Maternal and Fetal Factors Related to Abnormal Amniotic Fluid Marı´a Luisa Martı´nez-Frı´as,MD Eva Bermejo ElviraRodrı´guez-Pinilla Jaime L.Frı´as OBJECTIVE: The objective of this study was to identify maternal and infant character- istics related to alteration of amniotic fluid volume at birth. STUDY DESIGN: A series of 27,145 consecutive malformed newborn infants from the Spanish Collaborative Study of Congenital Malformations (ECEMC) was analyzed. From this total, 3.01% were found to have oligohydramnios and 3.69% were found to have polyhydramnios. RESULTS: As expected, renal/urinary tract and lung defects were associated with oligohydramnios, whereas esophageal and intestinal atresias, neural tube defects, and other central nervous system malformations were asso- ciated with polyhydramnios. In addition, other defects such as cardiovas- cular anomalies, hydrocephaly, and microcephaly were also related to abnormalities of amniotic fluid volume. After excluding the defects whose association to oligo- or polyhydramnios is well recognized, we compared the frequency of different variables among them and with infants with a normal volume of amniotic fluid. In comparison with infants with normal amniotic fluid volume, the groups with oligo- and polyhydramnios had lower birth weight, shorter gestational age and umbilical cord, higher parental ages, and a greater frequency of sponta- neous abortions. The differences were more marked for weight in new- born infants with oligohydramnios, and for gestational age, umbilical cord length, number of previous pregnancies, and spontaneous abortions in polyhydramnios cases. Placental weight was lower in oligohydramnios cases than in infants with normal amniotic fluid, and higher in polyhy- dramnios cases. Parental consanguinity and twinning were more fre- quent in polyhydramnios. Maternal morbidity was higher in both groups with abnormal amniotic fluid volume, especially for acute diseases such as hypertension, diabetes mellitus, and gestational diabetes. Chromosomal aberrations were more frequent in the oligo- and polyhydramnios groups than in cases with a normal volume of amniotic fluid, which supports the suggestion of performing prenatal cytogenetic analysis in any pregnancy complicated by an abnormal volume of amniotic fluid. CONCLUSION: The fact that all of these results are similar in the control group of healthy infants suggests that at least some of the variables associated with abnormal amniotic volume could be considered as causal factors altering the production of fluid. Amniotic fluid derives from different maternal and fetal structures, including the amnion, chorion, maternal blood, fetal lungs, gastroin- testinal tract, kidneys, and skin. 1–3 It is possible that alterations of one or more of the different sources will alter the amount of amniotic fluid. This is quite clear in relation to some congenital malforma- tions, which are one of the most important causal factors in the ab- normalities of amniotic fluid volume. Among these, the malforma- tions that are most constantly associated with a markedly decreased volume of amniotic fluid are bilateral renal agenesis and obstruction of the urinary tract. Other anomalies, such as esophageal atresia, intestinal atresias, and neural tube defects (NTD), have been associ- ated with an increased volume of amniotic fluid. However, other fac- tors may also modify the quantity of amniotic fluid. 4–9 Here we present the analysis of some maternal and infant charac- teristics, as well as perinatal outcomes, in relation to amniotic fluid volumes in a series of 27,145 consecutive malformed infants identi- fied by the Spanish Collaborative Study of Congenital Malformations (ECEMC). MATERIALS AND METHODS The ECEMC is a congenital anomalies registry with a methodology based in an ongoing hospital-based, case-control study and surveil- lance system. Physicians examine all children born in participating hospitals across Spain during the first 3 days of life to identify major and/or minor/mild defects. For each case, the next nonmalformed infant of the same sex born in the same hospital is selected as a con- trol subject. Once the cases and control infants have been identified (binded to any type of characteristics or prenatal exposures), the same physician interviews the mothers of the case children and control ECEMC (M. L. M.-F., E. B., E. R.-P.) and Departamento de Farmacologı ´a (M. L. M.-F.), Fac- ultad de Medicina, Universidad Complutense, Madrid, Spain; and Department of Pediatrics, University of South Florida, Tampa, FL ( J. L. F.). This work was supported in part by a grant from Instituto de Salud Carlos III, Ministerio de Sanidad y Consumo (Madrid, Spain), and by Fundacio ´ n 1000 Para la Investigacio ´n sobre Defectos Conge ´nitos of Spain. Address correspondence and reprint requests to Marı ´a Luisa Martı ´nez-Frı ´as, MD, ECEMC, Facultad de Medicina, Universidad Complutense, 28040 Madrid, Spain. Journal of Perinatology (1999) 19(7) 514 –520 © 1999 Stockton Press. All rights reserved. 0743– 8346/99 $12 514 http://www.stockton-press.co.uk Original Article              