Weather and childbirth: a further search for relationships.

Previous attempts to find relationships between weather and parturition (childbirth) and its onset (the beginning of labor pains) have revealed, firstly, limited but statistically significant relationships between weather conditions much colder than the day before, with high winds and low pressure, and increased onsets; and secondly, increased numbers of childbirths during periods of atmospheric pressure rise (highly statistically significant). To test these findings, this study examined weather data coincident childbirth data from a hospital at Bryan-College Station, Texas (for a period of 30 cool months from 1987 to 1992). Tests for (1) days of cold fronts, (2) a day before and a day after the cold front, (3) days with large temperature increases, and (4) decreases from the day before revealed no relationship with mean daily rate of onset. Cold days with high winds and low pressure had significantly fewer onsets, a result that is the opposite of previous findings. The postulated relationship between periods of pressure rise and increased birth frequency was negative, i.e., significantly fewer births occurred at those times--again, the opposite of the apparent occurrence in an earlier study. The coincidence of diurnal variations in both atmospheric pressure and frequency of childbirths, was shown to account for fairly strong negative associations between the two variables.(ABSTRACT TRUNCATED AT 250 WORDS)