Congratulations! This week marks the half way point of your pregnancy. It has been 18 weeks since the date of conception and your baby's crown-to-rump length is 5.6 to 6.4 inches. The fetus weighs about 9 ounces and your belly definitely has an obvious bulge. Your waistline has expanded and is no longer visible. Your uterus has now moved up enough that it is pushing your abdomen outwards. The top of your uterus is even with or just below your navel.
Sex organs are showing clearly on this girl
For the remainder of your pregnancy, the growing uterus puts pressure on your lungs, stomach and kidneys. This will make you feel short of breath, the need to urinate more frequently and can cause indigestion. The added pressure on your abdomen can also cause your bellybutton to protrude and cause an `outy` instead of an `inny`. Many pregnant women begin to notice stretch marks around this time as well. Your abdominal muscles are being stretched and pushed apart as your baby grows inside of you.
Your baby's skin begins to thicken this week and will develop four layers. Your baby's sebaceous glands secrete a waxy substance called vernix caseosa. Your baby will be born with this wax and it will look like paste. The vernix caseosa is crucial because it protects the fetus' fragile skin from the continuous immersion in amniotic fluid. Lanugo hairs secure the vernix caseosa in place and it is thick around the eyebrows. Scalp hair and toenails are beginning to form at this point. Hair can also be seen on the upper lip and eyebrows.
Around twenty weeks, most doctors will order a routine ultrasound to check the baby's development. Measurements will be taken and the sonogram technician will check to make sure there are no defects or abnormalities. Your ultrasound technician can also see howlong your cervix is and can tell you approximately how much your baby weighs at this time. Most expectant women also find out the sex of their baby during this time! If your sonographer does not offer pictures, ask them for a copy of the photos.
(現在可以估計體重出來啦!! 真有趣，雖然不知道子宮頸的長度跟體重有甚麼關係，不過就等著囉!! 還有大家都很關心的男生女生，明天就會知道啦!!!!!!!)
What will I be able to see?
Most hospitals allow you to watch the scan, which takes about 20 minutes, as it is being performed. If you haven't already had a scan in this pregnancy, the sonographer will check that there is only one baby, and confirm your due date.
The sonographer will point out your baby's heartbeat and parts of his body, such as his face and hands, before looking at him in detail.
It may be hard for you to make out your baby's organs, because the sonographer will look at them in cross section.
Your baby's bones will appear white on the scan and his soft tissues look grey and speckled. The amniotic fluid surrounding your baby will look black.
After showing you your baby on the screen, some sonographers will turn the screen away for the rest of the scan and show you views at the end. Some hospitals have a second monitor at the foot of the couch so that you can watch the entire scan.
By 20 weeks, it's often possible for you to find out whether your baby is a boy or a girl, but not all hospitals will tell you. If you want to know, ask your midwife about your hospital's policy.
What will the sonographer look at?
The sonographer will examine all your baby's organs and take measurements (FASP 2010). She will look at:
- The shape and structure of your baby's head. At this stage severe brain problems, which happen very rarely, are visible. (腦部發展健全)
- Your baby's face to check for a cleft lip. Cleft palates inside a baby's mouth are hard to see and are not often picked up. (是否有兔唇)
- Your baby's spine, both along its length and in cross section, to make sure that all the bones align and that the skin covers the spine at the back. (脊椎骨骼發展，皮膚是否完整覆蓋)
- Your baby's abdominal wall, to make sure it covers all the internal organs at the front. (腹腔是否涵蓋所有臟器，不是很懂@@)
- Your baby's heart. The top two chambers (atria) and the bottom two chambers (ventricles) should be equal in size. The valves should open and close with each heartbeat. (四個心室是否一樣大小，瓣膜隨著心跳一開一關)
- Your baby's stomach. Your baby swallows some of the amniotic fluid that he lies in, which is seen in his stomach as a black bubble. (北鼻的胃)
- Your baby's kidneys. The sonographer will check that your baby has two kidneys, and that urine flows freely into his bladder. If your baby's bladder is empty, it should fill up during the scan and be easy to see. Your baby has been doing a wee every half an hour or so for some months now! (兩個腎，尿液流進膀胱，北鼻現在每半小時尿一次!)
