Haplogroup-associated differences in neonatal death and incidence of low birth weight at elevation: a preliminary assessment.

OBJECTIVE: We sought to assess reproductive fitness differences between mitochondrial deoxyribonucleic acid haplogroups at high altitude. STUDY DESIGN: This study considers differences in outcomes of conception, birth weight, and neonatal mortality rates for 62 women classified according to haplogroups (B or non-B). RESULTS: The number of low-weight births (<2500 g) for the non-B group was significant (P =.019). Mothers in the non-B group reported more spontaneous abortions (P =.171) and stillbirths (P =.301). The difference in conceptions per woman between groups was significant (P =.036). However, no difference in infants alive at 1 month of age was evident. Neonatal death was significant (P =.017). The odds of an unsuccessful outcome among mothers in the B group was compared with mothers in the non-B group and was significant (P =.029). The chance of an adverse outcome, that is, fetal or infant death before 1 month, for mothers in the B group was between 11.1% and 88.7% lower than for mothers in the non-B group. CONCLUSIONS: The neonatal mortality rate for the non-B group was significantly elevated relative to the B group. The molecular basis for these observations is not clear.

Limits of fetal viability. Obstetric considerations regarding the management and delivery of the extremely premature baby.

The maternal-fetal/neonatal considerations regarding management near the limits of viability are becoming increasingly complex. This article presents a data base upon which to formulate clinical decisions. Epidemiologic and financial considerations are discussed, and a perinatal management approach to the more common clinical situations is provided.