"Embryo splitting occurs approximately in one out of 100 embryo transfers," Grifo said. "The chance of this outcome is approximately one in 10,000. This could also occur in a natural conception, but the chance of that is much [rarer].
"We have done around 20,000 IVF cycles and have fortunately not seen this outcome," he said. "It represents a very risky obstetrical situation, but it sounds like they were fortunate and had a good outcome."
"This is so rare, it is almost a record," said Dr. Michelle Warren, medical director for the Center for Menopause, Hormonal Disorders and Women's Health in New York. "However there is a view that only one embryo should be implanted at a time, particularly in patients with proven success. The issue is cost and if IVF wasn't so expensive, this would undoubtedly be standard of care."
Warren said many European countries do not allow more than one embryo at a time because of the high risk and cost of multiple pregnancies, along with health problems with the babies.
Identical twins following IVF tend to share a placenta and one of the pregnancy membranes, which makes the twin pregnancy riskier in terms of harsh growth conditions and death in the womb for one of the twins.
The risk of preterm labor and delivery is very high with any sort of multiple births. Babies born premature are at an increased risk for many health complications, including learning disabilities, lung problems, cerebral palsy, blindness and deafness.
Because the pregnancy was so high-risk, doctors gave the Crawfords several options, including reduction, where one or some of the fetuses are aborted for the safety of the mother and the other growing babies.
The Crawfords said they never considered reduction.
Overall Healthy Pregnancy
Miranda developed gestational diabetes during the pregnancy, which she managed by controlling and restricting her diet.
"My sugars were very low, but it only lasted a little while," she said. "It worked itself out before the babies came."
She was also hospitalized twice in December when doctors feared she might go into preterm labor.
But for the circumstance, the couple said the pregnancy went very well, considering the risk.
Doctors put Miranda on strict bed rest in December. By the time she was ready to give birth, she had gained 60 pounds and her midsection measured in at five feet around.
"Even at 20 weeks, I looked like I was nine months pregnant," said Miranda. "I was huge."
Babies, Babies, Babies
Mia, Madison, Jackson and James were born on Feb. 4, 2010, 34 weeks into Miranda's pregnancy.
"They were all healthy, between four and a half and five and one-half pounds," Josh said.
The babies spent three weeks in the neonatal ICU so doctors could monitor their feeding toleration. By Feb. 28, the brood arrived at home, expanding the family of three to seven.
Miranda and Josh said that it's all about the teamwork when caring for the babies, and keeping the infants on the same eat-sleep rotation is key.
"They've gained the weight they've needed to gain, and now they can sleep as long as they want at night," Miranda said.
Usually, the babies are up every three to four hours. After their morning feeding, Miranda said she bathes them, gets them dressed, gives a second feeding, changes them for the afternoon and puts them in their sleepers at night.