Catecholamine levels and associated cardiovascular responses were determined in 21 control and 30 term infants with meconium-stained amniotic fluid (MSAF). Cord arterial blood was obtained for determination for norepinephrine (NE) and epinephrine (EPI) levels; cardiovascular measurements included heart rate and systolic blood pressure at 30 min. Pregnancy was uncomplicated in all cases. The total length of labor 964 +/- 402 versus 555 +/- 312 min (P < 0.001) and active phase of labor 300 +/- 261 versus 135 +/- 104 min (P < 0.001) were significantly longer in MSAF infants when compared to controls. The 1 min Apgar score was < 7 (range 1-6) in 11 of 30 MSAF infants versus 0 of 21 control infants; these 11 infants required positive pressure ventilation for approximately 60 s secondary to transient respiratory depression (RD). The 5 min Apgar score was > 7 in 49 of the 51 infants. Infants with MSAF exhibited a higher PaCO2 (6.89 +/- 1.17 vs 6.24 +/- 1.17 mmHg; P < 0.02) and lower pH (7.25 +/- 0.06 vs 7.29 +/- 0.05; P < 0.02) compared to controls. Infants with transient RD demonstrated the most marked arterial blood gas differences, i.e., PCO2 7.41 +/- 1.30 mmHg (P < 0.001), pH 7.21 +/- 0.07 (P < 0.001) and base deficit -6 +/- 4 versus -3 +/- 2.8 (P < 0.001) when compared to controls. NE and EPI levels were significantly higher in MSAF versus control infants, i.e., 12600 +/- 3040 versus 3740 +/- 1000 pg/ml (SEM) (P < 0.02) and 1550 +/- 250 versus 620 +/- 130 pg/ml (P < 0.001) respectively.(ABSTRACT TRUNCATED AT 250 WORDS)