ZINC SUPPLEMENT DURING PREGNANCY AND EARLY LACTATION: A LONGITUDINAL STUDY IN NIGERIAN WOMEN AND THEIR NEW BORN BABIES

Abstract

Pregnant women who were booked at the Lagos Island Maternity Hospital ante-natal clinic and whose gestational periods were between the tenth and fourteenth week were recruited into the study after medical screening for infections and systemic diseases. Subjects were illiterate petty traders from the low socio-economic class but intelligent enough to give personal social, medical/ obstetric histories. The subjects were sufficiently informed to understand and carry out simple instructions. Zinc was supplemented in the form of increased intake of foods rich in zinc by forty-five subjects (CG) with twenty others as control (UG). Zinc sulphate capsules were given out to thirty one subjects (ZG) and eleven other subjects took placebo made of lactose and talc as control (PG).The zinc capsules contained 75.04mg of hydrated zinc sulphate (ZnS04.7H20). This is an equivalent of 17.14mg of elemental zinc which represents 75.4% of the recommended daily allowance of the element for pregnant women. At the first contact, after explanation of the procedures and duration of study to the subject, written consents were obtained. Personal, social, medical and obstetric histories were taken, heights and weight were recorded. 10mls of venous blood was taken for hemoglobin and hematocrit measurements while the plasma collected were later analysed for the concentrations of zinc, calcium, iron, copper, total proteins, albumin and cholesterol. These analyses were repeated at 20th, 28th and 36th weeks of gestation, parturition and post natal period. Twenty four hour duplicate food samples ns eaten at table were collected from subjects at second contact and analysed for zinc contents. At delivery, 10ml of cord blood sample from each baby was collected and analysed for the same Parameters as the mother’s simple. Birth weights, birth lengths and head circumferences were measured. At postnatal clinic, breast milk samples were taken and analysed for the same parameters as plasma. The result of study were analysed to show the mean concentrations of each parameter in each group, the comparison of means between groups in order to show the effects of zinc supplementation age, parity and long term effects of the supplementation on parameters. The means and comparisons of all the parameters in the babies were also analysed to determine the extent of dependency of the fostal values on maternal concentrations. All subjects were aged between 18 years and 42 years with heights ranging from 1.33m to 1.72m. The mean parity was from 2.0± 1.49 in the UG to 2.8± 1.97 in the CG. The daily mean zinc intake was 10.89± 2.22mg in the CG and 10.22± 1.60mg in the UG and 10.08± 1.44mg in the PG with no significance difference but the 27.36± 8.21mg mean total intake during supplementation in the ZG was significantly higher than intakes in all other groups. There were slight weight increases in all groups, highest in the ZG with 11.75kg and lowest in the PG being 7.94kg with the male babies heavier than females. While maternal age and parity did not significantly affect the weight gain during pregnancy, the babies of teenage and primiparous mothers were lighter than those from adult and multiparous mothers. General decline in plasma concentrations were observed with zinc, calcium, iron, hemoglobin, hematocrit, proteins and cholesterol in all groups of mothers despite the supplementation of zinc but in each case, there was a rise in concentration by post natal period, above the values at first contact. Like the maternal weights, copper concentrations increased throughout the period of gestation and then fell below the values at first contact by post natal period. The mean plasma concentration obtained for each parameter in the different groups were similar despite zinc supplementation. Maternal age and parity had effects only on the increase in plasma copper concentrations during pregnancy and not on any other parameters. The babies in the different group also had similar mean plasma concentrations of all the parameters studied, maternal age and parity

notwithstanding and despite supplementation in mothers. Only 53 women (49.53%) had their babies in the hospital while 54 others defaulted. The number of defaulters was even greater in all the groups at post natal period as only 24 women (22.43%) reported. This showed that the maternity care rendered by the hospital had not yet been totally embraced by all the women studied and the community at large.