Did Motherhood Kill Anna Nicole Smith?

The death of Anna Nicole Smith Thursday has fueled wild speculation, with theories on what killed the 39-year old tabloid celebrity ranging from drug overdose, to her remarkable weight loss, to homicide.

But with Smith dying roughly five months after giving birth to her daughter, Danielynn Hope Marshall Stern, the tragic news also serves of a sad reminder of just how vulnerable to maternal death women in the United States still are.

What is maternal death? As defined by the World Health Organization, it is "the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes."

Even such conditions as post-partum depression can factor into a woman's physical health following a pregnancy.

In some states, a woman's death can be ruled as a maternal death if she dies within 12 months of the end of her pregnancy. Anna Nicole Smith collapsed and died after being rushed to the hospital just 154 days after giving birth to her Dannielynn.

According to the Association of Maternal and Child Health Programs, despite the fact that the U.S. is one of the most medically and economically advanced countries in the world, American women experience unexpectedly high death rates during pregnancy and after childbirth. The agency says that two to three women in this country die each day from complications related to pregnancy, and 30 percent of all pregnant women experience some type of illness or injury beyond what is expected during a normal childbirth.

There are two types of maternal death: direct maternal death resulting from complications associated with the pregnancy, delivery, or their management; and indirect maternal death, in which the cause of death is pregnancy-related in a patient with a preexisting or newly developed health problem.

According to the WHO, the causes of maternal mortality are well established. Three quarters of maternal deaths result from the direct obstetric complications of hemorrhage, infection, obstructed labor, hypertensive disorders of pregnancy and septic abortion. The rest are the result of other obstetric causes such as pulmonary embolism or ectopic pregnancy, or indirect causes that are aggravated by pregnancy, such as diabetes, mellitus and heart disease.

A recent report published by the Royal College of Obstetricians and Gynecologists says that depression and obesity are now the major causes of deaths related to pregnancy in women in the United Kingdom. The report went on to note that indirect psychological and lifestyle factors posed a significant risk.

Did motherhood kill Anna Nicole Smith? Is it possible that her death was due to mental or physical complications related to giving birth to her daughter? Those are just some of the many medical questions that still need to be answered in this very sad case.

While the cause of Anna's death is still unknown, her lifestyle was not. On Sept. 10, just days after Smith delivered her daughter, Smith's 20-year-old son Daniel died in his mother's hospital room in the Bahamas from apparently drug-related causes. At the very least, in the case of Anna Nicole Smith, the possibility that her death was also influenced by drugs cannot be excluded.

The actual cause of death is under investigation and an autopsy will take place on Friday, the Broward County Medical Examiner's Office has stated.

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Dr. Manny Alvarez is the managing editor of health news at FOXNews.com, and is a regular medical contributor on the FOX News Channel. He is chairman of the Department of Obstetrics and Gynecology and Reproductive Science at Hackensack University Medical Center in New Jersey. Additionally, Alvarez is Adjunct Professor of Obstetrics and Gynecology at New York University School of Medicine in New York City.