Almost every woman with a visible baby bump has been asked whether she is having a girl or a boy. The gender of the baby is determined at conception, although differentiation of the sexual organs does not begin until the middle of the sixth week of gestation, according to the NOVA article, "How Is Sex Determined?" Various tests can inform parents of the baby's gender.
Chorionic Villus Sampling
Chorionic villus sampling is generally performed at the end of the first trimester, as early as 10 weeks but more often between weeks 10 and 12 after your last menstrual period, according to the WebMD article, "Pregnancy and Chorionic Villus Sampling." The test removes cells from the edge of the placenta and is used to detect various conditions such as Down syndrome, sickle cell anemia, cystic fibrosis and Tay-Sachs disease, but it can also reveal the baby's gender. The test may cause miscarriage, vaginal bleeding or fluid leakage and, in rare cases, damage to the baby's fingers and toes. Obstetricians might recommend the CVS for pregnant women who are over 35, have abnormal genetic testing results or have had a previous baby with birth defects.
Sampling Amniotic Fluid
An amniocentesis samples amniotic fluid using a needle inserted into the uterus through the abdominal wall, generally performed in the 16th week of pregnancy or later. The risk for miscarriage with an amniocentesis is less than the risk from the CVS, according to WebMD. The test is performed for the same reasons your doctor might recommend the CVS or if you have an abnormal ultrasound. The amniocentesis identifies more genetic diseases than the CVS and also reveals the gender of the baby.
Many obstetricians and midwives recommend a midpregnancy ultrasound around the 18th to 22nd week of pregnancy. This is noninvasive and less risky than the CVS or amniocentesis and can reveal the baby's gender if the baby cooperates during the scan, according to Dr. Elizabeth Pryor, MD, FACOG, in the Parents article, "Q&A: How Soon Can You Find Out Baby's Sex?" However, the technician must be able to view the baby's genitals to determine gender, and some babies seem determined to keep it a secret by not positioning themselves in a way to see the genital area.
An uncommon option that may predict the baby's gender early in pregnancy is known as Ramzi's Method and relies on 2-D sonograms performed at six weeks gestation. The procedure uses the placement of the chorionic villus or placenta to predict the baby's gender. Placentas located on the right side of the uterus are male 97.2 percent of the time and those located on the left side of the uterus are female 97.5 percent of the time, according to an article published on ObGyn.net, "The Relationship Between Placental Location and Fetal Gender (Ramzi's Method)." The author of the study, Dr. Saad Ramzi Ismail, recommends that parents ask the sonographer to identify the location of the placenta.