Know-how: Pregnancy Hormones
And at-a-glance guide to the various hormones affecting your body through pregnancy
Posted: 8 April 2009
by Debra Stottor
From enabling you to conceive to helping your breasts produce milk, hormones play a vital role in pregnancy and birth. They’re often blamed for mood swings and tiredness, too, though the jury is still officially out on that one in spite of much circumstantial evidence. Here’s our guide to the key players, from conception on…
Luteinising Hormone and Follicle Stimulating Hormone
These hormones are inactive during pregnancy, but are vital in ensuring that you conceive in the first place. Both are produced in the pituitary gland of the brain to mature your ovaries (and a man’s testes) when you’re very young; later on, along with oestrogen and progesterone, they regulate ovulation and control your menstrual cycle
Human Chorionic Gonadotropin (hCG)
This is the hormone pregnancy tests are looking for, as it’s found in your urine and blood in increasing quantities during the first few months of pregnancy. It’s manufactured by the developing placenta soon after the fertilised egg has implanted and stimulates oestrogen and progesterone production.
This is also the hormone you can blame for morning sickness, needing to pee all the time and increased susceptibility to catching colds – it suppresses your immune function to reduce the chance that your body will reject the baby. Multiple pregnancies will bring higher levels of hCG, which is why mums of multiples tend to suffer more with morning sickness.
Levels of hCG tend to decrease around the beginning of the second trimester, when the placenta takes over production of oestrogen and progesterone, hence morning sickness usually tails off at this point in your pregnancy.
This one’s a real multi-tasker. Produced first by the ovaries, then by the placenta, oestrogen helps the uterus grow, maintains the uterine lining, increases blood circulation, and activates and regulates the production of other key hormones. It promotes the growth of your breasts, then helps develop their milk-making machinery.
For your baby it helps develop his organs and regulates bone density. It also increases blood flow, both to your mucous membranes (hence the stuffy nose, nasal congestion and headaches) and your skin – yes, this is the cause of your slightly flushed ‘glow’ (think positive, not blotches and rashes) and itchy palms.
If your skin’s feeling more sensitive, blame the oestrogen. Along with progesterone and melanocyte-stimulating hormone, it can cause hyperpigmentation, eg the darkening of the nipples and areola, and chloasma, or ‘mask of pregnancy’, where the facial skin appears darker. Your skin may be more sensitive than usual to sunlight, so take care.
So-called because of its ‘pro-gestational’ function, this is the other multifunctional pregnancy hormone. First and foremost, it keeps the placenta functioning properly and the uterine lining healthy. It also stimulates the growth of breast tissue and prevents the uterine muscles from contracting, giving your baby room to grow.
This anti-contraction function has its down-sides, though: with the help of the hormone relaxin, it can lead to many of pregnancy’s less desirable side effects, eg indigestion, heartburn, and constipation.
This hormone combo will also soften cartilage, contributing to aching hips and pubic bone towards the end of pregnancy. Progesterone is also a contributor to pregnancy gingivitis (bleeding gums), that acne you thought you’d left behind as a teenager and your increased propensity to sweating.
Human placental lactogen (hPL)
This one prepares your breasts for lactation, regardless of whether you choose to breastfeed. As well as causing the secretion of colostrum, your first milk, it affects maternal metabolism, so that you use more fatty acids and less glucose, leaving more sugar for your growing baby. It’s also linked with gestational diabetes, as it can block the action of insulin.
It may be responsible for aches and pains, heartburn and constipation, but it’s worth its weight in gold when it comes to pushing out your baby. It relaxes muscles, joints, and ligaments, particularly in the pelvis, allowing them to stretch during delivery. It also softens and lengthens the cervix and helps relax the muscles in the uterus.
This is the muscle-contracting hormone. It’s what kick-starts uterine contractions – and if labour’s going slowly, you may be given an IV injection of oxytocin to sped things up. Breastfeeding also triggers the release of oxytocin, which helps the uterus to shrink back to its normal size, and encourages the release of your breast milk.
This is the key to milk production and it’s believed to have a tranquilising effect on breastfeeding mothers. On the downside, it can stimulate the adrenal glands and lead to excessive hair growth: if this happens to you, don’t worry, your hairiness level will return to normal, usually after about six months post-birth.
Placental growth factor
One of a family of so-called angiogenic growth factors, which promote blood vessel growth, not having enough placental growth factor has been linked to preeclampsia.
Recent studies found very low levels of the hormone in women who eventually got the condition, in which blood vessels in the placenta narrow instead of widen, causing high blood pressure. The development of blood and urine tests to measure the hormone's concentration promises new techniques for early diagnosis and prevention.
Your happy hormones – do all you can to keep them flowing to help you through labour. Remember, feeling relaxed and happy in labour will probably help things go more smoothly, while stress and anxiety will block those endorphins, and may even slow down your labour. Dig out those relaxation CDs now…
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