Long before "Octomom" Nadya Suleman gave birth to octuplets, and "John and Kate" decided to have eight, devout Christian Michelle Duggar was quietly having babies the old-fashioned way.

The star of the TLC reality TV series "19 Kids and Counting," and her husband have long rejected birth control, allowing God to decide how many children they should have.

This week, they announced that God has decided they should have one more. At 45, Michelle Duggar, a grandmother of two, is pregnant again with her 20th child, who's due, she says, in April.

"We are so excited. I was not thinking that God would give us another one, and we are just so grateful," she told NBC's The Today Show this week.

While many are questioning why anyone would want to be having children into their mid-40s, others still are asking if it's even safe.

During her last pregnancy two years ago, Duggar developed a life-threatening condition called preeclampsia, in which her blood pressure rose to dangerous levels. The condition became severe enough that she had to be rushed in for an emergency caesarean section at just 26 weeks along.

Duggar's baby, named Josie, weighed only 1 pound, 6 ounces at birth, and spent six months in hospital for a series of health emergencies, including a perforated bowel. Duggar herself was also forced to stay in hospital for weeks.

Josie is now two years old and about 15 pounds -- a little underweight but otherwise healthy, her family says.

Whether Duggar will develop pre-eclampsia again remains to be seen. The condition can affect pregnancies randomly. In fact, Duggar developed it with her second pregnancy more than 20 years ago, but went on to have 15 more healthy pregnancies.

But the risk of the condition rises with age, notes Dr. John Kingdom, a staff obstetrician in the high-risk pregnancy unit at Mount Sinai Hospital in Toronto and a professr of obstetrics at the University of Toronto.

"The real problem if she does develop pre-eclampsia again is that aging, aging of her vascular system, will make her less able to tolerate it," he tells CTVNews.ca.

Worry of placenta problems

In Kingdom's mind, though, the greater worry for a mother who has had multiple pregnancies is the number of caesarean sections she's undergone,.

In Michelle Duggar's case she's had four C-sections. Kingdom says after two or three c-sections, there is the risk the placenta could grow through the wall of the uterus.

"Previous surgeries will scar the uterus. If the inside is scarred low down, it will attract the pregnancy low down, causing low-lying placenta or placenta previa," he explains.

"If the placenta then breaks through the first layer of the uterus, called the decidua, it can embed into the wall of the muscle, which is what we call placenta increta."

When a woman with this condition goes into labour, there is a high chance the uterus will rupture, causing severe hemorraging, which can threaten the life of the mother and baby.

Kingdom says that's why he insists that all mothers over 40 undergo a placental scan, to decide whether to schedule a c-section before labour begins.

Duggar says she's feeling well and is under the care of a high-risk pregnancy doctor, exercising regularly and doing her best to stay healthy.

In interviews with network TLC, Duggar quotes the Bible passage that says there is no greater love than to lay down your life for another. She says she would be willing to do that, "even for a child who is not here yet."

Beyond Duggar's own risks there are also the risks of birth defects, which rise dramatically after a woman reaches 40. At 45, Duggar had a 50/50 chance of a first-trimester miscarriage, because of chromosomal defects in the embryo.

Duggar is already more than three months along but her baby still has a 1 in 20 chance of having birth defects. The risk of such problems in all women is much lower, at 1 in 600.

Natural conception rare at 45

Fertility specialist Dr. Thomas Hannam, of the Hannam Fertility Centre in Toronto, says a woman of 45 who becomes pregnant naturally has already defied the odds.

"To conceive naturally at 45, it's a special event when it happens, because it just doesn't happen very often."

Hannam says the oldest person he's ever seen achieve a natural conception in his practice is 51.

But he points out that half of women who conceive naturally after age 40 lose that pregnancy in the first trimester. That's because the quality of a woman's eggs drops off in her late 30s and early 40s and the resulting embryos can have chromosomal problems that cause the pregnancies to fail.

But he points out that every woman is different, so some women will continue producing good eggs into their mid-40s. While Hannam doesn't know Duggar's case, he says any woman still giving birth into her 40s probably has high egg quality.

"A woman who has had 20 pregnancies has clearly been blessed with an absolute ton of eggs. There's no way around it," Hannam says. "If whenever she tries to get pregnant, she succeeds, that speaks to spectacular fertility."

The Duggars say they welcome this latest pregnancy and are not dwelling on the risks. They say that even the frightening circumstances of Josie's birth were not enough to convince them to fear becoming pregnant again.

"If we felt that way, we would have stopped back with our second birth," Michelle Duggar told People magazine.

"That whole mindset that you stop after a problem pregnancy isn't realistic... You may encounter struggles along the way. You may not have a perfect pregnancy, but each child is a precious gift."