If you still don’t know your baby’s gender or want to confirm the doctor’s guess, now is the time. When entering the 18th week of pregnancy, you will be able to get a morphology scan – keep in mind this scan is more likely to be suggested in the 20th week. During this exam, the sonographer will analyze the entire body structure of your baby: internal organs such as stomach and kidneys, spine, bones, arms, legs, and, of course, will be able to give the verdict: boy or girl since the genitals are already formed.

When do sex organs develop?

The external sex organs start to develop between 11 and 16 weeks. Before that time, the fetus’s body has a structure called a genital tubercle, and depending on its angle in relation to the spine, horizontal or vertical (at least 30 degrees) may be indicative of female or male genitals.

When the time comes for the “20-week ultrasound,” external sex organs will be developed enough to differentiate between a boy or girl.

Is it a certain thing?

Sometimes, the difference is subtle, since the penis is still tiny (only millimeters) and can be confused with the girl’s clitoris. Also, it will depend on the position in which the baby is at the time of the ultrasound. It may be impossible to tell the difference if, for example, part of the umbilical cord happens to be between the legs. If that is the case, you better wait until the next tests to be more certain

Is there a fail proof way of finding out the biological sex before?

Well, yes! There is a way to test the mother’s blood and determine the baby’s biological sex. NIPT is (noninvasive prenatal testing) is a blood test used to screen for Down syndrome and a few other chromosomal conditions and can identify fetal sex. In some countries, it can be done as soon as eight weeks of pregnancy; in the US, doctors prefer to wait until 9-10 weeks. The test looks for the Y chromosome in the mother’s blood: if it’s there, it’s a boy, if not, girl. It’s guaranteed because fetal cells circulate through the mother’s body.

Biological gender prediction kits are available at drugstores and claim to work as early as six weeks into a pregnancy, but they are not 100% accurate.

Read Next:

+ Important exams for the second trimester

+ How to set up your layette checklist

+ The development of the baby week 18

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