On April 30, 2004, Atlanta Maternal-Fetal Medicine joined the Obstetrix Medical Group. The Obstetrix Medical Group is the nation's largest provider of maternal-fetal-newborn care, with Atlanta Maternal-Fetal Medicine being the first MFM practice from the Southeast to join the practice.

DIRECTIONS

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TWIN PREGNANCIES

Twin pregnancies are found in three varieties: (1) two placentas with two sacs (most common), (2) one placenta with two sacs, and (3) one placenta with one sac (least common). Ultrasound can be used to determine the most likely kind of twin gestation. The technology used includes examining the number of sacs on the ultrasound, counting the layers of membranes, and looking at the area of attachment of the fetal membranes to placenta(s). 

All twin pregnancies with one placenta are considered identical. All non-identical pregnancies have two placentas and two sacs. The tricky part is that some identical twins have  two placentas and two sacs. These twins are usually discovered as identical as they grow older because they look alike physically. 

Usually when most people think of twins, we think of identical twins. Surprisingly, the most common kind of twins are the non-identical twins. Approximately two-thirds of twins are non-identical (1-2% of pregnancies not conceived by infertility treatment). Of the one-third of twins who are identical, approximately two-thirds have two sacs, and one-third share the same sac. Twins with one placenta and one sac are the rarest kind of twins, occuring in 102 per thousand pregnancies.

This image shows the four layers of membranes in a non-identical twin pregnancy. The top and bottom layers are the outside membranes (chorion). The inside two layers are the amniotic membranes. The pathologist counts the number of membranes when examining the placenta after delivery. This helps establish whether the pregnancy was likely to have been identical or non-identical.

VIEWING FETAL EXTREMITIES 

There are a number of legitimate indications for imaging the fetal extermities during pregnancy: excluding limb reduction defects, screening for Trisomy 18, and assessing fetal muscle  tone. Although patients often ask whether the fetus "has all of its fingers and toes", imaging the fetal digits is extremely difficult at all gestational ages. Once in a while, a photogenic fetus will give you that once-in-a-lifetime picture, such as the "peace sign" seen right.

CLINICAL DISCUSSION HIGHLIGHTS:

Recently, several clinical studies have suggested that ultrasound studies during pregnancy are not necessary for the successful completion of a low-risk pregnancy. Therefore, this has brought to question the usefulness of the ultrasound as a clinical entity during pregnancy. This issue of  Clinical Discussions will review the most common reasons and high-risk indications for follow-up ultrasounds.

The human papilloma virus (HPV), a member of the Papovaviridae family, is a double stranded DNA virus with more than 60 subtypes identified; 20 of these subtypes affect the epithelium of the genital tract. Condylomata acuminata (subtypes 6 and 11) and cervical dysplasia (subtypes 16, 18, 31, 33 and 35) are the most common clinical manifestations of HPV infections. With respect to pregnancy, the increased prevalence, potential for precluding safe vaginal delivery, and possible maternal-fetal transmission of HPV are reviewed in this issue of  Clinical Discussions.