Month 4: Weeks 13-16

Doctor visits

Woman in lab doing blood work

In addition to the usual charting of your weight, blood pressure, protein and glucose levels; measuring the size of your uterus; and listening to your baby’s heartbeat, your doctor may do a test to see how well your baby is developing.

Quad screen

Your doctor will test your blood to measure four substances that normally come from a baby’s blood, brain, spinal fluid and amniotic fluid. The test tells whether the baby has an increased risk of developmental or chromosomal conditions, such as spina bifida or Down syndrome. The test results indicate only whether you have an increased risk of these conditions, not whether your baby actually has the condition. An ultrasound or amniocentesis may be recommended to confirm or rule out a diagnosis.

The optimal time for quad screening is during weeks 16 to 18.

Your baby

Month 4 baby progress illustration

There is a lot of growing going on during the second trimester! By the fourth month, all of your baby’s organs, muscles and nerves are well developed and working together. The reproductive systems are developing quickly now: the prostate in boys and the ovaries in girls. Bone and bone marrow are developing, and transparent skin is beginning to form. You should be able to hear your baby’s heartbeat during your prenatal visit this month. At the end of the fourth month, your baby is about 4 to 5 inches long but weighs only around 3 ounces.  


Join Our Newsletter Back to Top