The surrogate became pregnant but said she wanted to keep the child and disappeared. “We paid 30,000 yuan,” about $5,000, “as a down payment,” Ms. Zuo said. “And we got nothing and have no way to find the woman.”

Here in Wuhan, Baby Plan offers a more expensive, but at times grimly controlled, program. Chinese couples fly to Thailand, where surrogacy is legal, to donate their sperm and egg. A Chinese surrogate is flown there, too, and receives the implant. The three return to China and the surrogate is installed in a private apartment with a full-time assistant. To make sure she does not get ideas about fleeing with the customer’s fetus, she is cut off from her family and receives daily visits from a psychological counselor, Mr. Huang said.

If all goes well, the baby is born at a private clinic, which Mr. Huang says has an agreement with Baby Plan to accept the couple’s identity papers, legally registering the child as their own. Often, the couple never meet the surrogate. If the fertilization works on the first try, Baby Plan makes a profit of $24,000, Mr. Huang estimates, the same amount the surrogate mother makes.

“The baby is guaranteed, as well as a DNA check,” Mr. Huang said. “Otherwise you don’t pay.”

One Baby Plan client is a 49-year-old professional from Shanghai who asked to be known only by her family name, Zhang. Ms. Zhang’s 18-year-old daughter committed suicide in 2012. Because of China’s single-child policy, she was the only offspring of Ms. Zhang and her husband. After a year and extensive counseling, the couple decided that they could heal only if they had another child. A medical test, however, showed that Ms. Zhang’s eggs were probably too old to be fertilized. Ms. Zhang said she suggested to her husband that they use another woman’s egg.

“At least with his sperm it will look a bit like her,” Ms. Zhang said of her dead daughter, her hands shaking. “It will be a bit like having my child back — half the blood will be hers, so my heart will be soothed.”

Ms. Zhang’s surrogate is four months pregnant and she recently visited the woman. “It’s not easy for them either,” she said.