The time between two pregnancies may be an important factor not only for the health of the unborn child, but also for the rate at which the mother's body ages.
A new scientific review by researchers at Harvard Medical School suggests that too short a gap between pregnancies may interrupt natural recovery after childbirth and contribute to the accumulation of changes associated with biological aging.
The analysis, published on October 22, 2026 in the scientific journal Trends in Endocrinology & Metabolism, was done by Stephen Albright and Jesse Poganick of Brigham and Women's Hospital and Harvard Medical School. Scientists summarize results from previous studies and offer a new explanation for the link between reproductive history and long-term health in women.
The hypothesis is based on biological age, which reflects the state of cells and tissues and does not always coincide with a person's actual age. One way to measure it is through so-called epigenetic clocks, which analyze chemical changes in DNA associated with aging processes.
Previous research has shown that pregnancy temporarily increases some indicators of biological age. A Yale University study published in 2024 in Cell Metabolism found an increase of approximately two biological years within about 20 weeks of pregnancy. Just three months after birth, however, scientists observed a significant decrease in the same indicators, indicating that some of the changes are reversible.
It is this recovery period that attracts the attention of the authors of the new review. According to them, the body may need months, and sometimes more than a year, to restore some of its biological indicators. The process likely depends on multiple factors, including pre-pregnancy weight, breastfeeding, sleep, stress, and individual health.
If the next pregnancy occurs before recovery is complete, the body may be subjected to a new physiological load. In consecutive pregnancies with short intervals, these effects could potentially accumulate.
The researchers identify the interval between pregnancies as a possible “missing variable“, which could explain why in some population studies a higher number of births is associated with increased risk for maternal health, while in others such a relationship is not observed.
However, the authors emphasize that this is currently a scientific hypothesis, not a proven cause-and-effect relationship. It has not been established that a short interval between pregnancies necessarily leads to permanent accelerated aging or shortened lifespan. Long-term studies that follow women before, during, and after several consecutive pregnancies are needed to confirm this assumption.
The topic also has direct practical implications. The World Health Organization recommends waiting at least 24 months after giving birth before attempting another pregnancy to limit the risks to the mother and child.
The American College of Obstetricians and Gynecologists (ACOG) advises women to avoid a new pregnancy in the first six months after giving birth and to discuss the risks of an interval of less than 18 months with a doctor. Short intervals are associated with a higher likelihood of premature birth and low birth weight, and in certain circumstances after a previous cesarean section, with an increased risk of uterine rupture.
Specialists specify that the recommendations refer to the time between birth and the next conception, not between two births. The optimal interval should be assessed on an individual basis, especially for women over 35, those with difficulty conceiving, or those with specific medical circumstances.
The new review puts the issue of postpartum recovery in a broader context. If the link to biological aging is confirmed, the time between pregnancies could be an important factor not only for the outcome of the next pregnancy, but also for women's health decades later.