Expansion
hCG early from trophoblast, then progesterone and oestrogen from the placenta
Expansion
- hCG: from syncytiotrophoblast, detectable about 8 days after conception, peaking at 8 to 10 weeks then falling. It maintains the corpus luteum, and its alpha subunit resembles TSH, which is why very high levels in hyperemesis or molar pregnancy cause biochemical hyperthyroidism
- Progesterone: from the corpus luteum until the luteoplacental shift at 8 to 10 weeks, then the placenta. Maintains the endometrium, relaxes smooth muscle (contributing to reflux, constipation, ureteric dilatation and venous stasis) and stimulates respiration
- Oestrogen: mainly oestriol, requiring fetal adrenal precursors, so it reflects fetal wellbeing. Promotes uterine growth and breast duct development
- Human placental lactogen: anti-insulin, mobilising fatty acids and sparing glucose for the fetus. The main cause of gestational diabetes
- Prolactin: rises through pregnancy but lactation is blocked by high progesterone, which is why milk production begins only after delivery of the placenta
- Relaxin: ligamentous laxity