Twin Pregnancy Week By Week
0 to 4 weeks
During these early weeks, unless you have an inkling you may be having twins, you will likely be unaware that you have two growing babies. Most commonly, confirmation by ultrasound is the ultimate answer. Although, many twin moms will experience heightened pregnancy symptoms, none of them are definitive of twins.
4 to 8 weeks
your twin embryos will each grow from around 3/500 of an inch to around 1 inch long and weigh less than an ounce each. Their brains, bladders, kidneys, livers, spines, reproductive organs, arms and legs are all starting to develop, as well. Around 6 weeks, twins are usually visible via ultrasound.
8 to 12 weeks
the last month representing the embryonic stage, your twins are swiftly progressing in their development They will have quadrupled in both length and weight. Even during these early weeks, it's fascinating to know that their teeny nail beds are starting to form along with the buds for their baby teeth. They are distinctly human at this point with the most miniscule fingers, toes, genitalia, and eyelids!
12 to 16 weeks
Your twins are still growing at a fast pace during this month. They have also graduated to the fetus stage, although, many of us twin moms are already fondly referring to them as "Baby A" and "Baby B". The kidneys are beginning to function and by the 16th week water in their stomachs and urine in their bladders may be detected via ultrasound. They are actually contributing to the amniotic fluid by swallowing it and then expelling it back out through urination...Their first contribution to their environment! They will measure close to 6 whole inches by the end of the month. There is more movement going on too, though unlikely strong enough to be felt by the mother.
16 to 20 weeks
Each fetus now appears as a fully formed, tiny baby (about 8 inches or so by the 20th week). At this point, the brain is the only component that shall continuously develop throughout pregnancy. Your twins will spend the rest of their stay in the womb growing, and growing, and growing! They will be exhibiting more coordinated movements at this time, and many believe that twins are now aware of each other as well.
20 to 24 weeks
By the end of this stage, each twin will weigh in at about a pound-and-a-half and measure around 12 inches. They are covered in downy hair called lanugo, as well as a cheesy coating of vernix (thought to protect the delicate new skin). They are typically seen in the traditional fetal position via ultrasound. Theyare developing a smidgen of fat under their otherwise red, wrinkled skin and their fingerprints and footprints have formed too.
24 to 28 weeks
It is during this crucial month that the twins growing inside you will cross the threshold of viability. Because of the remarkable advances in care for premature infants, their rate of survival has gone up considerably when they reach 28 weeks. They will double their weight this month and grow to approximately 15 inches in length. Every feature is becoming more distinct as hair continues to grow, more fat accumulates under tht skin, and eyelids become unfused. They will each have their own individual sleep cycle also.
28 to 32 weeks
Your twins are still progressing at a rate comparable to singletons at this point. They are around 4 pounds each by week 32 and approximately 16 inches. They have gained more fat which has helped to fill out their wrinkled skin. Their skeletal structure is complete, although the bones will remain soft and flexible until the last eight weeks when they start to store calcium and iron. The size of the body is catching up in relation to the size of the head, which seemed disproportionately larger until now.
32 to 36 weeks
Your twins are in pretty tight quarters at this point. They are approaching five pounds each and about 18 or so inches in length. Their weight gain will now slow a little in comparison to a singleton, but their lung development will charge ahead in preparation for that first breath. Their motor development is becoming more and more complex and much less reflexive. They also have full grown fingernails and toenails. The placenta(s) is still providing them with lots of nourishment to help them gain that all important final layer of fat.
36 to 40 weeks
Your developing twins are becoming larger and stronger as they approach what most doctors consider full term for a twin pregnancy, 38 weeks. They will have very little, if any, space to squirm around. They are now putting a tremendous load on the placenta(s) and will likely be monitored by your doctor weekly at this stage. Most of the downy hair that developed on their bodies (lanugo) has disappeared as the storing of body fat continues. Twins born around this time will generally have birth weights slightly lower than that of singletons.
