Main effect. In the design of experiments and analysis of variance, a main effect is the effect of an independent variable on a dependent variable averaging across the levels of any other independent variables. The term is frequently used in the context of factorial designs and regression models to distinguish main effects from interaction effects.
The most commonly used method to find out the sex of your baby is ultrasound or sonogram. This method is most accurate between 18-22 weeks. It is normally done at the fetal anatomy survey or mid-pregnancy ultrasound, done in the mid-second trimester. At this point it is usually easier to tell the sex of the baby.
Around 12 weeks gestational age, the external genitalia may be formed enough to determine sex. A diagnostic ultrasound is performed around 18 and 20 weeks. Many people find out if they are having a girl or boy during this time. The ultrasound tech will take measurements of the fetus and check for any abnormalities.The tech will then look at the genitals to determine if it is a boy or girl.ome people choose to get a 4D ultrasound, which is a detailed and lifelike look of the fetus. If you are unable to tell the sex of your baby at your routine ultrasound, this may be an option for you.