Understanding Pregnancy Hormones

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Just found out that you’re pregnant? You may find yourself suddenly experiencing a whirlwind of emotions or insatiable food cravings. Don’t question your sanity – it’s just pregnancy hormones at work. Here’s what to expect when you’re expecting.




Pregnancy. Definitely a gift to be cherished, but also a journey of many ups and downs. Right from the beginning of conception, you start to notice numerous physical changes happening to your body, and it’s not just the baby bump. You may also be wondering why you’re in tears one moment and laughing uncontrollably the next, even though you’ve always been a fairly cool-headed person. Well, you can blame (or thank, as you’ll soon be finding out) your pregnancy hormones. We explain the mechanics of what’s going on inside, identifying the key hormones at play and how they affect your mind and body. 


The Start of It All

In the early stage of pregnancy, the hormone human chorionic gonadotropin or hCG is released by the fertilised egg. You could say it’s the bearer of good news, as the presence of this hormone in urine signals the start of pregnancy. In fact, it’s responsible for the little plus sign on home pregnancy kits. hCG may be found in urine as early as seven to nine days after fertilisation, and kick starts the production of other essential pregnancy hormones. Through hCG, the corpus luteum (what’s left behind of the egg follicle after ovulation) is stimulated to release the hormones oestrogen and progesterone, and this carries on for the first ten weeks of pregnancy until the placenta takes over.



Unfortunately, with its beneficial functions comes the inevitable downside. 

Nausea and vomiting, also known as the big baddie morning sickness, 

unleashes its reign of terror as hCG levels escalate during the first trimester.

hCG also increases the blood supply to your pelvis, which makes for a hyperactive bladder. 

This explains your constant trip to the bathroom in the middle of the night.



The Big Players: Growth and Development

hCG leads to the production of oestrogen, a hormone that increases steadily until birth. Oestrogen enables the uterus to grow and is paramount to the development of your baby’s various organs. Key in controlling the production of other hormones, it also ensures that your placenta is doing its job. Given its vital role, this hormone is thankfully not in short supply. Levels of oestrogen are approximately 100 times higher in pregnancy than during your period!


Additionally, oestrogen affects levels of neurotransmitters, the brain chemicals that regulate mood. This makes it guilty of propelling your emotional roller coaster and causing your mood to switch from a two to a ten in a heartbeat or vice versa. And the increase in appetite that makes you rummage through the fridge at 10pm looking for a bite, or random food cravings where you insist on having hamburgers for dinner three days in a row? Blame it on oestrogen as well. Other side effects are a decreased libido, heightened sense of smell, headaches, and cervical and vaginal mucus production.


Similar to oestrogen, the hormone progesterone is present in higher levels until the first trimester concludes. Equally indispensable, it facilitates the baby’s growth in the womb by preventing uterine contractions and suppresses the immune system so your body doesn’t reject the foetus. However, this results in a greater susceptibility to colds and the flu, so be mindful of what medication you take during this period so as not to harm your baby. A relaxation of smooth muscles in the lower intestine and bowels also occurs. Cue the much bemoaned tummy troubles such as bloating, indigestion and constipation.


Don’t panic if you look in the mirror too...progesterone may lead to acne breakouts and the growth of more bodily hair around the breasts and abdomen, but these tend to go away as hormone levels dip. Progesterone’s saving grace? Its tranquillising effect, reducing stress and helping you fall asleep faster.


Other Key Players

Feeling pain and discomfort in your hips and lower back? That’s the work of relaxin. True to its name, it relaxes a pregnant women’s muscles, joints and ligaments to give the baby space. It also answers the age-old question of why pregnant women waddle.



If you notice yourself becoming clumsier or an unsteadiness in your walk,

that’s not just your bulging belly, but relaxin at work.

At its peak in the second trimester,

relaxin contributes to the dreaded heartburn,

as the muscle that prevents stomach acid from flowing back into your oesophagus

becomes more relaxed than usual.



Thankfully, relaxin redeems itself by enabling your arteries to handle additional blood volume, keeping blood pressure at bay. What’s more, it eases the baby's passage through the birth canal right before birth.


Present for most of the pregnancy, oxytocin is most acutely felt during the last trimester of pregnancy. It’s a hormone that most mothers would welcome as well.  Associated with feelings of bonding and motherhood, a surge in oxytocin levels causes your excitement to shoot through the roof in the weeks leading up to childbirth. You become even more aware that you will be cradling a little bundle of joy in no time! This is also when the nesting phase may kick in, where you feel the inexplicable urge to make extra household preparations for the arrival of your newborn. Oxytocin levels spike further as labour commences, causing repeated womb contractions. After delivery, oxytocin enables the uterus to return to its normal size and stimulates milk production in your nipples for breastfeeding. 


Prolactin also has a part to play in the process of milk production. This hormone operates by developing breast glands and altering breast tissue structure to gear your body up for breastfeeding. Breast tenderness and swelling are usually experienced, so don’t be surprised if you find yourself shopping for new bras two sizes up. Prolactin increases up to twenty times more than pre-pregnancy levels, remaining high until weaning occurs. Like progesterone, it tends to have a tranquillising effect and is sometimes referred to as the “mothering” hormone. Ironically, it can even work against conceiving. Pre-pregnancy, abnormally high levels are linked to infertility as prolactin inhibits other hormones that trigger ovulation.


Braving the Emotional Roller Coaster

Rest assured – your hormones begin to normalise immediately after the placenta’s delivery, and are back to pre-pregnancy levels sooner that you know it. Aside from all the negativity in terms of physical discomfort and mood swings, the functioning of these hormones is a telling sign that your baby is growing healthily inside, so don’t be overly anxious or treat these issues as added cause for concern. The female body is amazingly resilient, and hormones reflect its ability to withstand the many demands brought on by pregnancy.

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