Origins of Stillbirth and Miscarriage in the Context of Twinning

Colin Korlesky
University of Wisconsin - Madison

Colin Korlesky, Elizabeth McPherson
Center for Human Genetics

Research area:  Genetics

Background: Perinatal mortality among twins is 4-fold higher than for singletons, a growing concern given twin pregnancies increased from 18.9 to 33.9 per 1000 births since 1980. Though twins are known to be at increased risk for pre- and peri-natal complications, more information on twin demise is needed to plan surveillance for multifetal pregnancies.

Methods: The Wisconsin Stillbirth Service Program (WiSSP) database includes 3062 2nd trimester miscarriages and stillbirths including 169 twin pairs [20 fraternal/dizygotic (DZ), 93 identical/monozygotic (MZ), and 56 unknown zygosity (UK)] from 1982-present. To better understand the factors that contribute to 2nd trimester miscarriage and stillbirth in multiple gestations we compared gestational age, birthweight, placental weight, and cause of death of WiSSP MZ and DZ twins with liveborn twins and WiSSP singletons.

Results: WiSSP twinning rate was 55/1000 or approximately double the average population twinning rate over the study period. This increase was due almost entirely to MZ twins (129 pairs after Weinberg estimation), with twin-twin transfusion (TTT) being the primary cause of MZ death. Regardless of TTT, MZ twins had comparable birthweights but larger placentas than DZ pairs, implying inherent MZ placental circulatory inefficiency. Median gestational age at death was lower for MZ twins (23 weeks) versus DZ twins and singletons (28 weeks). MZ cause of death was similar to singletons with TTT removal. Among DZ and singletons, placental/maternal causes were greater in DZ and fetal causes greater in singletons. 

Conclusions: Increased MZ mortality begins early and is largely due to TTT, indicating that improved TTT screening and earlier intervention may be lifesaving. However, low fetal/placental ratios for MZ twins after exclusion of TTT and increased placental abnormalities for DZ twins versus singletons suggest underlying placental insufficiency in all twins that not only increases pre- and peri-natal mortality but also programs lifelong problems in surviving twins.