The Time Traveler's Wife

In the early 1970s, Henry DeTamble is in a car accident that kills his mother but which he survives by inadvertently time traveling back two weeks. Moments later, Henry is helped by an older version of himself who has also traveled back. Unable to control the timing or destinations of his traveling, Henry finds himself drawn to significant people, places, and events in his life but is incapable of changing events beyond the minor differences his presence creates.
In 1991, Henry meets Clare Abshire in the library where he works. She is overjoyed to see him although he is actually meeting her for the first time. Clare explains that she met Henry's future self when she was a child, and that he informed her then that they would meet in the future, which is happening at the moment. Since childhood, Henry has been Clare's best friend and visited her. Clare develops a crush with Henry, and she is upset after learning that he is married. When Clare turned 18, which is two years before their meeting at the library, the older Henry kissed Clare, leading her to realize that he is romantically involved with her and thus is her husband in the future. They begin a relationship, which is challenged by Henry's disorder. His sporadic time traveling is further complicated by the fact that he arrives at his destination completely naked. From an early age, he learned how to pick locks and to steal clothing to endure his travels. Among his getaways are many visits to young Clare. From present-day Clare's diary, he gets a list of dates when he visited her, and gives those to young Clare so that she can be waiting for him with clothes. Falling in love, Henry and Clare eventually marry, though he actually time travels away before the ceremony and an older version of himself arrives in time to step in, though his altered appearance confuses guests.
Henry's disappearances allow him to win the lottery by having the numbers in advance, but his disorder takes a toll on his relationship with Clare. It also makes having a child with Clare seemingly impossible, as Henry's genes cause their unborn fetuses to time travel. They seek a renowned doctor's help, but after numerous similar miscarriages, Henry has a secret vasectomy to end their suffering. However, soon after, Clare gets pregnant one last time â by a visiting younger version of Henry â and carries the baby full-term. Before the child is born, Henry travels forward in time and happily meets their pre-teen daughter, Alba; she tells him that she is a time traveler, too, but has increasing control over when and where she travels. Alba tells Henry that he will die when she is five years old, a fact that Henry subsequently hides from Clare. Alba's pre-teen self, who ultimately tries to prepare her younger self for Henryâs death, visits young Alba sporadically. Clare is devastated to discover what is soon to come. Later, Henry time travels and is accidentally shot by Clare's father who is hunting elk. Henry returns in time to die in Clare's arms. Some years later, a younger Henry visits Alba and Clare, giving Clare hope that he will visit again, though he tells her not to spend her life waiting for him, hoping this encounter would provide a proper closure for both Clare and Alba.

Question: What does Henry have done in secret to end their suffering?
Answer: Vasectomy