Our resident GP Dr Nicola Harrison says ‘the first thing you need to know about pregnancy is that everything medical is documented or discussed in weeks. Oddly, the first day of your last period before you got pregnant is termed Week 0 and your due date is at Week 40 – so yes, that’s actually 10 months of pregnancy!’

4 weeks (size of a poppy seed)

Congratulations! You have probably only just realised that you are pregnant with a missed period or positive urine test. You may start feeling nauseous and getting morning sickness and your breasts maybe tender. The tiny embryo consists of 3 cell layers that are the beginnings of the nervous system and brain, stomach and inner organs, and skeleton and connective tissue. The early placenta is tunneling into the womb lining looking to connect with your blood vessels. Outside the tiny embryo, the amniotic sac and fluid are forming into a protective cushion, and the yolk sac is producing blood cells to help deliver nutrients to the embryo until the placenta is fully developed and can take over supplying nutrients.

8 weeks (size of kidney bean or blueberrry)

You will probably be feeling very tired at this stage which is due to hormonal changes, in particular high levels of progesterone so ensure you get more rest than usual. Your baby’s brain is growing fast, generating about 100 new cells every minute, so the head is much larger than the body at this stage. Arms and legs are growing with webbed fingers and toes and the miniature bones are starting to harden. The kidneys are now in place and there are some early girl/boy genital differences although this won’t be visible enough to determine gender at scanning until week 16.

12 weeks (size of a lime or plum)

The top of your womb should just about be able to be felt above your pubic bone and you may be developing heartburn – again due to high levels of progesterone, which relaxes the stomach sphincter/valve causing acid to reflux upwards. Baby is almost fully formed and as the brain development has slowed down, the body development has caught up so they are the same size, covered transparent skin. The most dramatic development this week is their reflexes – your baby is kicking, stretching, sucking and clenching its fists but you won’t be aware of any of this for quite some time yet. The diaphragm is forming and the baby will hiccup regularly while this is happening. The webbing between fingers and toes has disappeared and tiny tooth buds are forming. The kidneys will start excreting urine into the bladder.

16 weeks (size of an avocado)

This is the ‘feel-good’ time of your pregnancy as hopefully any nausea has subsided, mood swings will have lessened and your skin and hair are nourished and glowing which contribute to an overall sense of wellbeing. Many women will feel their babies moving for the first time this week but others may not be conscious of it for another 4-6 weeks. These early movements can be easy to miss (especially in your first pregnancy) as they are no more than gentle flutters and can feel like gas bubbles or even popcorn popping. Don’t worry because as your baby grows there will be no mistaking their daily activities! The limbs are much more developed and the eyes and ears have almost arrived at their correct positions on baby’s head. These tiny ears can now pick up your voice and hear what you are saying. Eyebrows, lashes and hair are starting to form. The tiny heart is pumping blood around the body at a rate of about 50 pints a day.

20 weeks (size of a banana)

You are halfway through your pregnancy! The top of your womb is at the level of your belly button so there is no escaping showing. Your body needs more iron for the production of haemoglobin in your red blood cells to keep up with your expanding blood volume, as well as for your growing baby and the placenta. Some pregnancy vitamins contain iron too (e.g. Pregnacare) but to increase your dietary iron intake, try eating more red meat, prunes, green leafy vegetables and soya-based products. The baby is swallowing a lot now which is good practice for the digestive system. Meconium is being produced – a tarry black, sticky by-product of digesting amniotic fluid, intestinal juices and dead skin cells which will become the first bowel movement after birth. Vernix (a cheese-like substance covering a newborn baby’s skin) is still being produced like an expensive body cream! Permanent second teeth are forming behind the milk teeth. The genitals are now fully formed.

24 weeks (size of a corn on the cob)

Your ankles and feet may have started to swell up a little at the end of the day, especially in summer. This oedema (water retention) is caused by a combination of changes to your blood chemistry and sluggish circulation from compression in the top of the legs from the weight of the growing baby. The best cure is to elevate your legs whenever possible and lie on your side in bed, and avoid sitting or standing in one position for too long. You may be feeling a little awkward moving around but try to continue with some light exercise as this increases the circulation, and if possible wear maternity support tights and flat sensible shoes. The baby’s brain is growing quickly now, and the taste buds are continuing to develop. The lungs are developing branches of the respiratory system as well as cells that produce surfactant, a substance that will help the tiny air sacs at the end of each branch inflate after birth. It may feel that your baby is moving constantly at times and hiccups could be causing its little body to jolt.

28 weeks (size of a bag of flour or large aubergine

Welcome to the final trimester for pregnancy! Around this time, some women feel an unpleasant, restless creepy-crawly feeling in their lower legs causing an irresistible urge to move them while trying to relax or sleep. If this sensation is relieved when you move, you may have what’s known as restless legs syndrome (RLS). The cause is unknown but it is quite common in expectant mothers. Try stretching or massaging your legs and cut down on caffeine, which can make the symptoms worse. Iron supplements can sometimes help relieve RLS. You may also notice that your leg muscles cramp up now and then. These muscles are carrying extra weight and your expanding womb is putting pressure on the nerves leading to your legs. When a cramp strikes, stretching the calf muscle should give you some relief. Straighten your leg and then gently bend your toes back toward your shin. Walking for a few minutes or massaging your calf sometimes helps, too. Your baby’s major organ systems e.g. brain, lungs and liver are having the finishing touches applied to them and body fat is up to 3%. The eyes can blink, lashes have formed and with the eyesight developing, they may be able to see the light that filters in through your womb. Antibodies are being soaked up from your blood to strengthen your baby’s immune system and prepare for fighting disease after birth. Their lungs are now capable of breathing air and if birth occurs now survival is likely without the need for medical intervention.

32 weeks (size of a honeydew melon)

To accommodate you and your baby’s growing needs, your blood volume has increased 40-50% since you became pregnant and with your uterus pushing up near your diaphragm and crowding your stomach you may notice shortness of breath walking up stairs and heartburn. To help relieve any discomfort, try sleeping propped up with pillows and eating smaller more frequent meals. You may start experiencing lower back pain as your pregnancy advances, and assuming it’s not early labour, this is due to your growing womb that shifts your centre of gravity and changes your posture, and hormonal changes which loosen your joints and the ligaments that attach your pelvic bones to your spine. This can make you feel less stable and cause pain when you walk, stand and sit for long periods. Your baby’s toenails, fingernails, and real hair have formed and the skin is becoming soft and smooth. Their skeleton is still hardening from soft cartilage to bone as the many little kicks to your ribs will verify!

36 weeks (size of a large cantaloupe melon)

Hopefully, any heartburn has lessened and your breathing is easier now that the baby has moved down into your pelvis. You may feel extra pressure in the pelvic area if your baby has dropped down which can cause discomfort on walking. Braxton Hicks contractions are more frequent now in preparation for the real thing. Some mothers report that their baby’s movement slows down considerably at this stage as space becomes tight. After this week your baby will be considered full-term and should be waiting in the head-down position ready for birth. If this is not the case, an ‘external cephalic version’ may be suggested, where an Obstetrician will apply strong pressure to your abdomen to try to manipulate your baby into a head-down position.

40 weeks (size of a watermelon)

After months of anticipation, your due date rolls around, and yet you’re still pregnant! It’s a frustrating but common situation, so don’t let it get you down, your baby will be here very soon. Most of your baby’s vernix (a cheese-like substance covering their skin) is gone, 15% of their body is now made up of fat to help control body temperature after birth and your baby is fully formed and beautiful.

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