Twins foetal development week by week

Every baby develops at slightly different rates, so please use the following information as a guide only.

0-8 weeks

Foetal developmentBy the end of the second month, the embryos will be approximately 1.5cm long and will start to look baby like.The hearts have begun beating and can be seen on an ultrasound scan.The eyes develop and become pigmented. Arms, feet, ears and  tongues have formed and all the body’s major organs are there. They make spontaneous movements, though it is too early to feel them.

 8-12 weeks

The babies/embryo’s are now foetus’s. They are approximately 6.5-7.5cm long and weigh around 20g each. The foetus’s head is now sitting on a neck, but is still very large in comparison to the rest of the body.Their eyes are moving closer together, the eyelids will close and not reopen until week 28. Their ears are moving into position on the side of their heads. There are nails on fingers and toes. Taste buds have now developed. They are making urine and excreting it into the amniotic fluid.The external genitalia are developed enough to tell the sex of the babies. A heartbeat can be heard with a doppler.

12-16 weeks

By the end of the fourth month the babies will weigh around 85g each and be around 16cm long. Their brains are fully developed. Their bodies now grow faster than their heads. There is now hair on their bodyies called lanugo which is temporary. They have fingerprints, they can suck their thumbs and swallow amniotic fluid as well as pass urine. They also practice breathing movements. Their arms and legs are now moving so you may feel some kicks soon! Eyebrows and eyelashes have appeared.

16-20 weeks

By now the babies will be around 25cm long. They can hear sound, so if you talk or sing to them it helps them recognise your voice when they are born. Their skin will begin to be covered in a whitish greasy substance called vernix. This protects their skin from the amniotic fluid and makes them slippery at birth. The babies are becoming much more active and will have periods of wakefulness and sleep. Most mums feel their babies first movements around 18-22weeks.

20-24 weeks

The babies skin appears wrinkled as they still need to gain weight. They weigh approximately 595g each. Their eyes are formed and lips are distinct. Tooth buds appear under the gum line. They now have a hand and startle reflex. They are practicing breathing movements, getting ready for birth. If twins are born before 24 weeks they have a small chance of survival, but their chance of survival increases rapidly after 26 weeks. At this stage every day inside the uterus counts.

24-28 weeks

By 28 weeks your babies will now measure around 35cm and weigh around 2lb4oz/1kg each. Their eyes open and close and by the end of the seventh month most babies react to sound. Their brains develop rapidly during this time. They may turn their heads towards a bright light. Their growth in length will soon slow down but they will continue to gain weight. Each baby is surrounded by a litre of amniotic fluid, however this will decrease as the babies grow.

28-32 weeks

The babies are looking more proportional now  and now weigh around 3lb11oz/1.7kg and measure around 40cm in length. The babies sleep around 90-95% of the day. Lanugo has started to disappear. Their skin is pink and smooth. Brain growth in the next two months is great. Their lungs are still immature, but are beginning to function, as rhythmic breathing occurs. Babies born now have a very good chance of survival. The babies should be starting to get ready for their birth by getting into position, turning upside down.

32-36 weeks

At this stage one of the babies will gradually move down into the pelvic cavity getting ready for the birth. they weigh approximately 5lb2oz/2.3kg each and measure 45cm in length. Most of the lanugo and vernix has disappeared. The babies swallow this and other secretions, store them in the bowel and will pass this as their first bowel movement (black) called meconium. Their organs are now fully developed, although the lungs are the last to mature around 37 weeks. Around half of twins are born by 36 weeks.

36-40 weeks

A large proportion of twins are already born by now. Twins are considered full term from 37 weeks. They are now ready to meet you!