UPPER WEST SIDE — Pfizer executive Jonathan Sporn says that words couldn't describe the joy he felt when his son was born in July.
For a doctor whose work life involved lab coats, test tubes and ground-breaking research, fatherhood felt natural. He delighted in reading and playing make-believe with the infant. He embraced changing diapers and enjoyed taking the baby for check-ups with the pediatrician.
Sporn, 54, says he did all the dad duties — except provide the sperm.
And that sticking point, he says, has led to a legal nightmare with him desperately trying to reunite with his son.
On New Year's Day, his live-in girlfriend — the boy's biological mom — committed suicide. Since then, child welfare officials have kept the 6-month-old in their custody.
The separation led Sporn to petition the Manhattan Supreme Court on Tuesday for the return of the kid, claiming he has been "the only father the child has ever known."
"I have been forced to cope with the unspeakable tragedy of losing the mother of my only child to suicide, but now I have been forced headfirst into a legal conundrum, making it necessary for me to seek the intervention of the court to regain custody of my son," Sporn said in the petition.
"I cannot change history, [the mother] is gone and while that is unbearable in and of itself, the fact that my son is being cared for by strangers and away from me, his dad, is equally unendurable," he added.
Sporn's heart-wrenching petition chronicles his three-year romance with LeAnn Leutner, a brilliant but troubled Yale Law School grad and close friend of Manhattan Borough President Scott Stringer. It also details how the couple went to great lengths to conceive until finally choosing an anonymous sperm donor for in-vitro fertilization.
Sporn said he and Leutner, 40, met in March 2010, and the two "had an undeniable chemistry and began dating immediately."
Both were divorced and both had achieved great success in their careers.
Sporn, a physician, is a director in clinical research and development at the pharmaceutical giant, earning more than $275,000, according to the petition.
Leutner was a lawyer at white-shoe firm Simpson, Thatcher and Bartlett LLP. She was also an active member of the Democratic party and had served as Stringer's campaign treasurer.
Sporn and Leutner quickly became inseparable, spending every weekend together and taking trips to Disney World and Maine, according to the petition.
The two concocted their own private jokes and pet names for one another. Sporn called her "dollzy," and she referred to him as "boysee."
By December 2010, Leutner had moved into Sporn's Riverside Drive apartment in the Upper West Side.
"As our love for one another deepened, it was obvious that I wanted to spend eternity with LeAnn, to have a family with her," Sporn said.
The couple enthusiastically spoke of having children, and Leutner, who was nearing 40 at the time, wanted to begin trying to conceive immediately, according to the petition.
When Leutner didn't get pregnant naturally, the two went to an IVF clinic at New York University. She began a grueling regimen of hormone injections and egg-retrieval classes. But all of the implanted embryos failed to take.
Leutner considered obtaining an egg donor, but Sporn encouraged her to keep trying because he wanted the baby to be biologically hers, the petition says.
After three failed cycles, they tried a donor sperm that Sporn had chosen, and it took.
"To LeAnn's surprise and our mutual delight, it finally worked and LeAnn became pregnant," Sporn said.
During the pregnancy, Sporn said he assisted Leutner with progesterone shots, accompanied her to her obstetrician appointments, and helped her pick out furniture for the nursery, the petition says.
When the child was born in July, Sporn and Leutner were elated.
"It felt surprisingly natural to be a father and LeAnn and others commented on how good I was at it," Sporn said.
Shortly after the birth, Leutner suffered post-partum depression, the petition says. She had a history of mental illness, including mood problems and dissociative states. During her pregnancy, she had also stopped taking the anti-depressant Prozac, according to the petition.
Her state became critical around Thanksgiving, when she tried to jump out of a window after one day back in her office, the petition said. Sporn and Scott Stringer had her admitted at New York-Presbyterian hospital in Westchester after the attempt on her life.
Her deteriorating condition made him the primary caregiver to the child, Sporn said.
"During this time, I was a hands on dad, learning as I went, and falling deeper and deeper in love with this child," he said. "I looked forward to his cries in the night just to have another opportunity to hold this child in my arms and soothe him back to sleep."
After 10 days in the hospital, Leutner returned home. But a few days later, she tried to jump down the shaft of a stairwell on the 19th floor. Sporn again had her admitted to a hospital.
"I was in fear of losing my partner, my best friend and the mother our child," he said.
Leutner quickly grew restless and wanted to leave the hospital, according to the petition. Sporn says that, unbeknownst to him, a mutual friend helped her get discharged on Dec. 17 and they went to New Jersey with the child.
He claims Leutner's mental state "was clouded and she was extremely depressed." It was during this time, he says, that she decided to get her own apartment. Two days after securing the apartment, she jumped to her death from the 14th story of her building.
Sporn said he only learned of what happened to Leutner from New Jersey Child Protective Services. Officials called him to say the mutual friend had kept the baby in New Jersey at the time of Leutner's death and they now had custody.
Sporn's lawyer did not return a call for comment.
The petition does not say if the child's birth certificate lists Sporn as the father. But the petition says that Leutner had executed a formal document naming Sporn as the baby's guardian.
Before her death, she was also completing paperwork to change the baby's last name to Leutner-Sporn, according to the petition.
"I respectfully submit that from the time [the baby] was conceived he was my son," Sporn said.
"I spent countless hours devoted to his prenatal care, reading about fatherhood, attending doctors appointments, reading to him in the womb, and dwelling on the new life that was about to enter mine."