- Your baby's arms, legs, hands and feet. The sonographer will look at your baby's fingers and toes, but not count them. (小手小腳，自己要一隻一隻仔細的數!)
As well as this detailed look at how your baby is growing, the sonographer will check the placenta, the umbilical cord and the amniotic fluid. (檢查胎盤位置、臍帶跟羊水)
The placenta may be on the front wall
(anterior) or the back wall of your uterus (posterior), usually near the top (or fundus). If the placenta is near the top, it may be described as fundal on your scan notes.
The placenta will be described as low if it reaches down to or covers the neck of your uterus (your cervix). If the placenta is lying low in your uterus
, you'll have another scan in the third trimester
to check its position. By then, it's likely the placenta will have moved away from your cervix.
It is possible to count the three blood vessels
(two arteries and a single vein) in the umbilical cord, but your sonographer may not do this. It's not routine procedure. She will check to see that's there's enough amniotic fluid
for your baby to move freely, though. (自己最好能數到臍帶的三條大血管，最後，羊水量是否足夠)
During the scan, the sonographer will measure parts of your baby's body, to see how well he is growing. The sonographer will measure your baby's:
- head circumference (HC)
- abdominal circumference (AC)
- femur or thigh bone (FL)
The measurements should match up to what's expected for your baby, given his anticipated due date. The due date will have been established at your dating scan
. If your anomaly scan is the first scan you've had, it will be used to establish a due date.
Which abnormalities can be seen on the scan?
Sonographers have a list of conditions to look out for. The conditions are on the list either because they are very serious and may even mean a baby can't survive, or because they are treatable after birth.
If the conditions are treatable, it will help the hospital team to know in advance. The team can then make sure your baby has the right care as soon as he's born.
Some conditions are easier to spot than others; some are hard to see at all. Most of the conditions on the list are very rare. Here's the list of conditions, and the percentage chance of your sonographer seeing each one, if your baby has it:
- Absence of the top of the head (anencephaly): 98 per cent
- Cleft lip: 75 per cent
- Defect of the abdominal wall (exomphalos): 80 per cent
- Defect of the abdominal wall (gastroschisis): 98 per cent
- Missing or very short limbs: 90 per cent
- Defect of the spinal cord (spina bifida): 90 per cent
- Major kidney problems (missing or abnormal kidneys): 84 per cent
- Hole in the muscle separating chest and abdomen (diaphragmatic hernia): 60 per cent
- Excess fluid within the brain (hydrocephalus): 60 per cent
- Edwards' syndrome or Patau's syndrome (chromosomal abnormalities): 95 per cent
- Major heart problems (defects of chambers, valves or vessels): 50 per cent
Some conditions, including heart defects and bowel obstructions, may not be seen until later in your pregnancy.
Having your anomoly scan will most likely rule out all these conditions, as the vast majority of babies are born healthy.
What if there are signs of a problem?
Most problems that need repeat scanning are not serious. About 15 per cent of scans will be done again for one reason or another.
The most common reason is that the sonographer has not seen everything she needs to see. This may be because your baby is not lying in a good position, or you are overweight, in which case the scan should be repeated at 23 weeks (FASP 2010).
If your sonographer finds or suspects a problem, you will be told straight away. You should have an appointment for a scan with a fetal medicine specialist within 72 hours.
If doctors suspect that your baby has a heart problem, you will be asked to come in a fetal echo scan. The fetal echo scan will take a detailed look at your baby's heart.
If any scan reveals a serious problem, you should be given plenty of support to guide you through all the options. Although such serious problems are rare, some families are faced with the most difficult decision of all, whether to end the pregnancy.
Other problems may mean a baby needs surgery or treatment after birth, or even surgery while he is still in the uterus. There will be a whole range of people to support you through any difficult times, including midwives, obstetricians, paediatricians, physiotherapists and the hospital chaplain.