What does pregnancy do to your hormone balance in the long term?

Pregnancy thoroughly disrupts the hormonal system, and not all of those changes disappear once the baby has arrived. A well-researched example is the uterine lining: this tissue responds strongly to oestrogen and progesterone, which drive cell division and maturation. That holds true both during and after pregnancy, and has been established in laboratory models of human tissue.

A hormone many people know as the 'cuddle hormone' is oxytocin. During labour it is released in increasingly rapid waves. There are indications that the labour period, through changes in how genes are read, may have a lasting effect on how the body produces and processes oxytocin, but this remains suggestive for now. Definitive evidence in humans is still lacking.

More concrete and better supported is the link between gestational diabetes and type 2 diabetes later in life. Gestational diabetes temporarily disrupts the regulation of insulin and blood sugar; women who experience this turn out to carry a clearly elevated risk of developing permanent diabetes afterwards. This is a reason to have your blood sugar checked after pregnancy if you have had gestational diabetes.

The calcium balance and the parathyroid glands also change measurably during pregnancy and breastfeeding. The body adjusts its calcium processing to meet both its own needs and those of the baby. For most women this returns to normal on its own after pregnancy, but in women with a pre-existing parathyroid condition this can complicate diagnosis and treatment.

Finally: when a baby is at risk of being born too early (around 34 to 36 weeks), mothers are sometimes given a stress hormone (betamethasone) to help mature the baby's lungs. This helps in the short term, but the baby may develop low blood sugar as a result. Reassuringly, a large-scale follow-up measurement showed that the brain development of children at age six was not affected by this.