How accurate are dating scans at 16 weeks
The earlier age at delivery of multiple gestations is a reflection of the increased incidence of preterm labor and obstetric intervention for complications such as preeclampsia, abruptio placentae, fetal growth restriction, and increased risk for stillbirth that occurs as the number of fetuses increases [30-33]. Mongelli M, Wilcox M, Gardosi J.: Estimating the date of confinement: ultrasonographic biometery versus certain menstrual dates. The tendency for multiple gestations to be delivered earlier than singleton pregnancies should not be interpreted that multiples should be assigned an earlier estimated due date. In cases where the date of conception is known precisely, such as with in vitro fertilization, the EDD is calculated by adding 266 days to the date of conception. American College of Obstetricians and Gynecologists. Ultrasound uses the size of the fetus to determine the gestational age (the time elapsed since the the first day of the last menstrual period). The American College of Obstetricians and Gynecologists.
Doppler Ultrasonography The fetal heart can be heard using Doppler ultrasound by 10 to 12 weeks in most patients . Savitz DA, Terry JW Jr, Dole N, Thorp JM Jr, Siega-Riz AM, Herring AH. A full term pregnancy is considered to be 39 to 40 6/7 weeks regardless of the number fetuses being carried . Chervenak FA, Skupski DW, Romero R, et al: How accurate is fetal biometry in the assessment of fetal age? Chorionic gonadotropin secretion by human embryos in vitro. Generally, by week 18, the ultrasound technician should be able to clearly identify the sex (if the positioning of the baby permits).However, if you’re still unable to find out for certain by the 18 week mark, you should be be able to easily find out the sex if you choose to have another ultrasound later on in the pregnancy.