“Balls dropping” refers to the process where the testicles move from inside the abdomen down into the scrotum. This happens primarily before birth, not during puberty as many people assume. In most babies, the testes have settled into the scrotum by about the 33rd week of pregnancy. The phrase gets used loosely to describe puberty too, when the scrotum grows larger and hangs lower, but that’s a separate process.
What Happens Before Birth
Testicles actually form inside the abdomen, near the kidneys. During fetal development, they make a slow journey downward in two stages. The first stage, called transabdominal descent, happens by the eighth week of pregnancy. During this phase, a ligament attached to the bottom of each testicle shortens and pulls it toward the groin area.
The second stage begins around the 26th week of pregnancy. This is when the testes pass through the inguinal canal, a small passageway in the lower abdominal wall, and drop into the scrotum. This stage depends on testosterone. By week 33, the testes have reached their final position in most developing babies. So for the vast majority of boys, the “dropping” is already done well before birth.
What Changes During Puberty
When people talk about balls dropping during puberty, they’re usually describing the visible changes in the scrotum and testicles that happen as a boy matures. The testicles are already in the scrotum. What actually changes is their size, the skin around them, and how low they hang.
Puberty in boys typically begins around age 11 to 12, marked by the testicles starting to grow. Before puberty, each testicle is quite small. The clinical marker for the onset of male puberty is when testicular volume reaches about 4 milliliters, which happens at a median age of 11.7 years, though it can start as early as 10 or as late as 13 or 14.
As puberty progresses, the testicles continue growing, the scrotal skin darkens, and textured ridges develop on the surface. By the end of puberty, the average adult testicle measures about 3.9 cm long and has a volume of roughly 13 milliliters. The scrotum hangs lower than it did in childhood, which is likely the origin of the “dropping” language people use. But it’s growth and loosening of tissue, not an actual descent from somewhere else in the body.
When Testicles Don’t Descend
Sometimes one or both testicles don’t complete their journey before birth. This is called cryptorchidism, and it’s more common than most people realize. About 3% of full-term baby boys are born with at least one undescended testicle. For premature babies, that number jumps to 30%, since many are born before the testes have finished their descent.
The good news is that many of these cases resolve on their own. By the time a baby reaches 6 months to a year old, the rate drops to about 1%. The testicle often finishes its descent without any help in those first months of life.
For those that don’t resolve naturally, surgery is recommended early. Most international guidelines call for the procedure to be done between 6 and 18 months of age. The surgery involves moving the testicle into the scrotum and securing it there. Early treatment matters because a testicle that stays inside the body is exposed to higher temperatures than it’s designed for, which can affect its ability to produce sperm later in life and slightly increases the risk of testicular cancer.
Retractile Testicles Are Different
Some boys and men notice that a testicle seems to “disappear” temporarily, pulling up toward the body during cold weather, exercise, or when the inner thigh is touched. This is called a retractile testicle, and it’s not the same as an undescended one. A retractile testicle lives in the scrotum normally but can be pulled upward by an overactive muscle reflex. The key difference: a retractile testicle can be gently guided back into the scrotum and will stay there without tension. An undescended testicle can’t be felt in the scrotum at all.
Retractile testicles are common in young boys and almost always resolve by puberty as the testicles grow larger and heavier. They don’t carry the same health risks as truly undescended testes and typically don’t require treatment.
Why Temperature Matters
The whole reason testicles need to be in the scrotum is temperature regulation. Sperm production requires a temperature slightly cooler than the rest of the body. The scrotum acts as a natural climate control system, hanging away from the body to stay cool and pulling closer when it’s cold. This is why undescended testicles pose a fertility risk: sitting inside the warmer abdomen impairs their ability to make healthy sperm. It’s also why the scrotum changes position throughout the day, hanging lower in warm environments and tightening up in cold ones.