Twin Fetal Weight Chart: Estimated Growth Week by Week

The ultrasound-based twin fetal weight charts below are based on a twin study from 2015.  It was published in the American Journal of Obstetrics & Gynecology and adds significantly to the field of fetal growth assessment in twins.

A total of 642 twin fetuses – with a total of 3078 ultrasound observations – were included in the study. Researchers developed a twin fetal weight chart for dichorionic twins in the second half of pregnancy. They also developed a twin fetal weight chart for monochorionic twins.

What does the study show?

The study showed, as expected, that monochorionic twins were consistently smaller than dichorionic twins. It also reaffirmed that twins generally are smaller than singletons.

The study showed twin fetal growth accelerates in the second trimester and continues in a linear pattern in the third trimester until term. This reduction in fetal growth is significant, particularly in the third trimester, compared with singletons.

It concluded that dichorionic twins deviates from singleton reference charts at approximately 32 weeks. Monochorionic twins deviates at 28 weeks. These deviations are one of the reasons why a singleton fetal weight chart shouldn’t be applied to twins.

The normal declaration of growth in twins can seem like an issue, even if it isn’t.

How do I read a twin fetal weight chart?

Fetal growth is better monitored with a doctor.

A twin fetal weight chart shouldn’t be used in isolation without all the other important pregnancy monitoring visits. Also be aware that there’s nothing wrong with your children being below the median weight. 

The median weight is the value for which 50 percent of the fetuses are bigger, and 50 percent are smaller. It  separates the higher half from the lower half.

To give you a better sense of how small or big your babies are, we’ve also included the 10th and 90th percentile.

What’s the 10th and 90th percentile?

If your babies estimated weights are equal to or less than the weight indicated as the 10th percentile, it means that your babies are among the smallest 10 percent. 

If your babies estimated weights are equal to or above the weight indicated as the 90th percentile, your babies are among the biggest 10 percent.  

If you’re worried about the growth of your babies, it’s important that you consult your doctor or healthcare provider.

Growth of twins is an important characteristic to be monitored along with other variables like The Fetal Non-Stress test (NST monitoring).

Estimated fetal weight in dichorionic twins

Estimated fetal weight in monochorionic twins