by mood swings and irritability or sadness. Maternal depression is longer lasting and has more-severe symptoms, which can include anxiety, sleeplessness, extreme worry about the baby, feelings of hopelessness, and recurrent "intrusive thoughts" about hurting themselves or the baby.

Women are more likely to attempt suicide during the first year after childbirth than during any other time in their lives, and they tend to choose more lethal means.

These mood disorders are triggered by fluctuating hormones, including estrogen and progesterone, that ramp up during pregnancy and then drop off sharply after birth. Another significant hormonal shift occurs when women stop breast-feeding.

Researchers are trying to understand what predisposes some women to be more sensitive to these hormonal fluctuations, while others are not.

It's clear that environmental stressors play a role. The prevalence of depression is far higher for women who are poor or in abusive relationships or for women whose babies are born premature or disabled.

The stress of having a child is also exacerbated by unrealistic societal expectations, advocates say, and a poor social safety net that offers no federal paid leave program for new mothers.

"Women are supposed to have a full-time job, breast-feed, fit into a Size 6, go back to work a week after their baby is born, and do it all themselves, not to mention without sleeping," said Jamie Zahlaway Belsito, advocacy chair of the National Coalition for Maternal Mental Health.

Studies have shown that untreated maternal depression can harm not just mothers but also their children, and can lead to delays in cognitive and emotional development. Severe depression during pregnancy is associated with health risks, including pre-eclampsia and preterm delivery.