Hormonal changes postpartum

• human placental lactogen - reaches undetectable levels in the first day postpartum.
• human chorionic gonadotrophin - falls to very low levels by the 7th day.
• progesterone - falls to below luteal phase levels by the 3rd day.
• oestrogen - follicular levels are reached by non-lactating women by about the 21st day. This process is delayed in lactating women.
• prolactin - there is a gradual decrease in non-lactating women over the first 2 weeks. In lactating women the decline is more gradual and occurs over several months of lactation. Release of prolactin is increased by nipple stimulation. Prolactin has been associated with the relative refractoriness of the puerperal ovary. This effect appears to be due to the prolactin causing a disturbance in the release of leutinizing hormone by the anterior pituitary, and not because of direct effects of prolactin at the ovary.
• thyroid-stimulating hormone - are all very low in all women during the first 2 weeks postpartum. There is slow increase to the levels that occur in the follicular phase during the 3rd week.
  
  

There are significant differences in the time of onset of menstruation between lactating and non-lactating women. The first menses are usually preceded by an anovulatory cycle. Most non-lactating women have ovulated by 90 days post-delivery.