Much hoopla surrounds this mid-pregnancy ultrasound, as it's generally thought of as the big Gender Reveal*. While it's true that this is when they can see those parts if you want to know, there's also a lot more that goes on. I think it's important that that not get lost in all the what-are-we-having frenzy, so I wanted to go through a little more on what they're looking at/for, and why, in advance of this event. [Interesting note: in some areas/countries, there are policies that prevent practitioners from revealing a baby's sex to its parents. So think about that today.]
Before moving on from those parts, you can read here if you want to know more about how the sex is ascertained from ultrasound images. It ain't just the presence or absence of a dangle, folks. Furthermore, everything in there looks like a penis, so it's easy to be fooled--especially at your earlier scans.
This scan--some people's only major ultrasound--is usually performed between 18 and 20 weeks. Ours will be at 19 weeks. At this point, all of baby's major bits and pieces have formed, and any abnormalities can be detected. This window of time is ideal because baby is big enough to see all the parts in question, but isn't yet so big that s/he scrunches up and makes looking around difficult. Ultrasound becomes less informative as baby gets bigger in the second half of pregnancy.
It has been demonstrated in multiple studies across multiple countries that there are significant differences in infant mortality when anatomy scans are performed. Identifying fetuses with anatomical abnormalities before birth is important because they can then be delivered in the appropriate hospital environment with a prepared medical team. For example, if you live in a rural area, preparations can be made in advance for delivery at a hospital with a high-quality NICU. Furthermore, you can be referred to specialists to gather more information about the particular condition.
They're looking for a lot, but here are some highlights:
- measurement of the head, length, and long bones to make sure baby is growing appropriately
- unusual development or proportions can indicate a variety of issues that merit further investigation
- a survey of all the major organs: the brain, spine, four chambers of the heart, bladder, stomach, both kidneys, and--of course--the how-ya-doin's.
- it is worthwhile to know of any defects here at this point in the event that baby will need major surgery upon delivery (e.g., in the case of a congenital heart defect). Some corrective surgeries can even be performed in utero.
- the fetal face, eyes, lips, skull, and jaws to ensure they are normal or identify a cleft lip/palate
- the umbilical cord
- you (I) should have a three-vessel cord: two arteries and a vein
- the location of the placenta
- fetal heart rate
- level of amniotic fluid
Visual aid: Click here for a good video of a little 20-weeker (not mine) and explanation of the different aspects and types of ultrasound. I'm sorry I could not embed the video.
The sonographer will take freeze frames of all the relevant shots, and they will be kept in the baby's file.
The most common issue that is discovered is the location of the placenta (placenta previa). If the embryo implanted low in the uterus, the placenta, which is a major vascular structure, can develop in a position that is partially or completely covering the cervix. In other words, it's blocking the baby's way out. Often, monitoring is warranted, but placentas (is that the plural?) can move as the uterus grows, so it might resolve on its own. A complete previa is bad news bears and requires a C-section as soon as the baby is considered term. If this were olden times, you'd probably be toast.
For the record, mine was checked at the 12-week scan and seemed to be in a totally acceptable location at the back of the house. Of further interest (maybe not to you...kudos for reading this far): a placenta that attaches to the front of the uterus is called an anterior placenta and it forms a sort of cushion, so moms with this placement first feel baby move much later in pregnancy. Just one factor that accounts for all the individual differences that are reported.
So, as mentioned, our scan is at 19 weeks. Now you know the low-down. We will be finding out the sex, but we'll be getting a lot of other important information as well--and our primary objective is making sure that everything looks ok, and making a plan if it doesn't.
*On "gender" vs. "sex": Sex is a biological concept that refers to the parts (i.e., male or female), while gender is those elements that are socially or culturally constructed. So we are really talking about sex here, and that is the proper term to use. However, for whatever reason (being uncomfortable with the word?) most people say "gender" in this context. This matters to a lot of people--mostly adults. I'm not going to judge, and I sometimes switch between the words myself in conversation, but...the more you know.
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