Ø Human chorionic gonadotropin (hCG)
hCG is an important hormone in early pregnancy. It’s produced by the placenta
after During the early weeks of pregnancy, the corpus luteum produces progesterone. After 8-12 weeks, the placenta takes over.
Progesterone stimulates
As with progesterone, the corpus luteum produces oestrogen in the early stages of pregnancy before the placenta takes over. Oestrogen is actually a collective group of similar compounds: oestrone, oestradiol, and oestriol.
Prolactin is the main hormone needed to trigger the production of breast milk. It enlarges the mammary glands to prepare for this (though as previously noted progesterone levels prevent lactation until the baby is born).
Relaxin levels are highest during the first trimester of pregnancy, but it is present throughout. It has several roles, including prohibiting contraction of the uterine muscles to prevent premature birth.
Oxytocin only appears in significant amounts towards the end of pregnancy, though it is present in lower amounts before this. Its levels rise when labour starts, triggering contractions.
Ø The corpus luteum is a temporary structure
in the ovaries which produces other key hormones during early pregnancy.
Ø hCG is also the hormone detected by
pregnancy tests. Its concentration increases from conception and peaks 8–11
weeks after. For the first few days after conception its levels are too low to
detect with pregnancy tests, but after implantation its
levels double
every 48 hours.
Ø Progesterone
Ø It also stimulates the lining to release
nutrients, providing nourishment for the early embryo. Additionally,
progesterone inhibits contraction of the smooth muscle of the uterus so that it
grows as the baby does.
Ø Progesterone levels continue to rise as
the pregnancy progresses. Along with oestrogen, it promotes the growth of
breast tissue and milk duct development. Progesterone prevents lactations
during pregnancy, which only starts when levels drop after birth. This hormone
also plays an important role in preparation for birth: it strengthens the
pelvic wall muscles required for labour.
Ø Noticing increased hair growth during
pregnancy? That’s also due to progesterone!
Ø Oestrogen
Ø Oestrogen helps the uterus grow and
maintains its lining. It supports foetal development, including the development
of organs and bodily systems. It also activates and regulates the production of
other important pregnancy hormones.
Ø Prolactin
Ø Prolactin has other roles unrelated to milk
production. It contributes to the development of the foetal lungs and brain,
and also to the mother’s immune system tolerating the foetus.
Ø Relaxin
Ø Relaxin’s name gives a clue to its more
important roles. It relaxes blood vessels, increasing blood flow to the
placenta and kidneys. This helps the mother’s body cope with the increased
demand for oxygen and nutrients from the developing baby.
Ø Relaxin also helps the mother’s body
prepare for birth. It relaxes joints in the pelvis and softens and widens the
cervix to make delivery of the baby easier.
Ø Oxytocin
Ø If labour doesn’t start naturally,
oxytocin (or synthetic equivalents) can be used to induce it.
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