Rhesus isoimmunization in twin gestation

Craniofacial abnormalities in twins at tygerberg hospital, craniofacial unit

There is no article in the literature correlating only craniofacial abnormalities in twins. Since 1985 the Tygerberg Craniofacial Unit has treated nine pairs of twins. In this retrospective study, the authors correlate the craniofacial and systemic anomalies with the specific twin type.

BACKGROUND

The frequency of human twinning varies from 1 in 30 to 1 in 150 pregnancies. These can be monozygotic (MZ) or dizygotic (DZ). Monozygotic or identical twins occur when a single ovum is fertilized, so the twins possess an identical set of nuclear genes. DZ twins result from the fertilization of two separate ova.

FINDINGS

Of the nine sets of twins, six were MZ (identical) and three DZ. Twelve patients presented with craniofacial abnormalities (CFA), which ranged from deformational plagiocephaly, scaphocephaly, trigonocephaly, to frontonasal dysplasia. Craniosynostosis was the most common CFA. Associated abnormalities included facial, limb, and cardiac defects.

CONCLUSION

Twins with CFA are rare. The authors found that MZ twins are affected more and are more likely to have both siblings affected. DZ twins are affected less and are unlikely to have a co-twin affected.

Fetomaternal AB0 incompatibility and erythroblastosis fetalis

Ninety-one of 330 fetuses undergoing intrauterine fetal transfusion (IUT) had sufficient residual fetal red cells in their cord blood samples that their AB0 blood groups could be determined. Ten of the 91 (11%) were AB0 incompatible with their mothers. The degree of Rh disease was severe in all 10. Three were hydropic in utero; 5 had the syndrome of hepatocellular damage; in 6, IUT were required between 22 and 26 weeks gestation. The expected incidence of AB0 incompatible pregnancies in which the fetuses required IUT if AB0 incompatibility had no effect on severity of Rh disease, is 9.7% versus the 11% observed. AB0 incompatibility has no effect on ameliorating severity of erythroblastosis after Rh immunization has developed. AB0 incompatibility between mother and father should not be taken into account when making decisions regarding the management of an Rh immunized pregnancy.

Alloimmunization in twin pregnancies

Of 118 twins born of 59 alloimmunized mothers from 1944 to 1984, 65 were Rh-positive and six died. One twin in one of the 59 sets and four sets of twins referred from elsewhere underwent intrauterine fetal transfusion. The Manitoba twin and two pairs of the four referred sets survived. Fetal transfusions were begun at 22 2/7 and 24 1/7 weeks' gestation in one surviving set and 23 3/7 weeks in both twins of the other surviving set. Three twins of the four who died were hydropic at referral. There would have been a 62.5% chance of survival if they had been referred at 23 weeks' gestation. ABO incompatibility in one twin of three sets had no effect on the amelioration of severity of Rh disease. In three sets, gross hemoglobin disparities were due to twin-to-twin transfusion. Differences in degree of severity of disease in the other four dichorionic sets may have been due to differences in sex, Rh constitution, amount of fetal erythropoiesis, and fetal hepatocellular function.

Use of indigo carmine for twin amniocentesis and its effect on bilirubin analysis

Indigo carmine is used commonly to mark the first-entered amniotic sac in twin amniocenteses. The presence of this dye significantly affects amniotic fluid bilirubin analysis. A method of chloroform extraction is recommended for determination of bilirubin in amniotic fluid previously contaminated by indigo carmine.