Today we are proud to announce our first article written by a guest blogger. Doctor Nocere is an acquaintance of ours who had expressed interest in doing a guest spot such as this one, and so penned this wonderful piece on the superstitions of baby sexing (no, it’s not what you think, you dirty, dirty monkeys). Dr. N is a physician, psychiatrist, and avid reader of the comic. He is a geek at heart, a skeptic at brain, and has provided expert consultation on many an occasion. So it is with great pride that I post his work here. Enjoy!

The most frequent conversation we have in my household these days begins with “Do you think it’s a boy, or a girl?” My wife is 16 weeks pregnant with our first child, and we are excitedly waiting for the ultrasound appointment where we determine the sex of the baby.

I can’t tell you how many different people, of different cultures,  ages, and educational backgrounds have told us that they were able to successfully determine the sex of one of their friends’/relatives’ babies based on their theories. While this is often harmless banter, more often than not a pleasantry, I find myself getting annoyed by their lack of humility in the era of evidence based practices.

“The last two people I said were going to have a girl, both had girls! I knew this because they were carrying high and craved sweets!” exclaimed a Master’s-Degree-holding friend of ours.  I found myself making the same face I use when people tell me to turn off the air conditioner because they will catch a cold, or when they ask me if I believe in global warming. These are benign enough examples that I have to actively spend energy to suppress my desire to go into a monologue of why what they are saying doesn’t make sense! The time has come to speak what is on my mind, and write about what I know.

There are many theories or old wives methods to supposedly detect the gender of the unborn child.  There are also many websites that profit from advertising money that allow the parent to answer questions that will lead to the gender.  If you call it entertainment, like paying to watch a movie, that is fine, but there is a huge industry interested in marketing this technique, as well as deep seated ethical quandaries that can arise from the inappropriate use of the ultimate determination.

If you have any one of the following… it’s a boy! Your urine is bright yellow, the baby daddy is also gaining weight, your pillow faces north when you sleep, you crave salty or sour foods, are carrying low, the baby’s heart rate is less than 140 beats per minute, your feet are colder than they were before, your hands are dry, and if you hang a ring/crystal/Pokémon ball over your belly and it moves in circles (instead of side to side).

If, on the other hand, you have morning sickness early on, your urine is a dull yellow, you get more acne, you crave sweets and fruits, you are carrying high, the baby’s heart rate is equal to or greater than 140 beats per minute, your left breast is large than the other, you are gaining weight in your hips and butt, and in general ‘don’t look as good as you normally do’… it’s a girl!

My references for these theories include some of our friends, the guy that sells the newspaper on the side of the highway, the lady at the grocery store, my wife’s hairdresser, and our local shaman.

There is no way that Science (capital S is like capital G for god – just emphasizes my Science is bigger than yours) knows of that can reliably predict the gender of the baby without either a blood, plasma, amniotic fluid, urine test or an ultrasound. Anyone can guess, and will ALWAYS be correct 50% of the time. Right? 50% chance boy, and 50% chance girl. So stop looking at the dullness of your urine, and get that amulet away from my wife!

The popular press recently covered a meta analysis published in the Journal of the American Medical Association. The articles are regarding a meta-analysis of the success of sex determination using cell-free fetal DNA samples obtained by taking blood from the mother. The test is a kit that you take home, get a blood sample from the expecting mother (fingerstick), and mail it back to the lab.

Although sticking a needle into the mother is more invasive than an ultrasound over the belly, the key to this blood test  is that it achieves remarkable sensitivity (proportion of male fetuses with a positive test result) and specificity (proportion of female fetuses with a negative result) much sooner than can be detected by sonography.

The earliest the ultrasound can aid in detection of the gender is around 11 weeks, and gets close to 90% accuracy by the 13th week. The method employed is looking directly AT the genitals. The home blood test can achieve 95% sensitivity and 98% specificity by 7 weeks of gestation. The method is that it detects the Y chromosome sequences in the maternal blood. So if Y chromosomes sequences are found… it’s a boy! (Not if your belly is the shape of a basketball, or if you don’t refuse to eat the heel of a loaf of bread.) If Y chromosomes are absent, that means that you either are having a girl, or that no Y chromosomes were detected. At this point, these blood tests do make mistakes, and are better the later in pregnancy you get tested. A theory is that there is an increased concentration of cell-free fetal DNA in the maternal blood as the baby develops.

As long as you are not one of the 50 million of the uninsured in our country, your insurance will pick up the tab for the ultrasound. The home blood tests costs over $300 once shipping and lab fees are tallied up, and are not covered by insurance. While being able to buy the pink elephant toy when you find out it’s a girl earlier (or for a boy, not that there’s anything wrong with it) may be appealing, the flip side is the economic vampiricism and that ethical boundary of gender selection is being crossed regularly. There are companies that make the home kits that do not sell in countries that have high rates of gender bias towards males. Since the gender can be detected sooner, and at home (i.e. without an ethical doctor’s raised eyebrow) the parents can have elective abortions sooner, with potentially less complications.

We are at an exciting time in laboratory testing, where home kits can tell you if you are the father, if you have HIV, the sex of your child or your predisposition to genetic diseases. We must be responsible and understand why we are doing what we do, and why we say what we say.

Having a baby is a fun and exciting process. If your choice of mitigating anxiety is the employment of mumbo-jumbo-leaf-reading woo, that is fine, but note that as Maki and Nadir at Sci-ence have noted before, simple innocent sounding utterances can have serious consequences.


This post was brought to you by  Ytterbium (Yb).


Here’s a link with info on the Drano Sex Test.