Your pregnancy in weeks (gestational age)

You can roughly work out when your baby is due using the date of the first day of your last period (LMP). After your first ultrasound scan your due date may change a little; this is quite common.

5 weeks:

By the end of the 5th week after fertilisation or 7 weeks gestational age, the baby is known as an “embryo” and is approximately 12.7 millimetres long. The brain, spinal cord, and nervous system are more developed. The head has increased in size, and the nostrils, lips, and tongue are visible. The limb buds have grown into arms and legs.

6 weeks:

By the end of the 6th week after fertilisation or 8 weeks gestational age, the embryo is approximately 22 millimetres long. The head is quite large in comparison to the trunk. External ears form elevations on either side of the head. A skeleton made of cartilage, not real bone, has appeared; and a tail is apparent at the end of the spinal cord. Fingers and toes have formed.

9 weeks:

By the end of the 9th week after fertilisation or 11 weeks gestational age, the baby looks more human. It measures almost 5 centimetres in length and weighs approximately 4 grams. Most of the major structures have formed. Development now consists of the growth and maturing of present structures. The scrotum has appeared, as have fingernails, toenails and hair follicles.

12 weeks:

By the end of the 3rd lunar month, or 12 weeks gestational age, the baby is over 2.5 inches in length and weighs 7 grams. You may hear the baby being referred to as a “fetus” by healthcare professionals. The face is well developed, with the eyelids present, though fused. The baby can move the muscles of his face to squint, purse his lips, and open his mouth. The arms, hands, fingers, legs, feet, and toes are fully developed. The external genitalia show definite signs of male or female sex. The baby can make a fist and kick with his feet, although you won’t be able to feel it yet. The uterus can be felt just above the woman’s pubic bone.

16 weeks:

By the end of the 4th lunar month, or 16 weeks gestational age, the baby is almost 12 centimetres long and weighs 100 grams. The essential body systems are now present; most of the remaining changes will be in size. To facilitate this growth, the placenta is also growing rapidly. The baby’s skin is getting thicker and less transparent, and is forming several layers. Eyebrows and eyelashes are evident. The baby may suck his thumb, and he may swallow amniotic fluid and then pass it out as urine. Meconium, the baby’s first bowel movement, is beginning to collect in his intestinal tract. Some women feel the first faint fluttering movements between their pubic bone and navel. These movements are often initially confused with gas, but the feeling is known as “quickening”, the earliest felt movements of a baby. Usually, quickening is first perceived between the 16th and 18th weeks, although this can vary from person to person.

24 weeks:

By the end of the 6th lunar month, or 24 weeks gestational age, the baby is almost 28 centimetres and weighs 500 grams. Vernix caseosa, a cheese-like coating that protects the baby’s skin from its watery environment, has developed. The eyes are open, and the fetus can hear. Fingerprints and footprints have formed. By this time you should be able to feel regular fluttering movements. You should inform your midwife if you have not felt any movements by 24 weeks.

28 weeks:

By the end of the 7th lunar month, or 28 weeks gestational age, the baby is close to 33 centimetres long and weighs about 900 grams. The eyes can perceive light, and the baby can hear, smell, taste, and respond to touch. The baby has definite awake and sleep periods.

32 weeks:

By the end of the eighth lunar month, or 32 weeks gestational age, the average baby is 38 centimetres long and weighs 1,500 grams or more. The skin is still red but is less wrinkled, and the fingernails are long.

36 weeks:

By the end of the 9th lunar month, or 36 weeks gestational age, the baby is almost 43 centimetres long and weighs between 2160 grams and 2,500 grams. During the last 2 months of gestation, the baby gains about 25 grams of weight a day. This weight gain is important because it provides the baby with a layer of fat under his skin that will help keep his body temperature constant outside the uterus. The skin has become smoother, and the redness has faded to pink. Most of the lanugo has dropped off, remaining only on the arms and shoulders. (Lanugo is the first hair that grows out of your baby’s hair follicles while they are still developing in the womb.) The lungs are maturing getting ready for respiration.

40 weeks:

By the end of the tenth lunar month, or 40 weeks gestational age, the baby’s brain has greatly increased in number of cells. This growth will continue for the first 5 to 6 months after birth. By now, 96% of all babies are positioned head down. During the final 2 to 4 weeks of gestation, the head or other presenting part settles down into the top of the woman’s pelvis. During his last lunar month, the baby gains around 200 grams per week and, by the fortieth week, is an average of 50 centimetres in length and averaging 3 to 3.5 kilograms in weight. The baby is ready to be born.

42 weeks:

By the time the baby reaches 42 weeks gestation they are considered postmature. It means a baby’s skin may be temporarily dry, cracked, peeling, loose, or wrinkled because the protective cheesy vernix was shed weeks ago. He may have longer finger and toenails and longer hair. Provided the placenta is functioning well, the baby will continue to gain weight. Pregnancy is normally between 37 and 42 weeks in length (from the first day of your last period), which is typically known as around nine months – although it is actually a little more than that. You may hear your pregnancy described in three sections, commonly referred to as trimesters:

• 1st trimester (1-12 weeks)
• 2nd trimester (13-28 weeks)
• 3rd trimester (29 weeks to the birth).

Once your due date is confirmed, you can enter it on the Home page, or into the About me section in this app.