"Babies, babies, babies." That's how Miranda and Josh Crawford now describe a typical day after their two sets of identical twins -- quadruplets in all -- joined their two-year-old sister in February.
After trying to get pregnant for more than a year, Miranda, 34, and Josh, 28, of Charlotte, N.C., turned to artificial insemination, and then in vitro fertilization, to have their first daughter. Doctors transferred two embryos into Miranda's uterus, and one survived. On March 17, 2009, Miranda gave birth to Baby Joslyn.
But Miranda, 34, and Josh, 28, both registered nurses, hoped to eventually expand their family over time to three or four children.
A year later, the couple sought out in vitro fertilization for a second time. Again, doctors transferred two embryos into Miranda's uterus, and, just six weeks into the pregnancy, doctors told the couple that they would be having twins.
But the ultrasound was fuzzy, and both the doctor and Miranda wanted to confirm how many babies were growing in her belly.
She returned to the hospital four days later. This time, the ultrasound was clear -- there were four hearts beating on the screen, not two.
"I was shocked, the doctor was shocked," Miranda said. "Never had that happened in his entire career."
Typically one or two embryos are inserted into a woman's uterus during one round of IVF. Even then, the patient has about a 60 percent chance of getting pregnant at all. But both embryos had split in Miranda's uterus to create two sets of identical twins.
"For a woman who is less than 35 years old, it is recommended that one or two embryos be transferred into the uterus during a fresh IVF cycle," said Dr. Jani Jensen, a physician in the department of reproductive endocrinology and infertility at Mayo Clinic. "In this case, it appears that the guidelines were correctly followed, but that lightning struck twice."
After shock, Miranda said fear stepped in. The couple was aware of the risk and complications that come with multiple births.
"The whole pregnancy was scary," Miranda said. "I wasn't sure if I was going to have a miscarriage, and I was always thinking that I could go into preterm labor at any moment."
"We took it day by day," said Josh.
Rare Situation Surprises IVF Experts
"This is certainly an unusual outcome," Jensen said. "I've never seen it happen quite like this."
Jensen said she has rarely seen embryos split, but doctors estimate that it can happen in a little more than 1 percent of IVF cycles, and slightly more if the embryos are transferred as blastocysts, or embryos that have developed longer outside the body.
"The math here is mind-boggling: the patient likely only had about a 60 percent chance of getting pregnant at all, and with that, we expect that at least half of the time when two embryos are placed in the uterus, only one will continue to develop, so even twins are more of the exception, not the rule," Jensen said.
"To have both embryos implant and both undergo the rare phenomenon of splitting is extremely unusual," Jensen continued. "There are a few reports of this happening worldwide, but overall, it's a rarity."
Only 2 percent of all pregnancies result in one set of identical twins. Dr. James Grifo, director of the NYU Fertility Center, broke down the math.