Pregnancy: What effects does it have on hair?

Many pregnant women notice an improvement in the appearance and texture of their hair. This improvement is correlated with the increased production of oestrogen and progesterone in the body. Indeed, oestrogens are capable of binding to certain specific receptors present in the scalp that have an affinity for these hormones. These receptors trigger a cascade of reactions, ultimately leading to a speeding up of the anagen phase. This phase corresponds to the period of hair growth in the hair cycle. Progesterone, on the other hand, is responsible for the inhibition of the activity of 5-alpha reductase, an enzyme modulating the conversion of testosterone into dihydrotestosterone (DHT). However, DHT acts at the level of hair follicles by shortening the lifespan of hair and accelerating hair cycles. This is why pregnant women often notice faster hair growth.

Progesterone is capable of binding to certain receptors belonging to the nuclear receptor family of the sebaceous glands, organs present throughout the skin, including the scalp. This binding triggers several biological mechanisms, among which the activation of Protein Kinase C (PCK). This in turn stimulates sebum production by increasing the activity of Phospholipase A2 (PLA2), an enzyme that breaks down membrane phospholipids into free fatty acids and lysophospholipids, precursors of sebum. As a result, women tend to find their hair shinier during pregnancy.

However, it's important to note that we cannot make generalisations. Some pregnant women notice no changes to their hair. Sensitivity to hormones varies from person to person, as does the amount of hormones produced.