ASSOCIATION OF IN-UTERO BEHAVIORAL-PATTERNS OF TWINS WITH EACH OTHER AS INDICATED BY FETAL HEART-RATE REACTIVITY AND NONREACTIVITY

Prospective analysis of 75 pairs of nonstress tests (NSTs) obtained si multaneously from both members of 35 twin gestations was performed to quantitatively assess the incidence of simultaneous periods of fetal h eart rate (FHR) reactivity and nonreactivity of twins. Comparative ana lysis of the paired NSTs was used to compute rates of simultaneous fet al heart rate reactivity and nonreactivity. Statistical analysis invol ved comparison of weighted averages of these rates, using sequence len gths as weights. Weighted standard deviations were used to describe va riability between sets of NSTs. Trend analysis was performed using wei ghted linear regression to calculate slopes for pairs of twins with th ree or more repeat NSTs. Groups of twins were compared by performing a variance stabilizing transformation on the appropriate rates, and usi ng a two sample t test to compare the means of transformed data. Analy sis of this data revealed that twins exhibited similar in utero fetal heart reactivity and nonreactivity as indicated by simultaneous electr onic fetal monitoring during 79.90% +/- 1.62 (SD) of the time monitore d. The incidence of periods of simultaneously reactive FHR and simulta neously nonreactive FHR were 11.79% +/- 1.02 and 68.10% +/- 2.17, resp ectively, irrespective of gestational age. These data confirm the hypo thesis that periods of FHR reactivity and nonreactivity of twins are s trongly associated with each other.