Table 1. Summary of samples and overall abnormality rates per trimester.

	Specimens and abnormality rate per trimester
	No. specimens	%	No. Abn	%
1st trimester	272	42.3	112	41.2
2nd trimester	258	40.1	44	17.1
3rd trimester	113	17.6	11	9.7
Total	643		167