Often there are more of those questions than aspiring parents realize. What happens if one or both parents die before the baby is born? What if one or both parents die before a baby is conceived? Would you want your husband or parents to use a surrogate to create a baby with your eggs or embryos? Would you want your wife or girlfriend to use your sperm? Would you want any of those children to share in your wealth? What if you and your partner separate before your reproductive efforts come to fruition? Would you want your ex-wife to use your sperm to create your heirs, and would you acknowledge them? “You need to be as explicit as possible in these situations,” advises Northwestern’s Shapo, who has written articles on the issue of assisted reproduction and inheritance.

Racanelli is working with a family that is already wrestling with some of these questions. In their case, a father created a trust for his two sons, only one of whom had children when the father died. If the other son died without any offspring, then his brother’s children would eventually receive all assets in the trust. One son indeed died childless, but a year later, his wife became pregnant with sperm he had earlier frozen. He did not make clear whether he wanted his sperm to be used posthumously or if he wanted to recognize a resulting child as his heir. Now the family is forced to decide. “Was the sperm intended for that, and is that child his heir?” Racanelli asks.

States have split over whether posthumously conceived children are heirs for the purpose of social security and other benefits. There is no clear answer to these questions as of yet. If a family includes a child in his father’s estate and it is later judged they did so improperly, it could trigger unintended gift and estate taxes, Racanelli notes. Moreover, given the dynamic nature of fertility laws, trustees might make a decision today that can later be challenged. “They might be sued by the rest of the family,” points out Gail Cohen, general trust council for Fiduciary Trust International in New York.

Even in cases when families do not foresee becoming adversarial, Racanelli notes, they should prepare for the evolving environment of this legal field to force trustees to take these cases to court for a clear ruling. “This is the kind of thing that can cause family wealth to erode,” she explains. Particularly if there are disgruntled family members, but even if there are not, lawyer and court fees can quickly add up, while distracted trustees will utilize precious resources preparing legal documents instead of managing investments.

In addition, if courts do make way for these posthumously born children to be considered heirs, it could delay the settlement of an estate for years. If a man leaves behind sperm that’s viable for 10 years, you might have to leave the estate open for that long, or until the wife or partner makes it definitively clear that she will not seek to use that sperm to become pregnant, Racanelli notes.

So advisors are urging their clients to spell out their wishes clearly. Spouses who face fertility issues in a second marriage, and who have children from a prior marriage to consider, seem to be more likely than others to be proactive. WealthPlan’s Browning has a client who recently came to him to set things in order before conceiving a child with his second wife, in vitro, using his sperm. “He wanted to make sure [his] kids from the prior marriage received their fair share,” Browning explains. “His concern was that if they divorced or if he died, she might get pregnant again to get a larger piece of the pie, so to speak.” Browning and his client made certain his trust documents identified his children as those from his first marriage and one from the second marriage. “It specifically excludes any children born after this one,” Browning says.

Such a move might seem cynical or even unduly harsh, but given today’s new reproductive realities, it is prudent. “You want to avoid giving people room to challenge your intent,” Racanelli says.

Eileen P. Gunn is a Brooklyn-based writer who has written about personal finance, executive careers and real estate, among many other topics.

Illustration by Isabelle Arsenault.