The objective was to assess the occurrence of miscarriages, low birth weight, and karyotype abnormalities found with low and elevated maternal serum alpha-fetoprotein (MSAFP) among women who had genetic amniocentesis performed. A retrospective study of 2,159 women who had MSAFP analysis prior to amniocentesis was conducted. Pregnancy outcomes were obtained from record review and physicians follow-up. Limits of MSAFP used in analysis were <0.5 adjusted multiples of the median (MOM) (lower levels) and >2.0 MOM (upper levels). Autosomal trisomy was found in 1.6% with low, 0.9% normal, and 0.6% with elevated MSAFP values. Sex chromosome abnormalities were present only in patients with normal MSAFP, [45X (n = 6), 47XXY (n = 2), 69XXX]. Of five open neural tube defects, four had elevated MSAFP and one had a normal value. Omphalocele was identified in four patients, two with normal and two with elevated MSAFP. Gastroschisis was found in one low and one elevated MSAFP. Amniotic fluid alpha-fetoprotein (AFAFP) values did not correlate with MSAFP values. Patients with low MSAFP levels had a greater prevalence of abnormal karyotype (19 of 249, prevalence = 0.076) than patients with an elevated MSAFP level (2 or 166, prevalence = 0.012 OR (odds ratio) = 0.20 (P value = 0.024) when unadjusted for maternal age, and OR = 0.09 (P value = 0.001) when adjusted for maternal age. Spontaneous abortion occurred more often in patients with elevated (4 of 166, or 4%) than normal or low (20 of 1948, or 1%) values of MSAFP (odds ratio 4.32, P = 0.020 when adjusted for maternal age). Birth weight below 2,500 g was present less frequently with low or normal MSAFP (136 of 1,760, or 7.7%) than in elevated MSAFP (21 of 144 or 14.6%) (odds ratio 2.04, P = 0.005, unadjusted; and odds ratio = 2.32, P = 0.003, adjusted for maternal age). Female fetuses were present more often with low MSAFP (136 of 249, or 55%) than elevated levels 43% (71 of 164, or 43%; P = 0.024). We conclude that patients undergoing genetic amniocentesis with MSAFP <.5 MOM are less likely to miscarry, deliver a low birth weight newborn, or have a male infant than patients with MSAFP levels >2.0 MOM.